Known Locations and Status Updates
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Select an invasive species from the list below to see the locations of known Orange County occurrences, as well as a status update from the chapter. Please do not report known Orange County occurrences. However, all new occurrences of these species should be documented and mapped to either Calflora (preferred) or iNaturalist. Alternatively, you may report these to using the instructions at Reporting an Invasive Plant.
Status updates include information on new occurrences, management activities, updates about the population, successes and failures and other news regarding each invasive species. If you have other updates or corrections, please report them for inclusion to .
For occasional brief summaries of recent invasive plant information also see Invasive Updates.
2022 EMERGENT INVASIVE PLANT SPECIES IN ORANGE COUNTY
Aegilops triuncialis - GOATGRASS Emergent Invasive
Aegilops triuncialis - GOATGRASS
Score: 1.00
Plant Profile
Known OC sites:
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Audubon Starr Ranch
Status Updates (from management in which OC CNPS is involved):
A first report for Orange County was located in May 2015 over about 8 square meters in a grassland area at Audubon Starr Ranch. The detection was made by Jordan Isken, a biologist at the ranch. Management began immediately, with hand removal. Surveys and ongoing management have been consistent by the staff and interns at the ranch. No additional plants were located in 2016.
The small population at Starr Ranch has been under aggressive surveying and management since its detection. Through 2022, no plants have been found during the past few years, but surveys will continue until there is certainty of the seed bank being exhausted.
Brassica fruticulosa - MEDITERRANEAN CABBAGE Emergent Invasive
Brassica fruticulosa - MEDITERRANEAN CABBAGE
Plant Profile
Score: 1.25
Known OC sites:
- Harriett Weider Park, Bolsa Chica Marsh
- Sully Miller Pond, Huntington Beach (unconfirmed)
The first OC detection was made by Jesse Potter (then of the Bolsa Chica Conservancy) on Mar 18, 2020. OCCNPS botanists visited the site, took a collection, and confirmed the identification. The colony is under management by the Bolsa Chica Conservancy; however identification is challenging due to it resemblance to other non-native Brassicaceae, which are abundant in the area.
Spread to the immediately adjacent private oil properties is suspected but not confirmed due to access limitations.
On public lands management continues to be aggressive by the Bolsa Chica Conservancy and OC Parks.
Centaurea benedicta - BLESSED THISTLE Emergent Invasive
Centaurea benedicta - BLESSED THISTLE
Score: 2.25
Plant Profile
Known OC sites:
- San Juan Creek, Casper Wilderness Park
A single plant was detected and photographed on May 31, 2020, by OCCNPS member Diane Etchison in the San Juan Creek drainage at Caspers Park. It was re-found by Bob Allen six weeks later and re-photographed. Additional plants have not been found, even after several surveys over the past two years. This may have been a waif and has not established.
Centaurea diluta - SPOTTED KNAPWEED Emergent Invasive
Centaurea diluta - SPOTTED KNAPWEED
Score: 1.50
Plant Profile
Known OC sites:
- Villa Park Dam.
- Irvine Open Space along I-5 Fwy., between Jeffrey and San Canyon Rd.
- Two locations in Fullerton, about 1 km apart.
Total Orange County infestation estimated: +-29 acres
To see a detailed list and map of all O.C. Calflora records, click HERE
To see additional photos from CalPhotos, click HERE
Status Update:
This species has been known at least from the early 1970's from the Villa Park Dam site, just West of Irvine Park. Originally it was misidentified as Centaurea stoebe, but was corrected by OCCNPS botanists in the 2010's. For the next 45 years the plant has persisted at the Villa Park site and expended within the basin, but had not moved beyond. Thus, its invasiveness was in doubt, at least locally.
However, this may be changing and there is speculation that this may be a "sleeper" species, one in which the species lies fairly dormant for several generations, then one of the phenotypes adapts rather quickly to local conditions. At that point, a population explosion begins.
In 2019 a fairly small population was detected and confirmed in Fullerton and two years later another was detected about a kilometer away. Meanwhile, in 2019 a large population was detected in Irvine along the margin of an open space reserve.
The Irvine population is being managed by the Irvine Ranch Conservancy in cooperation with the City of Irvine. As far as we know there is no management of the Fullerton or Villa Park colonies.
This species is one in which we are particularly interested in new detections.
Centaurea solstitialis - YELLOW STAR THISTLE Emergent Invasive
Centaurea solstitialis - YELLOW STAR THISTLE
Score: 2.25
Plant Profile
Known OC sites:
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Coal Canyon
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Gypsum Canyon
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San Juan Canyon, approx. nine or ten known colonies (some in Riv. Co.)
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Caspers Wilderness Park, along SR74
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Silverado Canyon: upper end past USFS gate
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South Main Divide Road (Riv. Co.):
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Elsinore Peak vicinity
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Meadow (potrero) just south of Rancho Capistrano
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Rancho Capistrano community
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Total Orange County infestation estimated: 10-15 acres
To see a detailed list and map of all O.C. Calflora records, click HERE
To see additional photos from CalPhotos, click HERE
Status Update:
Several separated colonies along the margins of SR74 (the Ortega Highway) have been managed thoroughly since at least 2012 by OCCNPS, with all found plants removed
Annual pull counts for these SR74 colonies:
2014: 11,309 plants 2016: 2,543 plants 2018: 310 plants 2020: 1,777 plants 2022: 358 plants
2015: 1,556 plants 2017: 1,716 plants 2019: 1,116 plants 2021: 38 plants 2023: ?
Management of all SR74 colonies have been under aggressive management by OCCNPS volunteers and will continue.
Count fluctuations vary, mostly due to new detections of colonies and likely from variations in rainfall, roadside grading, and disturbances. New colonies were detected and added to the management in 2021, 2016, and 2015. Plants are removed on or about July 4 or one to two weeks prior depending on rainfall and plant phenology each year. This aligns with bud break and early flowering, but prior to the plants entering a reproductive stage.
A somewhat smaller population in upper Silverado Canyon, comprised of scattered subcolonies over 1-2 miles is also being aggressively managed by OCCNPS volunteers since 2014. These plants are also hand pulled with the cooperation and permission of The Cleveland National Forest. Counts have fallen significantly from the high of 2,056 pulled in 2015.
Infestations continue in the Northern Santa Ana Mountain foothills, especially in the Coal Canyon area (CA State Parks). Some management has been performed on these colonies. A large, extended colony in Gypsum continues toward SR241 and crosses it onto Caltrans land on the West side of the Northern Toll Plaza. It is being successfully managed in these locations by the Irvine Ranch Conservancy.
Smaller, emergent populations in lower Silverado Canyon, Caspers Park, Aliso-Wood Canyon Park, and Irvine Regional Park are all under management.
Chrysanthemoides monilifera - BONESEED Emergent Invasive
Chrysanthemoides monilifera ssp. monilifera - BONESEED
Score: 2.25
Plant Profile
Known OC sites:
- Laguna Beach:
- Near the mouth of Aliso Creek, along the sea bluff North & up the canyon just past the water district building.
- Hortense Miller Garden, Laguna Beach
- Vic of Boat Canyon Trail, Laguna Coast Wilderness Park.
- Newport Beach:
- Along Pacific Coast Highway, just SE of Morning Canyon Road.
Status Update:
This species was detected by OCCNPS near the mouth of Aliso Creek in Laguna Beach in Feb, 2013. Subsequent surveys have documented this colony extending to the coastal strand. With the exception of an uncertain population at Palomar College in San Diego County, this was the first detection of the species in California. This colony has spread North, up the beachfront to Treasure Island Beach. This colony is now known from additional intermittent plants scattered throughout the urban landscapes and urban edges of the area of Aliso Creek to about .4 mi N.
Additional plants were found naturalized in urban HOA landscaping in Corona del Mar. These pants are all plants still extant. A few plants at the former UCI Arboretum were removed at the request of OCCNPS. Old plants located at the Hortense Miller Garden in Laguna Beach are concerning. At the request of OCCNPS some of these plants were removed, but others persist. Given the adventuresome spirit of this garden, there is suspicion that this may have been the point of introduction of the species to CA, with seed and plants possibly distributed elsewhere.
In 2022 numerous additional plants were located naturalizing behind housing in the Boat Canyon area of Laguna Beach. These plants are not being managed.
A 2016 report from upper Nyes Place at an urban edge location was confirmed negative. It is a related Chrysanthmoides rotundata, a species that is not known to be invasive.
Currently the infestation is spread across a very non-contiguous area of 8.5 miles
In March 2015, with the urging of OC CNPS, CA Dept. of Food and Agriculture gave this species an A Rating, the highest rating available for a pest plant. The complete listing can be viewed here.
Dipogon lignosus - OKIE BEAN Emergent Invasive
Score: 1.50
Plant Profile
Known OC sites:
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Mouth of Aliso Creek, Laguna Beach
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NE margin of Bolsa Chica Marsh, Huntington Beach
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Laguna Beach, four locations
Total Orange County infestation estimated: .5 acres.
Status Update:
This species was detected in wildlands for the first time in Orange County by James Bailey of OCCNPS near the mouth of Aliso Creek, in Laguna Beach on Aug. 14, 2020. This colony was visited by invasive plant management volunteers, led by Joan Miller, but the location of the colony was too dangerous for management. by that team. Management here has not yet begun, as far as we know.
In March and April of 2022 additional colonies were located in urban edge locations at three disjunct sites in Laguna Beach. These detections were made by Chris Gort of the Laguna Canyon Foundation. These colonies have all been field checked by OCCNPS. Most or all straddle private properties. No management is underway on these colonies.
A modest colony at an urban edge location at the Northern boundary of the Bolsa Chica Ecological Preserve was located in April, 2022. The colony appears to straddle private/public lands at a fenceline. The colony has been reported to land managers and biologist at the preserve. As far as we know, no management has begun.
Euphorbia terracina - GERALTON CARNATION WEED Emergent Invasive
Euphorbia terracina - GERALTON CARNATION WEED
Score: 1.50
Plant Profile
Known OC sites:
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O'Neill Regional Park
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Newport Peninsula, Newport Brach
Total Orange County infestation estimated: .1 acres
Status Update:
This highly invasive and disruptive species has been known for some time from just outside of OC. Plants grow within three miles of OC to the North in the Rowland Heights area. Additionally, a single plant was located in San Mateo Creek in San Clemente in 2020, within .4 km of Orange Co. at the Southern border.
On May 19, 2021, Johnny Iglesias, a biologist working at O'Neill Regional Park, detected a colony. It was field checked by OCCNPS, herbarium samples collected, delineated, and reported to OC Parks Natural Resources. The colony is over about 200 square meters of coastal sage scrub. Some management has begun, but the plants persist. This is a high priority and a point of infestation and potential spread.
Galenia pubescens - COASTAL GALENIA Emergent Invasive
Galenia pubescens - COASTAL GALENIA
Score: 2.00
Plant Profile
Known OC sites:
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Water Tank Trail (Bommer Ridge), Laguna Coast Wilderness Park
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Boat Canyon Trail, Laguna Coast Wilderness Park
Total Orange County infestation estimated: .1 acres mapped, plus unmapped acreage.
Status Update:
This species was first detected in Orange County on May 31, 2017, by OCCNPS member Jonathan Frank. Less than ten plants were detected in a very small patch off a trail variously called Water Tank Trail and Bommer Ridge Trail. The plants were removed and are checked regularly by OC Parks invasive plant volunteers led by Joan Miller. Plants were removed in 2018 and 2019 and none have been detected here since.
In May 2020, a larger colony was detected by OC Parks near the base of Boar Canyon Trail. This colony has number between 100-200 plants. It has been aggressively managed by OC Parks Invasive Plant volunteers since this time, with all plant being removed.
Hypericum canariense - CANARY ISLAND ST. JOHN'S WORT Emergent Invasive
Hypericum canariense - CANARY ISLAND ST. JOHN'S WORT
Score: 1.50
Plant Profile
Known OC sites:
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Dana Point:
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In Headlands Hilltop Conservation Park, above Street of the Green Lantern
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San Juan Capistrano: near La Novia Avenue & Valle Road, & on ridge above, 4.17 acres gross area.
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Laguna Canyon, from approx. opposite the Festival of the Arts to approx. Laguna College of Art & Design at Big Bend
Total Orange County infestation estimated: Discontinuous over up to 40+ acres
Status Update:
Since at least the 1970's a colony has been present in San Juan Capistrano (per Fred Roberts). During that period, the colony's margin has expanded, but it has not appeared to have moved to adjoining lands. Little if any management has taken place that this colony in the ensuing years. However, in 2021 a portion of the colony was removed, by coincidence, during a housing and commercial development.
An old colony near the Dana Point Headlands was aggressively managed during the 1990's-2,000's. Most of the plant were successfully removed. A few occasionally return and continue to be managed.
On May 18, 2017 a detection in Laguna Canyon was reported through this Emergent Invasive Program, by Dr. Peter Bryant. It was quickly field checked, roughly mapped and can be seen on Calflora (HERE). This is a significant infestation of a highly problematic plant. The colony was well established and spread over approximately one linear mile of the canyon side, primarily on the SE side. The Laguna Canyon Foundation, with support from the City of Laguna Beach quickly initiated aggressive management in 2018 and continues management currently, with a goal of eradication. A few plants on private property may be a challenge.
Melinis repens - NATAL GRASS Emergent Invasive
Melinis repens - NATAL GRASS or RUBY GRASS
Score: 1.50
Plant Profile
Known OC sites:
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Niguel Hill area in scattered locations, Laguna Niguel
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Santa Ana Canyon, at Gypsum Cyn. and +- .6 mi East
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Avenida San Pablo, San Clemente
Total Orange County infestation estimated: 4.61 acres mapped, plus unmapped acreage.
Status Update:
A single seeding plant was located and removed by OC CNPS along the Santa Ana River Bike Trail, 1 mile E of Gypsum Canyon Road. Area searched, but no others located. Record posted to Calflora.
Care should be taken not to confuse this species with the similar horticultural species, M. nerviglumis, which is not invasive.
Plants through the Niguel Hill area appear to be from hydroseed on HOA slopes, either intentionally or as a seed contaminant. The plant is now moving from these urban interface slopes into wildland locations. No management appears to be underway. These colonies are almost certainly the result of a hydroseed application in HOA urban edge landscaping.
Management is uncertain at the Gypsum Canyon and Santa Ana Canyon infestation, but is likely by the Irvine Ranch Conservancy.
Parthenium hysterophorus - SANTA MARIA FEVERFEW Emergent Invasive
Parthenium hysterophorus - SANTA MARIA FEVERFEW
Score: 1.00
Plant Profile
Known OC sites:
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Santa Ana, SE corner of Lincoln Ave and 17th Street
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Irvine, San Diego Creek channel, between Culver (Irvine) and Edinger Ave. (Tustin)
Total Orange County infestation estimated: .5+ acres.
Status Update:
In April, 2015, the first detection (and collection) in CA is made by a Jan West (specific identity is unknown) in urban Santa Ana.
In Aug, 2016, OCCNPS member Barbara Boethling detected a single plant in San Diego Creek Channel, adjacent to the San Joaquin Freshwater Marsh and Audubon offices. The plant is removed by OCCNPS and the surrounding area surveyed. No additional plants are found. Subsequent surveys continue over the next two years with 3-4 additional plants found and removed by OCCNPS. In July 2018 OCCNPS member Jonathan Frank discovers large population of up to 1,000 plants over a few acres approximately one mile further upstream. These plants were reported to OC Public Works, who begin management.
Management of this colony continues sporadically; however it has expanded considerably and now exists nearly two miles further up the channel.
Meanwhile, the Santa Ana colony is in a very urban location, adjacent to railroad tracks and urban landscaping. This colony was initially treated by OC Public Works in 2016, but with no subsequent management. Plants here have been managed several times by OCCNPS, but the population continues, although with no wildlands in the vicinity. This location may be the origins of the CA plants, as the species is occasionally used in homeopathic medicine by some cultures.
This species was given an A Rating by CDFA at the urging of OCCNPS, but management is very piecemeal and ineffective at present. These colonies persist as the point of entry and future establishment in CA for this very problematic invasive plant.
Rubus armeniacus - HIMALAYAN BLACKBERRY Emergent Invasive
Rubus armeniacus - HIMALAYAN BLACKBERRY
Score: 2.00
Plant Profile
Known OC sites:
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Chino Hills: unspecified location(s)
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Huntington Beach: Huntington Central Park
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Laguna Hills: at small pond southeast of Moulton Parkway & Ridge Route. 355 square meters gross area.
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San Juan Capistrano, El Horno Creek at Rancho Viejo Rd.
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Silverado Canyon:
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Hills above the road - nonspecific location
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Lower Silverado Canyon: Drainage on eastern edge of Irvine Ranch Open Space, west of Horse stables
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Upper Trabuco Canyon, nr. Falls Canyon
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Aliso Creek, nr. Aliso Niguel High School
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Park Avenue, Laguna Beach
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Santiago Canyon (=Modjeska Cyn.), near the Community Center
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Upper Newport Bay:
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Big Canyon, below apartments, on HOA/City of Newport Beach property
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Total Orange County infestation estimated: 2-4 acres.
To see a detailed list and map of all O.C. Calflora records, click HERE
To see additional photos from CalPhotos, click HERE
Status Update:
This highly problematic rambling vine is a major invasive in many parts of California and the west coast, but is still emergent in Orange County. Unfortunately, very little management is underway on these colonies, likely due to the challenges involved in management.
The well-established colony at Huntington Central Park received some good management between the years of approximately 2018-2021. Many plants were removed, but the colony is far from extirpated.
The Trabuco and Santiago Canyon colonies should be a priority for the US Forest Service, esp. the Trabuco colony given its location in an otherwise intact riparian community and its potential to spread in the watershed.
The Big Canyon colony at Upper Newport Bay should also be a priority given its adjacency to the sensitive Upper Newport Bay Preserve and the small colony size.
The Aliso-Wood Canyon and Park Avenue sites are assumed to be under management by the Laguna Canyon Foundation. And the Silverado Canyon colony is assumed to be under management by the Irvine Ranch Conservancy and/or OCTA.
The El Horno Creek and Laguna Hills colonies are under no management.
Senecio angustifolius Emergent Invasive
Score: 1.25
Plant Profile
Known OC sites:
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Agua Chinon Wash, Irvine (possibly extirpated)
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Harding Canyon, Cleveland National Forest, Santa Ana Mts.
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Red Rock Canyon, Whiting Ranch Wilderness Park
Total Orange County infestation estimated: .1 acres
Status Update:
This is a relatively new invasive in California, first recorded on Aug. 17, 2010, at Camp Pendleton, USMC where it has since spread. In Feb. 2016, Josie Bennett (then with the Irvine Ranch Conservancy) found a single plant in the Agua Chinon, East of Irvine. Then, on Nov. 18, 2018, another single plant was located in Harding Canyon by OCCNPS member Jonathan Frank. Shortly thereafter, on Nov. 25 a colony suspected also by Jonathan Frank, was confirmed in Red Rock Canyon, Whiting Ranch.
All colonies have been thoroughly surveyed by OCCNPS, the Irvine Ranch Conservancy and/or OC Parks for additional plants. The Agua Chinon area around the detection was checked again by OCCNPS and IRC, but no plants could be located. The single Harding Canyon plant was removed and no others have been located, even after several OCCNPS checks.
The plants in Red Rock Canyon are now the primary concern. This is a small colony with most plants over perhaps 100 sq. meters, but a few isolated in another pocket a km or so further up the canyon. OC Parks, with assistance from OCCNPS and volunteers have been aggressively managing this colony, with a goal of extirpation.
The CA Invasive Plant Council, with assistance from OCCNPS, is currently performing a scientific review of the invasive status of this species. Little is known currently of its biology and invasiveness, with this CA infestations appearing to be the first occurences outside of its native South Africa.
Senecio linearifolius var. linearifolius - LINEAR-LEAVED AUSTRALIAN FIREWEED Emergent Invasive
Senecio linearifolius var. linearifolius - LINEAR-LEAVED AUSTRALIAN FIREWEED
Score: 2.00
Plant Profile
Known OC sites:
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Irvine:
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Shady Canyon Drive & Bonita Canyon Road.
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Below the San Joaquin Reservoir, near Bonita Cyn. Dr. and Chambord
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University Drive & Culver Drive, in Mason Park
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Laguna Niguel/Dana Point:
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Esp. in the Salt Creeks corridor and along Pacific Island Drive, etc.
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Mission Viejo:
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Along a 2-3 mi. stretch of Oso Creek
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Total Orange County infestation estimated: 6+ acres, plus additional unmapped acreage.
To see a detailed list and map of all O.C. Calflora records, click HERE
To see additional photos from CalPhotos, click HERE
Status Update:
The first detection in California of this invasive plant was in a single plant in the Oso/Trabuco Creek area in 1985. Another was not found until 1998 in Irvine, near UCI. It is now firmly also established in San Diego County. Beginning in 2020 it has been reported in the San Francisco Bay area and as far North as Mendocino County.
In Orange County, the species is now well disturbed and expanding, esp. in the South OC areas of Laguna Niguel and Dana Point. The expanding colony along Pacific Island Drive in Laguna Niguel has had no management and those in the Salt Creek drainage have had very minimal management. The Irvine and Mission Viejo (Oso/Trabuco Creeks) are also not receiving any management.
This plant is expanding in Orange County and may soon be past an emergent stage.
Volutaria tubuliflora - EGYPTIAN KNAPWEED Emergent Invasive
Volutaria tubuliflora - EGYPTIAN KNAPWEED
Score: 2.00
Plant Profile
Known OC sites:
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Upper Newport Bay:
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Big Canyon area of Upper Newport Bay, Newport Beach.
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On the mesas along Irvine Blvd. on the West side of the bay.
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Total Orange County infestation estimated: 2-4 acres
To see a detailed list and map of all O.C. Calflora records, click HERE
To see additional photos from CalPhotos, click HERE
Status Update:
For an excellent discussion of this species in Southern California see the article by Frank Harris, Kate Harper, Tom Chester, and Ron Vanderhoff HERE.
For a brief article specific to the Orange County population, see the article by Ron Vanderhoff HERE.
In Orange County, this highly invasive species is known only from Upper Newport Bay. On March 31, 2014, OCCNPS member Barbara Boethling noticed an unusual plant in the Big Canyon area of Upper Newport Bay and sent photographs through this Invasive Plant Program to OCCNPS. The usual plant was identified as this species and within 24 hours the site was visited and additionally surveyed. In Jan. 2016 Dr. Peter Bryant located additional plants across the bay near the Muth Center/Irvine Blvd.
Both colonies have since been thoroughly surveyed and management has been rigorous, with partners including CDFW, OC Parks, City of Newport Beach, Newport Bay Conservancy, Irvine Ranch Conservancy, OCCNPS, Cal-IPC, the Natural Communities Coalition, UCCE, and others. This has been one of the most comprehensive and collaborative invasive plant efforts in OC. Annual management has been ongoing since the first detection, with numbers much reduced, from thousand to low hundreds. The Newport Bay Conservancy has become the lead agency for management.
During research on a related species OCCNPS made an important discovery about this species origins in California. OCCNPS discovered possible records dating to as early as 1987 at UNB. A photograph and comments of "Centaurea muricata" by Robert DeRuff (deceased) is made in The Vascular Plants of Upper Newport Bay.
A voucher specimen of the same record was deposited at the UC Riverside herbarium, also under the name Centaurea muricata. We now know that these records refer to Volutaria tubuliflora. In the records Mr. DeRuff mentions both Big Canyon and the bluffs not far from the Muth Center, both locations of our 2015 and 2016 records.
The specimen at UCR was confirmed V. tubuliflora and moves the date of California introduction forward by at least several years and also changes the introduction point from Borrego Springs to Newport Beach.
FORMER EMERGENT SPECIES
These species were previously Emergent Invasive in Orange County. They are no longer rated Emergent, but are still significant detection and management concerns. New detections should be documented on Calflora and/or iNaturalist.
Araujia sericifera - BLADDERFLOWER Former Emergent 2016
FORMER EMERGENT SPECIES
Araujia sericifera - BLADDERFLOWER
?
Score: 2.75
Plant Profile
See all Orange County Calflora records HERE
To see additional photos from CalPhotos, click HERE
Orange County Status:
Now present through much of the lowlands of Orange County. Formerly a weed of citrus and tree crops, the vining perennial is now relatively common in loosely maintained urban landscaping. In wildlands it primarily occurs on the urban edge, especially in moist riparian habitats.
Asphodelus fistulosus - ONIONWEED Former Emergent 2016
FORMER EMERGENT SPECIES
?
Asphodelus fistulosus - ONIONWEED
?
Score: 2.25
Plant Profile
See all Orange County Calflora records HERE
To see additional photos from CalPhotos, click HERE
Orange County Status:
This species is now well past the Emergent stage in Orange County. It is especially present in urban edge environments and along adjacent gentle slopes and washes. Primarily known from foothill and coastal locations. Likely introduced either intentionally or as a seed contaminant is seed mixes applies to urban slopes it has now established widely. A difficult plant to manage, as the entire root system must be removed. Many herbicides are also only marginally effective.
Of special concern are plants or colonies beyond the urban edge and encroaching on wildlands communities.
Brassica tournefortii - SAHARA MUSTARD Former Emergent 2016-2017
FORMER EMERGENT SPECIES
Brassica tournefortii - SAHARA MUSTARD
Score: 2.50
Plant Profile
See all Orange County Calflora records HERE
To see additional photos from CalPhotos, click HERE
Orange County Status:
This very aggressive annual mustard has quickly invaded Orange County as well as most of the Southern half of California. Its environmental plasticity is especially challenging, as it appears to be nearly as happy in coastal habitats as it is in the dry interior deserts. A prolific producer of seed along with its very early germination add to its abundance.
Its first report in Orange County was as recent as 1986, with the next not until 2003. Since then it has spread quickly. Initially primarily known in California from the western deserts it then moved to the inland valleys of Southern California. It then leaked into Orange County primarily via Santa Ana Canyon, but invariably was spread into the county via seed from other sources as well (equipment, clothing, animals, etc.).
It is especially suited to sandy, disturbed soils and often initiates infestations along trailsides, sandy wash margins, orchard edges and ruderal areas, but then moves into more intact plant communities.
Management continues in many areas of Orange County, especially high value locations. Examples of these still somewhat isolated infestations are at Caspers Park and portions of the San Joaquin Hills (Laguna Coast, etc.), where it is still likely emergent.
Detections of this species should continue to be reported and mapped on Calflora and/or iNaturalist.
Delairea odorata - CAPE IVY Former Emergent 2016-2019
FORMER EMERGENT SPECIES
Score: 2.25
Plant Profile
See all Orange County Calflora records HERE
To see additional photos from CalPhotos, click HERE
Orange County Status:
In wildlands, this is an environmental weed primarily of moist canyon bottoms, riparian communities and shaded brushy oak woodlands. The plant is also occasional in loosely maintained urban landscapes, where it rambles along the ground or climbs through and over other plants.
In Orange County it seems to be especially prevalant in the Laguna Beach area, but also with plants in the mountain foothill canyons. Plants and colonies are generally near urban areas, canyon homes, cabins, etc.
Management is especially difficult because of its twining, overtopping habit, usually intermixed with native plants. Also its propensity to re-root at nodes that come into contact with soil.
Of special significance for management are those colonies that are away from urban areas and growing in otherwise healthy environments, or adjacent to them. Examples include Emerald Canyon (Laguna Beach), Hot Springs Canyon, Silverado Canyon, Modjeska (=Santiago) Canyon, and near the mouth of San Mateo Creek (San Diego Co.).
New wildlands detections should be reported.
Dittrichia graveolens - STINKWORT Former Emergent 2016-2020
FORMER EMERGENT SPECIES
Dittrichia graveolens - STINKWORT 
Score: 2.50
Plant Profile
See all Orange County Calflora records HERE
To see additional photos from CalPhotos, click HERE
Orange County Status:
The first California record of this highly problematic species was in the San Francisco area in 1984. It arrived in Orange County in 2011 with a detection by a member of the OCCNPS Invasive Committee in the Arroyo Trabuco area of O'Neill Regional Park. For a few years it was considered an Emergent Invasive species in Orange County. However, it has increased in occurrences and distribution to a level that no longer qualifies as Emergent.
Its current distribution is Orange County extends to several watersheds, both in mountain foothills as well all the way to the immediate coast. However, there are still many areas of the county where it has not been reported, especially the Northern portions. Any detections at new locations should be recorded and reported.
Often very aggressive management for the first few years of infestation, management has since relaxed somewhat. Land managers have varied responses to infestations. High value lands should continue to be protected from this very aggressive invasive plant.
Ehrharta calycina - PERENNIAL VELDT GRASS Former Emergent 2016-2020
FORMER EMERGENT SPECIES
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Ehrharta calycina - PERENNIAL VELDT GRASS
Score: 1.25
Plant Profile
See all Orange County Calflora records HERE
To see additional photos from CalPhotos, click HERE
Orange County Status:
This species of the San Joaquin Hills has been a management target of Orange County's Natural Communities Coalition for many years (NCP/HCCP).
During its tenure in Orange County, this plant was thought to be reasonably well contained on a few hillsides, ridges, and slopes of coastal sage scrub/grasslands in the central San Joaquin Hills. However, in the late 2010's, James Bailey conducted invasive plant surveys throughout the area and expanded the range and number of plants considerably. At that point, the species was removed from the OCCNPS Emergent list.
Perennial Veldt Grass continues to be managed in the San Joaquin Hills, but no longer with an expectation of extirpation.
Because occurrences of this plant are still limited to portions of the San Joaquin Hills, any detections in other areas of the county should immediately be recorded on Calflora and/or iNaturalist. Identification can be problematic; please include very close-up images of the flowers (spikelets).
Emex spinosa - SPINY EMEX Former Emergent 2016-2017
FORMER EMERGENT SPECIES
Score: 2.50
Plant Profile
See all Orange County Calflora records HERE
To see additional photos from CalPhotos, click HERE
Orange County Status:
Spiny emex has been in Orange County for over 90 years, but occurred sporadically and was an insignificant environmental pest. However, beginning in the early 2010's the plant began spreading aggressively in the county, and elsewhere in Southern California. Only eight records prior to 2010 have exploded to nearly 300 since then. Is this an example of a "sleeper" population?
"Sleepers" are plants that persist in small numbers for years or decades, then with a change in an unknown environmental factor or an adaptive selection, become highly abundant and disruptive.
Currently spiney emex is well distributed and expanding in the almost all parts of the county, from the immediate coastal strand to the foothills, and often in dense stands.
Management was aggressive in the 2010's when the plant began expanding its distribution but today is irregular.
Iris pseudacorus - YELLOW FLAG IRIS Former Emergent 2016-2017
FORMER EMERGENT SPECIES
Iris pseudacorus - YELLOW FLAG IRIS(Mobile).JPG?i=294)
Score: 3.00
Plant Profile
See all Orange County Calflora records HERE
To see additional photos from CalPhotos, click HERE
This is a semi-aquatic plant always occurring either in standing water or immediately adjacent. It is also a plant of urban ponds and aquatic gardens.
In Orange County the primary wildlands infestation is in Laguna Canyon/Laguna Creek from near Lake Forest Drive to just South of the Marine Mammal Center, where the soft bodies creek is replaced by a concrete culvert. Infestations along this corridor can be quite common.
Elsewhere in Orange County isolated colonies are found at widely scattered locations. Caution should be taken by pond gardeners with this species as the seed and rhizomes are a threat to freshwater wetland communities, such as at the Laguna Lakes. Once in a drainage corridor the rhizomes are easily dislodged and moved downstream to re-root and enlarge the colony, resulting in hydrologic issues as well as loss of habitat.
All new infestations should be reported on Calflora and/or iNaturalist.
Lepidium draba - WHITETOP Former Emergent 2016
FORMER EMERGENT SPECIES
Score: 2.50
Plant Profile
See all Orange County Calflora records HERE
To see additional photos from CalPhotos, click HERE
Orange County Status:
Whitetop occurs in widely scattered locations through the lowland's areas of Orange County. In Orange County it has not spread prolifically, despite being present for over 100 years.
Populations generally occur in moist, disturbed sites, such as weedy fields, margins of roadways and other disturbed sites. Where is does occur its abundance seems to vary considerably, probably as a result of rainfall fluctuations.
Management is uncertain, but probably best reserved for high priority locations.
Lepidium latifolium - BROAD-LEAVED PEPPERGRASS Former Emergent 2016-2017
FORMER EMERGENT SPECIES
Lepidium latifolium - BROAD-LEAVED PEPPERGRASS
Score: 2.50
Plant Profile
See all Orange County Calflora records HERE
To see additional photos from CalPhotos, click HERE
Orange County Status:
One of the more troublesome invasive plants of freshwater and brackish water habitats. Although well distributed elsewhere in California, it has only expanded significantly in Orange County in the past twenty or so years. It is now present in many lowland freshwater habitats. Due to its rhizomatous nature and habit of intermixing with native riparian vegetation it is quite difficult to manage successfully. It spreads and infest from both seed dispersal, rhizomes and vegetative pieces that are dispersed by water.
If it is found in a new, unrecorded watershed or location it is important that it be reported promptly. Management success is improved significantly if the population is small.
Ludwigia hexapetala - CREEPING WATER PRIMROSE Former Emergent 2016
FORMER EMERGENT SPECIES
Ludwigia hexapetala - CREEPING WATER PRIMROSE
?
Score:
Plant Profile
See all Orange County Calflora records HERE
To see additional photos from CalPhotos, click HERE
Orange County Status:
Ludwigia species can be difficult to locate and even more difficult to identify correctly. These are aquatic plants that generally require free water, often making their approach challenging. Further, the species can be rather cryptic and somewhat challenging to separate
This species is similar in appearance to the much more common Ludwigia peploides, which was for many years presumed to be native, but now assigned as a non-native invasive plant as well. L. hexapetala had sepal bases which are deltate (wide and flattened at the point of attachment), while L. peploides are lanceolate (narrow and tapering to the base).
L. hexapetala was known from Orange County by a single 2004 collection at Upper Newport Bay. However, no subsequent records have been made and surveys of the collection area have also been negative. Therefore that species has been removed from the Emergent Invasive list.
Nonetheless, this species does occur in Coastal Southern California and is also an occasional pond garden plant. Because of its difficulty in detection and identification it could be present in the county. Therefore, colonies of Ludwigia should be periodically examined carefully for this species and reported promptly if found.
Oncosiphon piluliferum - STINKNET Former Emergent 2016-2019
FORMER EMERGENT SPECIES
Oncosiphon piluliferum - STINKNET.jpg?i=780)
Score: 2.75
Plant Profile
See all Orange County Calflora records HERE
To see additional photos from CalPhotos, click HERE
An invasive plant that has exploded in abundance in Southern California and Orange County and is causing significant environmental damage. California's first detection was in the Perris Valley in 1981 and Orange County's first report was in 2003 at the former El Toro Marine Base, where it quickly became abundant.
In the ensuing years in Orange County, the plant has spread to nearly all parts of the county, from the immediate coast to the high Santa Ana Mountains. It's ability to invade a wide variety of habitats and climatic extremes is especially concerning. Stinknet was especially noticeable in the Santa Ana Mountains during OCCNPS post-fire surveys following the 2018 Santiago Fire. This was one of the first plants to re-appear in the charred, barren soil, probably arriving from wind-blown seed coming in from the Elsinore Valley, where it is quite common.
Because of its current abundance, combined with often limited management resources, its control is irregular. High priority habitats and those not yet infested likely receive the most management. This is currently one of the most problematic invasive plants in Southern California.
Robinia pseudoacacia - BLACK LOCUST Former Emergent 2016
FORMER EMERGENT SPECIES
Robinia pseudoacacia - BLACK LOCUST
?
Score: 3.50
Plant Profile
See all Orange County Calflora records HERE
To see additional photos from CalPhotos, click HERE
Plants and small to moderate colonies are scattered throughout Orange County from near the coast to the Santa Ana Mountains. Most occurrences are near abandoned houses, roadsides, and waste areas, but also naturalizes in riparian corridors and adjacent mesic slopes. The plant is too abundant in Orange County to be considered Emergent.
An occasional tree of urban landscapes, but usually disliked due to its size, messiness, and propensity to sucker and seed. The tree spreads both through abundant seed as well as vegetatively from rhizomes and can be difficult to remove or kill, often returning from suckers.
Seeds, leaves, and bark are all toxic and can even be fatal if ingested by humans or livestock.
Detections in new wildland locations, especially moist canyons of native vegetation should be recorded on Calflora or iNaturalist. Isolated plants adjacent to habitat should be carefully removed, including all root remnants, then monitored for a few years for re-sprouts or seedlings.
Salpichroa origanifolia - LILY-OF-THE-VALLEY-VINE Former Emergent 2016
FORMER EMERGENT SPECIES
Salpichroa origanifolia - LILY-OF-THE-VALLEY VINE
?
Score: 2.00
Plant Profile
See all Orange County Calflora records HERE
To see additional photos from CalPhotos, click HERE
Orange County Status:
This species is no longer emergent based primarily upon its low levels of environmental disruption and propensity to be always adjacent to urban habitation.
Several colonies have recently been detected by the Laguna Canyon Foundation in the Laguna Beach area, including Laguna Canyon and especially the vicinity of Mission Hospital in South Laguna. Other detections are scattered.
A small colony at Crystal Cove State Park, present for several years, was reported by OCCNPS and treated by park staff in 2013, but has reappeared. A check of the site by OCCNPS revealed that plants have returned at the area near the day parking area at the El Moro entrance.
A single colonial clump was located by OC CNPS along the roadside in Hot Springs Canyon. The plants were removed, but some rhizomes were unable to be excavated. The location is being monitored for additional plants.
Any new detections, especially in wildlands locations, should be reported.
SPECIES REVIEWED BUT REJECTED
These species have been carefully reviewed for consideration as an Emergent Invasive Plant in Orange County, but have been rejected. They will continue to be assessed annually. A rejection may be for various reasons:
- Their distribution and abundance in the county have expanded past the Emergent level.
- Although naturalized in the county, the species has not proven significantly invasive, and causing environmental disruption.
- The occurrence(s) in the county are likely waifs and they have not been determined as persisting, naturalizing and being invasive.
- The species is primarily aquatic.
|
Botanical Name |
Common Name |
Date Added |
Score |
|---|---|---|---|
| Ageratina adenophora | STICKY SNAKEROOT | 2017 | 3.50 |
| Now well distributed in moist shaded drainages, coast to mountains. | |||
| Albizia lophantha | STINK BEAN | 2020 | 3.50 |
| Widely scattered locations. Ecological impacts appear to be low. | |||
| Commelina benghalensis | DAYFLOWER | 2018 | 3.50 |
| Often seen in weedy urban areas, But not significant or established in native vegetation. | |||
| Crassula colligata ssp. colligata | AUSTRALIAN PYGMYWEED | 2021 | 2.50 |
| First OC record in 2020. Environmental impacts not proven. | |||
| Dinebra retroflexa | VIPER GRASS | 2022 | 2.50 |
| A very small first OC detection in Irvine in 2021. Managed by OCCNPS and not re-found in future surveys. Waif status for now. | |||
| Elymus ponticus | TALL WHEAT GRASS | 2021 | 1.50 |
| A single mature plant detected and removed in 2020 in Aliso-Wood Canyon Wilderness Park. Monitoring. | |||
| Erodium malacoides | MEDITERRANEAN FILEREE | 2018 | 2.75 |
| A handful of scatterred detections since 2016. Species is being monitored for environmental impacts. | |||
| Euphorbia segetalis | GRAINFIELD SPURGE | 2020 | 1.50 |
| A 1st OC confirmation in 2019 (nr. Trabuco Canyon) and another in 2022 (South Laguna). Being monitored. | |||
| Genista monspessulana | FRENCH BROOM | 2020 | 1.00 |
| A small population near cabins in Holy Jim Canyon is partially managed, but continuing. Monitoring for invasiveness. | |||
| Geranium molle | CRANE'S BILL GERANIUM | 2020 | 2.75 |
| Three OC observations, but not appearing invasive. More problematic to the North. | |||
| Geranium robertianum | ROBERT'S GERANIUM | 2020 | 2.75 |
| Apparently established at the Fullerton Arboretum, but nowhere else in the county. | |||
| Geranium rotundifolium | ROUND LEAVED GERANIUM | 2020 | 2.75 |
| A few records in urban edges dating to 2017, but not established in wildlands. | |||
| Ipomoea cairica | MILE-A-MINUTE VINE | 2017 | 3.00 |
| Well established at several coastal locations, esp. along the South Coast and mostly in urban edge landscaping. Past Emergent. | |||
| Lathyrus tingitanus | TANGIER PEA | 2021 | 1.50 |
| Several colonies along SR74, in Riv. Co. A possible detection in Caspers Park and one confirmed in Silverado Cyn, both 2022. Being monitored. | |||
| Leucaena leucocephala | WHITE LEADTREE | 2020 | 3.00 |
| A significant invasive elsewhere. Here, primarily in riparian communities. Being monitored. | |||
| Limonium duriusculum | SEA LAVENDER | 2016 | 3.50 |
| Well distributed in the county and now well past the Emergent stage. | |||
| Limonium otolepis | ASIAN SEA LAVENDER | 2016 | 3.00 |
| A small clump rediscovered in 2021, following an old 1997 record. Managed immediately. Establishment uncertain. | |||
| Limonium preauxii | SEA LAVENDER | 2016 | 3.00 |
| Old records for Upper Newport Bay. Not relocated. Needs confirmation. | |||
| Limonium sventenii | SEA LAVENDER | 2016 | 3.00 |
| A 2008 record for Lake Forest. Not relocated. Needs confirmation of an extant population. | |||
| Liquidambar styraciflua | SWEETGUM | 2017 | 3.00 |
| Occasional waifs, but not confirmed as an environmental threat. | |||
| Pallenis maritima | GOLD COIN | 2022 | 3.00 |
| Small patches are established at scatterred locations on ocean-facing bluffs, but not determined as having environmental impacts. | |||
| Parietaria judaica | SPREADING PELLITORY | 2021 | 2.75 |
| A recent urban weed primarily in the Huntington and Sunset Beach areas. Not yet detected in wildlands. | |||
| Parthenocissus inserta | WOODBINE | 2021 | 3.00 |
| Silverado and Irvine colonies are being monitored. | |||
| Paspalum vaginatum | SEASHORE PASPALUM | 2017 | 2.25 |
| A significant invasive, but now well established at many freshwater/brackish water locations. | |||
| Pelargonium grossularioides | GOOSEBERRY PELARGONIUM | 2021 | 3.00 |
| Scatterred plants and small colonies, but it's ability to invade wildlands is not established, nor its environmental impacts. | |||
| Pennisetum villosum | FEATHERTOP | 2017 | 2.50 |
| Scatterred around the county, but not proven strongly aggressive or disruptive. | |||
| Phytolacca americana | AMERICAN POKEWEED | 2021 | 3.25 |
| A few recent records (>2019) but at ruderal urban areas. Not appearing as a wildland's invader. | |||
| Phytolacca icosandra | TROPICAL POKEWEED | 2021 | 2.50 |
| Also a few records >2017, but all in urban areas or ruderal waste areas. Not establishing in wildland's. | |||
| Pistia stratiotes (aquatic) | WATER LETTUCE | 2018 | 1.50 |
| Aquatic plants are not included in the final OCCNPS Emergent Invasive Plant List. | |||
| Plantago arenaria | INDIAN PLANTAIN | 2017 | 2.00 |
| Common at the Bolsa Chica Ecological and other coastal wetlands. Past the Emergent stage. | |||
| Plecostachys serpyllifolia | PETITE LICORICE | 2017 | 2.25 |
| Occasional patches along coastal bluffs and coastal canyons. Monitoring. | |||
| Ranunculus arvensis | FIELD BUTTERCUP | 2017 | 2.50 |
| Two collections from 2000 have not been re-observed. Assumed extirpated. | |||
| Ranunculus muricatus | BUTTERCUP | 2021 | 2.75 |
| Two small patches in urban, irrigated landscaping only. | |||
| Rapistrum ragosum | TURNIPWEED | 2021 | 1.00 |
| Ladd Cyn (2019) and Upper Newport Bay (2020) detections. Monitoring. | |||
| Salvinia minima (aquatic) | WATER SPANGLES | 2021 | 1.00 |
| Aquatic plants are not included in the final OCCNPS Emergent Invasive Plant List. | |||
| Salvinia molesta (aquatic) | KARIBA WEED | 2017 | 1.00 |
| Aquatic plants are not included in the final OCCPS Emergent Invasive Plant List. | |||
| Senna didymobotrya | AFRICAN WILD CASSIA | 2017 | 2.25 |
| Plants and small colonies are scatterred through the lowlands. Not yet determined as a wildland invasive and likely past Emergent. | |||
| Sesbania punicea | RATTLEBOX | 2021 | 1.25 |
| A single plant was rediscovered and removed at Upper Newport Bay in 2020, following a 2006 detection. Waifs, not considered established. | |||
| Solanum aviculare (laciniatum?) | NEW ZEALAND NIGHTSHADE | 2017 | 2.50 |
| Taxonomy is confused, may be conspecific. A colony persists in Hunt. Central Park, but invasiveness is not certain. | |||
| Tamarix aphylla | ATHEL TAMARISK | 2021 | 2.75 |
| Small colonies in Black Star Cyn. and near Rancho Santa Margarita are concerning. Monitoring. | |||
| Triadica sebifera | CHINESE TALLOWTREE | 2017 | 1.50 |
| Populations, esp. in San Clemente and Orange are being monitored. Not in wildlands. | |||
.
Select an invasive species from the list below to see the locations of known Orange County occurrences, as well as a status update from the chapter. Please do not report known Orange County occurrences. However, all new occurrences of these species should be documented and mapped to either Calflora (preferred) or iNaturalist. Alternatively, you may report these to using the instructions at Reporting an Invasive Plant.
Status updates include information on new occurrences, management activities, updates about the population, successes and failures and other news regarding each invasive species. If you have other updates or corrections, please report them for inclusion to .
For occasional brief summaries of recent invasive plant information also see Invasive Updates.
2022 EMERGENT INVASIVE PLANT SPECIES IN ORANGE COUNTY
Aegilops triuncialis - GOATGRASS Emergent Invasive
Aegilops triuncialis - GOATGRASS
Score: 1.00
Plant Profile
Known OC sites:
-
Audubon Starr Ranch
Status Updates (from management in which OC CNPS is involved):
A first report for Orange County was located in May 2015 over about 8 square meters in a grassland area at Audubon Starr Ranch. The detection was made by Jordan Isken, a biologist at the ranch. Management began immediately, with hand removal. Surveys and ongoing management have been consistent by the staff and interns at the ranch. No additional plants were located in 2016.
The small population at Starr Ranch has been under aggressive surveying and management since its detection. Through 2022, no plants have been found during the past few years, but surveys will continue until there is certainty of the seed bank being exhausted.
Brassica fruticulosa - MEDITERRANEAN CABBAGE Emergent Invasive
Brassica fruticulosa - MEDITERRANEAN CABBAGE
Plant Profile
Score: 1.25
Known OC sites:
- Harriett Weider Park, Bolsa Chica Marsh
- Sully Miller Pond, Huntington Beach (unconfirmed)
The first OC detection was made by Jesse Potter (then of the Bolsa Chica Conservancy) on Mar 18, 2020. OCCNPS botanists visited the site, took a collection, and confirmed the identification. The colony is under management by the Bolsa Chica Conservancy; however identification is challenging due to it resemblance to other non-native Brassicaceae, which are abundant in the area.
Spread to the immediately adjacent private oil properties is suspected but not confirmed due to access limitations.
On public lands management continues to be aggressive by the Bolsa Chica Conservancy and OC Parks.
Centaurea benedicta - BLESSED THISTLE Emergent Invasive
Centaurea benedicta - BLESSED THISTLE
Score: 2.25
Plant Profile
Known OC sites:
- San Juan Creek, Casper Wilderness Park
A single plant was detected and photographed on May 31, 2020, by OCCNPS member Diane Etchison in the San Juan Creek drainage at Caspers Park. It was re-found by Bob Allen six weeks later and re-photographed. Additional plants have not been found, even after several surveys over the past two years. This may have been a waif and has not established.
Centaurea diluta - SPOTTED KNAPWEED Emergent Invasive
Centaurea diluta - SPOTTED KNAPWEED
Score: 1.50
Plant Profile
Known OC sites:
- Villa Park Dam.
- Irvine Open Space along I-5 Fwy., between Jeffrey and San Canyon Rd.
- Two locations in Fullerton, about 1 km apart.
Total Orange County infestation estimated: +-29 acres
To see a detailed list and map of all O.C. Calflora records, click HERE
To see additional photos from CalPhotos, click HERE
Status Update:
This species has been known at least from the early 1970's from the Villa Park Dam site, just West of Irvine Park. Originally it was misidentified as Centaurea stoebe, but was corrected by OCCNPS botanists in the 2010's. For the next 45 years the plant has persisted at the Villa Park site and expended within the basin, but had not moved beyond. Thus, its invasiveness was in doubt, at least locally.
However, this may be changing and there is speculation that this may be a "sleeper" species, one in which the species lies fairly dormant for several generations, then one of the phenotypes adapts rather quickly to local conditions. At that point, a population explosion begins.
In 2019 a fairly small population was detected and confirmed in Fullerton and two years later another was detected about a kilometer away. Meanwhile, in 2019 a large population was detected in Irvine along the margin of an open space reserve.
The Irvine population is being managed by the Irvine Ranch Conservancy in cooperation with the City of Irvine. As far as we know there is no management of the Fullerton or Villa Park colonies.
This species is one in which we are particularly interested in new detections.
Centaurea solstitialis - YELLOW STAR THISTLE Emergent Invasive
Centaurea solstitialis - YELLOW STAR THISTLE
Score: 2.25
Plant Profile
Known OC sites:
-
Coal Canyon
-
Gypsum Canyon
-
San Juan Canyon, approx. nine or ten known colonies (some in Riv. Co.)
-
Caspers Wilderness Park, along SR74
-
Silverado Canyon: upper end past USFS gate
-
South Main Divide Road (Riv. Co.):
-
Elsinore Peak vicinity
-
Meadow (potrero) just south of Rancho Capistrano
-
Rancho Capistrano community
-
Total Orange County infestation estimated: 10-15 acres
To see a detailed list and map of all O.C. Calflora records, click HERE
To see additional photos from CalPhotos, click HERE
Status Update:
Several separated colonies along the margins of SR74 (the Ortega Highway) have been managed thoroughly since at least 2012 by OCCNPS, with all found plants removed
Annual pull counts for these SR74 colonies:
2014: 11,309 plants 2016: 2,543 plants 2018: 310 plants 2020: 1,777 plants 2022: 358 plants
2015: 1,556 plants 2017: 1,716 plants 2019: 1,116 plants 2021: 38 plants 2023: ?
Management of all SR74 colonies have been under aggressive management by OCCNPS volunteers and will continue.
Count fluctuations vary, mostly due to new detections of colonies and likely from variations in rainfall, roadside grading, and disturbances. New colonies were detected and added to the management in 2021, 2016, and 2015. Plants are removed on or about July 4 or one to two weeks prior depending on rainfall and plant phenology each year. This aligns with bud break and early flowering, but prior to the plants entering a reproductive stage.
A somewhat smaller population in upper Silverado Canyon, comprised of scattered subcolonies over 1-2 miles is also being aggressively managed by OCCNPS volunteers since 2014. These plants are also hand pulled with the cooperation and permission of The Cleveland National Forest. Counts have fallen significantly from the high of 2,056 pulled in 2015.
Infestations continue in the Northern Santa Ana Mountain foothills, especially in the Coal Canyon area (CA State Parks). Some management has been performed on these colonies. A large, extended colony in Gypsum continues toward SR241 and crosses it onto Caltrans land on the West side of the Northern Toll Plaza. It is being successfully managed in these locations by the Irvine Ranch Conservancy.
Smaller, emergent populations in lower Silverado Canyon, Caspers Park, Aliso-Wood Canyon Park, and Irvine Regional Park are all under management.
Chrysanthemoides monilifera - BONESEED Emergent Invasive
Chrysanthemoides monilifera ssp. monilifera - BONESEED
Score: 2.25
Plant Profile
Known OC sites:
- Laguna Beach:
- Near the mouth of Aliso Creek, along the sea bluff North & up the canyon just past the water district building.
- Hortense Miller Garden, Laguna Beach
- Vic of Boat Canyon Trail, Laguna Coast Wilderness Park.
- Newport Beach:
- Along Pacific Coast Highway, just SE of Morning Canyon Road.
Status Update:
This species was detected by OCCNPS near the mouth of Aliso Creek in Laguna Beach in Feb, 2013. Subsequent surveys have documented this colony extending to the coastal strand. With the exception of an uncertain population at Palomar College in San Diego County, this was the first detection of the species in California. This colony has spread North, up the beachfront to Treasure Island Beach. This colony is now known from additional intermittent plants scattered throughout the urban landscapes and urban edges of the area of Aliso Creek to about .4 mi N.
Additional plants were found naturalized in urban HOA landscaping in Corona del Mar. These pants are all plants still extant. A few plants at the former UCI Arboretum were removed at the request of OCCNPS. Old plants located at the Hortense Miller Garden in Laguna Beach are concerning. At the request of OCCNPS some of these plants were removed, but others persist. Given the adventuresome spirit of this garden, there is suspicion that this may have been the point of introduction of the species to CA, with seed and plants possibly distributed elsewhere.
In 2022 numerous additional plants were located naturalizing behind housing in the Boat Canyon area of Laguna Beach. These plants are not being managed.
A 2016 report from upper Nyes Place at an urban edge location was confirmed negative. It is a related Chrysanthmoides rotundata, a species that is not known to be invasive.
Currently the infestation is spread across a very non-contiguous area of 8.5 miles
In March 2015, with the urging of OC CNPS, CA Dept. of Food and Agriculture gave this species an A Rating, the highest rating available for a pest plant. The complete listing can be viewed here.
Dipogon lignosus - OKIE BEAN Emergent Invasive
Score: 1.50
Plant Profile
Known OC sites:
-
Mouth of Aliso Creek, Laguna Beach
-
NE margin of Bolsa Chica Marsh, Huntington Beach
-
Laguna Beach, four locations
Total Orange County infestation estimated: .5 acres.
Status Update:
This species was detected in wildlands for the first time in Orange County by James Bailey of OCCNPS near the mouth of Aliso Creek, in Laguna Beach on Aug. 14, 2020. This colony was visited by invasive plant management volunteers, led by Joan Miller, but the location of the colony was too dangerous for management. by that team. Management here has not yet begun, as far as we know.
In March and April of 2022 additional colonies were located in urban edge locations at three disjunct sites in Laguna Beach. These detections were made by Chris Gort of the Laguna Canyon Foundation. These colonies have all been field checked by OCCNPS. Most or all straddle private properties. No management is underway on these colonies.
A modest colony at an urban edge location at the Northern boundary of the Bolsa Chica Ecological Preserve was located in April, 2022. The colony appears to straddle private/public lands at a fenceline. The colony has been reported to land managers and biologist at the preserve. As far as we know, no management has begun.
Euphorbia terracina - GERALTON CARNATION WEED Emergent Invasive
Euphorbia terracina - GERALTON CARNATION WEED
Score: 1.50
Plant Profile
Known OC sites:
-
O'Neill Regional Park
-
Newport Peninsula, Newport Brach
Total Orange County infestation estimated: .1 acres
Status Update:
This highly invasive and disruptive species has been known for some time from just outside of OC. Plants grow within three miles of OC to the North in the Rowland Heights area. Additionally, a single plant was located in San Mateo Creek in San Clemente in 2020, within .4 km of Orange Co. at the Southern border.
On May 19, 2021, Johnny Iglesias, a biologist working at O'Neill Regional Park, detected a colony. It was field checked by OCCNPS, herbarium samples collected, delineated, and reported to OC Parks Natural Resources. The colony is over about 200 square meters of coastal sage scrub. Some management has begun, but the plants persist. This is a high priority and a point of infestation and potential spread.
Galenia pubescens - COASTAL GALENIA Emergent Invasive
Galenia pubescens - COASTAL GALENIA
Score: 2.00
Plant Profile
Known OC sites:
-
Water Tank Trail (Bommer Ridge), Laguna Coast Wilderness Park
-
Boat Canyon Trail, Laguna Coast Wilderness Park
Total Orange County infestation estimated: .1 acres mapped, plus unmapped acreage.
Status Update:
This species was first detected in Orange County on May 31, 2017, by OCCNPS member Jonathan Frank. Less than ten plants were detected in a very small patch off a trail variously called Water Tank Trail and Bommer Ridge Trail. The plants were removed and are checked regularly by OC Parks invasive plant volunteers led by Joan Miller. Plants were removed in 2018 and 2019 and none have been detected here since.
In May 2020, a larger colony was detected by OC Parks near the base of Boar Canyon Trail. This colony has number between 100-200 plants. It has been aggressively managed by OC Parks Invasive Plant volunteers since this time, with all plant being removed.
Hypericum canariense - CANARY ISLAND ST. JOHN'S WORT Emergent Invasive
Hypericum canariense - CANARY ISLAND ST. JOHN'S WORT
Score: 1.50
Plant Profile
Known OC sites:
-
Dana Point:
-
In Headlands Hilltop Conservation Park, above Street of the Green Lantern
-
-
San Juan Capistrano: near La Novia Avenue & Valle Road, & on ridge above, 4.17 acres gross area.
-
Laguna Canyon, from approx. opposite the Festival of the Arts to approx. Laguna College of Art & Design at Big Bend
Total Orange County infestation estimated: Discontinuous over up to 40+ acres
Status Update:
Since at least the 1970's a colony has been present in San Juan Capistrano (per Fred Roberts). During that period, the colony's margin has expanded, but it has not appeared to have moved to adjoining lands. Little if any management has taken place that this colony in the ensuing years. However, in 2021 a portion of the colony was removed, by coincidence, during a housing and commercial development.
An old colony near the Dana Point Headlands was aggressively managed during the 1990's-2,000's. Most of the plant were successfully removed. A few occasionally return and continue to be managed.
On May 18, 2017 a detection in Laguna Canyon was reported through this Emergent Invasive Program, by Dr. Peter Bryant. It was quickly field checked, roughly mapped and can be seen on Calflora (HERE). This is a significant infestation of a highly problematic plant. The colony was well established and spread over approximately one linear mile of the canyon side, primarily on the SE side. The Laguna Canyon Foundation, with support from the City of Laguna Beach quickly initiated aggressive management in 2018 and continues management currently, with a goal of eradication. A few plants on private property may be a challenge.
Melinis repens - NATAL GRASS Emergent Invasive
Melinis repens - NATAL GRASS or RUBY GRASS
Score: 1.50
Plant Profile
Known OC sites:
-
Niguel Hill area in scattered locations, Laguna Niguel
-
Santa Ana Canyon, at Gypsum Cyn. and +- .6 mi East
-
Avenida San Pablo, San Clemente
Total Orange County infestation estimated: 4.61 acres mapped, plus unmapped acreage.
Status Update:
A single seeding plant was located and removed by OC CNPS along the Santa Ana River Bike Trail, 1 mile E of Gypsum Canyon Road. Area searched, but no others located. Record posted to Calflora.
Care should be taken not to confuse this species with the similar horticultural species, M. nerviglumis, which is not invasive.
Plants through the Niguel Hill area appear to be from hydroseed on HOA slopes, either intentionally or as a seed contaminant. The plant is now moving from these urban interface slopes into wildland locations. No management appears to be underway. These colonies are almost certainly the result of a hydroseed application in HOA urban edge landscaping.
Management is uncertain at the Gypsum Canyon and Santa Ana Canyon infestation, but is likely by the Irvine Ranch Conservancy.
Parthenium hysterophorus - SANTA MARIA FEVERFEW Emergent Invasive
Parthenium hysterophorus - SANTA MARIA FEVERFEW
Score: 1.00
Plant Profile
Known OC sites:
-
Santa Ana, SE corner of Lincoln Ave and 17th Street
-
Irvine, San Diego Creek channel, between Culver (Irvine) and Edinger Ave. (Tustin)
Total Orange County infestation estimated: .5+ acres.
Status Update:
In April, 2015, the first detection (and collection) in CA is made by a Jan West (specific identity is unknown) in urban Santa Ana.
In Aug, 2016, OCCNPS member Barbara Boethling detected a single plant in San Diego Creek Channel, adjacent to the San Joaquin Freshwater Marsh and Audubon offices. The plant is removed by OCCNPS and the surrounding area surveyed. No additional plants are found. Subsequent surveys continue over the next two years with 3-4 additional plants found and removed by OCCNPS. In July 2018 OCCNPS member Jonathan Frank discovers large population of up to 1,000 plants over a few acres approximately one mile further upstream. These plants were reported to OC Public Works, who begin management.
Management of this colony continues sporadically; however it has expanded considerably and now exists nearly two miles further up the channel.
Meanwhile, the Santa Ana colony is in a very urban location, adjacent to railroad tracks and urban landscaping. This colony was initially treated by OC Public Works in 2016, but with no subsequent management. Plants here have been managed several times by OCCNPS, but the population continues, although with no wildlands in the vicinity. This location may be the origins of the CA plants, as the species is occasionally used in homeopathic medicine by some cultures.
This species was given an A Rating by CDFA at the urging of OCCNPS, but management is very piecemeal and ineffective at present. These colonies persist as the point of entry and future establishment in CA for this very problematic invasive plant.
Rubus armeniacus - HIMALAYAN BLACKBERRY Emergent Invasive
Rubus armeniacus - HIMALAYAN BLACKBERRY
Score: 2.00
Plant Profile
Known OC sites:
-
Chino Hills: unspecified location(s)
-
Huntington Beach: Huntington Central Park
-
Laguna Hills: at small pond southeast of Moulton Parkway & Ridge Route. 355 square meters gross area.
-
San Juan Capistrano, El Horno Creek at Rancho Viejo Rd.
-
Silverado Canyon:
-
Hills above the road - nonspecific location
-
Lower Silverado Canyon: Drainage on eastern edge of Irvine Ranch Open Space, west of Horse stables
-
Upper Trabuco Canyon, nr. Falls Canyon
-
Aliso Creek, nr. Aliso Niguel High School
-
Park Avenue, Laguna Beach
-
-
Santiago Canyon (=Modjeska Cyn.), near the Community Center
-
Upper Newport Bay:
-
Big Canyon, below apartments, on HOA/City of Newport Beach property
-
Total Orange County infestation estimated: 2-4 acres.
To see a detailed list and map of all O.C. Calflora records, click HERE
To see additional photos from CalPhotos, click HERE
Status Update:
This highly problematic rambling vine is a major invasive in many parts of California and the west coast, but is still emergent in Orange County. Unfortunately, very little management is underway on these colonies, likely due to the challenges involved in management.
The well-established colony at Huntington Central Park received some good management between the years of approximately 2018-2021. Many plants were removed, but the colony is far from extirpated.
The Trabuco and Santiago Canyon colonies should be a priority for the US Forest Service, esp. the Trabuco colony given its location in an otherwise intact riparian community and its potential to spread in the watershed.
The Big Canyon colony at Upper Newport Bay should also be a priority given its adjacency to the sensitive Upper Newport Bay Preserve and the small colony size.
The Aliso-Wood Canyon and Park Avenue sites are assumed to be under management by the Laguna Canyon Foundation. And the Silverado Canyon colony is assumed to be under management by the Irvine Ranch Conservancy and/or OCTA.
The El Horno Creek and Laguna Hills colonies are under no management.
Senecio angustifolius Emergent Invasive
Score: 1.25
Plant Profile
Known OC sites:
-
Agua Chinon Wash, Irvine (possibly extirpated)
-
Harding Canyon, Cleveland National Forest, Santa Ana Mts.
-
Red Rock Canyon, Whiting Ranch Wilderness Park
Total Orange County infestation estimated: .1 acres
Status Update:
This is a relatively new invasive in California, first recorded on Aug. 17, 2010, at Camp Pendleton, USMC where it has since spread. In Feb. 2016, Josie Bennett (then with the Irvine Ranch Conservancy) found a single plant in the Agua Chinon, East of Irvine. Then, on Nov. 18, 2018, another single plant was located in Harding Canyon by OCCNPS member Jonathan Frank. Shortly thereafter, on Nov. 25 a colony suspected also by Jonathan Frank, was confirmed in Red Rock Canyon, Whiting Ranch.
All colonies have been thoroughly surveyed by OCCNPS, the Irvine Ranch Conservancy and/or OC Parks for additional plants. The Agua Chinon area around the detection was checked again by OCCNPS and IRC, but no plants could be located. The single Harding Canyon plant was removed and no others have been located, even after several OCCNPS checks.
The plants in Red Rock Canyon are now the primary concern. This is a small colony with most plants over perhaps 100 sq. meters, but a few isolated in another pocket a km or so further up the canyon. OC Parks, with assistance from OCCNPS and volunteers have been aggressively managing this colony, with a goal of extirpation.
The CA Invasive Plant Council, with assistance from OCCNPS, is currently performing a scientific review of the invasive status of this species. Little is known currently of its biology and invasiveness, with this CA infestations appearing to be the first occurences outside of its native South Africa.
Senecio linearifolius var. linearifolius - LINEAR-LEAVED AUSTRALIAN FIREWEED Emergent Invasive
Senecio linearifolius var. linearifolius - LINEAR-LEAVED AUSTRALIAN FIREWEED
Score: 2.00
Plant Profile
Known OC sites:
-
Irvine:
-
Shady Canyon Drive & Bonita Canyon Road.
-
Below the San Joaquin Reservoir, near Bonita Cyn. Dr. and Chambord
-
University Drive & Culver Drive, in Mason Park
-
-
Laguna Niguel/Dana Point:
-
Esp. in the Salt Creeks corridor and along Pacific Island Drive, etc.
-
-
Mission Viejo:
-
Along a 2-3 mi. stretch of Oso Creek
-
Total Orange County infestation estimated: 6+ acres, plus additional unmapped acreage.
To see a detailed list and map of all O.C. Calflora records, click HERE
To see additional photos from CalPhotos, click HERE
Status Update:
The first detection in California of this invasive plant was in a single plant in the Oso/Trabuco Creek area in 1985. Another was not found until 1998 in Irvine, near UCI. It is now firmly also established in San Diego County. Beginning in 2020 it has been reported in the San Francisco Bay area and as far North as Mendocino County.
In Orange County, the species is now well disturbed and expanding, esp. in the South OC areas of Laguna Niguel and Dana Point. The expanding colony along Pacific Island Drive in Laguna Niguel has had no management and those in the Salt Creek drainage have had very minimal management. The Irvine and Mission Viejo (Oso/Trabuco Creeks) are also not receiving any management.
This plant is expanding in Orange County and may soon be past an emergent stage.
Volutaria tubuliflora - EGYPTIAN KNAPWEED Emergent Invasive
Volutaria tubuliflora - EGYPTIAN KNAPWEED
Score: 2.00
Plant Profile
Known OC sites:
-
Upper Newport Bay:
-
Big Canyon area of Upper Newport Bay, Newport Beach.
-
On the mesas along Irvine Blvd. on the West side of the bay.
-
Total Orange County infestation estimated: 2-4 acres
To see a detailed list and map of all O.C. Calflora records, click HERE
To see additional photos from CalPhotos, click HERE
Status Update:
For an excellent discussion of this species in Southern California see the article by Frank Harris, Kate Harper, Tom Chester, and Ron Vanderhoff HERE.
For a brief article specific to the Orange County population, see the article by Ron Vanderhoff HERE.
In Orange County, this highly invasive species is known only from Upper Newport Bay. On March 31, 2014, OCCNPS member Barbara Boethling noticed an unusual plant in the Big Canyon area of Upper Newport Bay and sent photographs through this Invasive Plant Program to OCCNPS. The usual plant was identified as this species and within 24 hours the site was visited and additionally surveyed. In Jan. 2016 Dr. Peter Bryant located additional plants across the bay near the Muth Center/Irvine Blvd.
Both colonies have since been thoroughly surveyed and management has been rigorous, with partners including CDFW, OC Parks, City of Newport Beach, Newport Bay Conservancy, Irvine Ranch Conservancy, OCCNPS, Cal-IPC, the Natural Communities Coalition, UCCE, and others. This has been one of the most comprehensive and collaborative invasive plant efforts in OC. Annual management has been ongoing since the first detection, with numbers much reduced, from thousand to low hundreds. The Newport Bay Conservancy has become the lead agency for management.
During research on a related species OCCNPS made an important discovery about this species origins in California. OCCNPS discovered possible records dating to as early as 1987 at UNB. A photograph and comments of "Centaurea muricata" by Robert DeRuff (deceased) is made in The Vascular Plants of Upper Newport Bay.
A voucher specimen of the same record was deposited at the UC Riverside herbarium, also under the name Centaurea muricata. We now know that these records refer to Volutaria tubuliflora. In the records Mr. DeRuff mentions both Big Canyon and the bluffs not far from the Muth Center, both locations of our 2015 and 2016 records.
The specimen at UCR was confirmed V. tubuliflora and moves the date of California introduction forward by at least several years and also changes the introduction point from Borrego Springs to Newport Beach.
FORMER EMERGENT SPECIES
These species were previously Emergent Invasive in Orange County. They are no longer rated Emergent, but are still significant detection and management concerns. New detections should be documented on Calflora and/or iNaturalist.
Araujia sericifera - BLADDERFLOWER Former Emergent 2016
FORMER EMERGENT SPECIES
Araujia sericifera - BLADDERFLOWER?
Score: 2.75
Plant Profile
See all Orange County Calflora records HERE
To see additional photos from CalPhotos, click HERE
Orange County Status:
Now present through much of the lowlands of Orange County. Formerly a weed of citrus and tree crops, the vining perennial is now relatively common in loosely maintained urban landscaping. In wildlands it primarily occurs on the urban edge, especially in moist riparian habitats.
Asphodelus fistulosus - ONIONWEED Former Emergent 2016
FORMER EMERGENT SPECIES
?
Asphodelus fistulosus - ONIONWEED?
Score: 2.25
Plant Profile
See all Orange County Calflora records HERE
To see additional photos from CalPhotos, click HERE
Orange County Status:
This species is now well past the Emergent stage in Orange County. It is especially present in urban edge environments and along adjacent gentle slopes and washes. Primarily known from foothill and coastal locations. Likely introduced either intentionally or as a seed contaminant is seed mixes applies to urban slopes it has now established widely. A difficult plant to manage, as the entire root system must be removed. Many herbicides are also only marginally effective.
Of special concern are plants or colonies beyond the urban edge and encroaching on wildlands communities.
Brassica tournefortii - SAHARA MUSTARD Former Emergent 2016-2017
FORMER EMERGENT SPECIES
Brassica tournefortii - SAHARA MUSTARD
Score: 2.50
Plant Profile
See all Orange County Calflora records HERE
To see additional photos from CalPhotos, click HERE
Orange County Status:
This very aggressive annual mustard has quickly invaded Orange County as well as most of the Southern half of California. Its environmental plasticity is especially challenging, as it appears to be nearly as happy in coastal habitats as it is in the dry interior deserts. A prolific producer of seed along with its very early germination add to its abundance.
Its first report in Orange County was as recent as 1986, with the next not until 2003. Since then it has spread quickly. Initially primarily known in California from the western deserts it then moved to the inland valleys of Southern California. It then leaked into Orange County primarily via Santa Ana Canyon, but invariably was spread into the county via seed from other sources as well (equipment, clothing, animals, etc.).
It is especially suited to sandy, disturbed soils and often initiates infestations along trailsides, sandy wash margins, orchard edges and ruderal areas, but then moves into more intact plant communities.
Management continues in many areas of Orange County, especially high value locations. Examples of these still somewhat isolated infestations are at Caspers Park and portions of the San Joaquin Hills (Laguna Coast, etc.), where it is still likely emergent.
Detections of this species should continue to be reported and mapped on Calflora and/or iNaturalist.
Delairea odorata - CAPE IVY Former Emergent 2016-2019
FORMER EMERGENT SPECIES
Score: 2.25
Plant Profile
See all Orange County Calflora records HERE
To see additional photos from CalPhotos, click HERE
Orange County Status:
In wildlands, this is an environmental weed primarily of moist canyon bottoms, riparian communities and shaded brushy oak woodlands. The plant is also occasional in loosely maintained urban landscapes, where it rambles along the ground or climbs through and over other plants.
In Orange County it seems to be especially prevalant in the Laguna Beach area, but also with plants in the mountain foothill canyons. Plants and colonies are generally near urban areas, canyon homes, cabins, etc.
Management is especially difficult because of its twining, overtopping habit, usually intermixed with native plants. Also its propensity to re-root at nodes that come into contact with soil.
Of special significance for management are those colonies that are away from urban areas and growing in otherwise healthy environments, or adjacent to them. Examples include Emerald Canyon (Laguna Beach), Hot Springs Canyon, Silverado Canyon, Modjeska (=Santiago) Canyon, and near the mouth of San Mateo Creek (San Diego Co.).
New wildlands detections should be reported.
Dittrichia graveolens - STINKWORT Former Emergent 2016-2020
FORMER EMERGENT SPECIES
Dittrichia graveolens - STINKWORT
Score: 2.50
Plant Profile
See all Orange County Calflora records HERE
To see additional photos from CalPhotos, click HERE
Orange County Status:
The first California record of this highly problematic species was in the San Francisco area in 1984. It arrived in Orange County in 2011 with a detection by a member of the OCCNPS Invasive Committee in the Arroyo Trabuco area of O'Neill Regional Park. For a few years it was considered an Emergent Invasive species in Orange County. However, it has increased in occurrences and distribution to a level that no longer qualifies as Emergent.
Its current distribution is Orange County extends to several watersheds, both in mountain foothills as well all the way to the immediate coast. However, there are still many areas of the county where it has not been reported, especially the Northern portions. Any detections at new locations should be recorded and reported.
Often very aggressive management for the first few years of infestation, management has since relaxed somewhat. Land managers have varied responses to infestations. High value lands should continue to be protected from this very aggressive invasive plant.
Ehrharta calycina - PERENNIAL VELDT GRASS Former Emergent 2016-2020
FORMER EMERGENT SPECIES
Ehrharta calycina - PERENNIAL VELDT GRASS
Score: 1.25
Plant Profile
See all Orange County Calflora records HERE
To see additional photos from CalPhotos, click HERE
Orange County Status:
This species of the San Joaquin Hills has been a management target of Orange County's Natural Communities Coalition for many years (NCP/HCCP).
During its tenure in Orange County, this plant was thought to be reasonably well contained on a few hillsides, ridges, and slopes of coastal sage scrub/grasslands in the central San Joaquin Hills. However, in the late 2010's, James Bailey conducted invasive plant surveys throughout the area and expanded the range and number of plants considerably. At that point, the species was removed from the OCCNPS Emergent list.
Perennial Veldt Grass continues to be managed in the San Joaquin Hills, but no longer with an expectation of extirpation.
Because occurrences of this plant are still limited to portions of the San Joaquin Hills, any detections in other areas of the county should immediately be recorded on Calflora and/or iNaturalist. Identification can be problematic; please include very close-up images of the flowers (spikelets).
Emex spinosa - SPINY EMEX Former Emergent 2016-2017
FORMER EMERGENT SPECIES
Score: 2.50
Plant Profile
See all Orange County Calflora records HERE
To see additional photos from CalPhotos, click HERE
Orange County Status:
Spiny emex has been in Orange County for over 90 years, but occurred sporadically and was an insignificant environmental pest. However, beginning in the early 2010's the plant began spreading aggressively in the county, and elsewhere in Southern California. Only eight records prior to 2010 have exploded to nearly 300 since then. Is this an example of a "sleeper" population?
"Sleepers" are plants that persist in small numbers for years or decades, then with a change in an unknown environmental factor or an adaptive selection, become highly abundant and disruptive.
Currently spiney emex is well distributed and expanding in the almost all parts of the county, from the immediate coastal strand to the foothills, and often in dense stands.
Management was aggressive in the 2010's when the plant began expanding its distribution but today is irregular.
Iris pseudacorus - YELLOW FLAG IRIS Former Emergent 2016-2017
FORMER EMERGENT SPECIES
Iris pseudacorus - YELLOW FLAG IRIS
Score: 3.00
Plant Profile
See all Orange County Calflora records HERE
To see additional photos from CalPhotos, click HERE
This is a semi-aquatic plant always occurring either in standing water or immediately adjacent. It is also a plant of urban ponds and aquatic gardens.
In Orange County the primary wildlands infestation is in Laguna Canyon/Laguna Creek from near Lake Forest Drive to just South of the Marine Mammal Center, where the soft bodies creek is replaced by a concrete culvert. Infestations along this corridor can be quite common.
Elsewhere in Orange County isolated colonies are found at widely scattered locations. Caution should be taken by pond gardeners with this species as the seed and rhizomes are a threat to freshwater wetland communities, such as at the Laguna Lakes. Once in a drainage corridor the rhizomes are easily dislodged and moved downstream to re-root and enlarge the colony, resulting in hydrologic issues as well as loss of habitat.
All new infestations should be reported on Calflora and/or iNaturalist.
Lepidium draba - WHITETOP Former Emergent 2016
FORMER EMERGENT SPECIES
Score: 2.50
Plant Profile
See all Orange County Calflora records HERE
To see additional photos from CalPhotos, click HERE
Orange County Status:
Whitetop occurs in widely scattered locations through the lowland's areas of Orange County. In Orange County it has not spread prolifically, despite being present for over 100 years.
Populations generally occur in moist, disturbed sites, such as weedy fields, margins of roadways and other disturbed sites. Where is does occur its abundance seems to vary considerably, probably as a result of rainfall fluctuations.
Management is uncertain, but probably best reserved for high priority locations.
Lepidium latifolium - BROAD-LEAVED PEPPERGRASS Former Emergent 2016-2017
FORMER EMERGENT SPECIES
Lepidium latifolium - BROAD-LEAVED PEPPERGRASS
Score: 2.50
Plant Profile
See all Orange County Calflora records HERE
To see additional photos from CalPhotos, click HERE
Orange County Status:
One of the more troublesome invasive plants of freshwater and brackish water habitats. Although well distributed elsewhere in California, it has only expanded significantly in Orange County in the past twenty or so years. It is now present in many lowland freshwater habitats. Due to its rhizomatous nature and habit of intermixing with native riparian vegetation it is quite difficult to manage successfully. It spreads and infest from both seed dispersal, rhizomes and vegetative pieces that are dispersed by water.
If it is found in a new, unrecorded watershed or location it is important that it be reported promptly. Management success is improved significantly if the population is small.
Ludwigia hexapetala - CREEPING WATER PRIMROSE Former Emergent 2016
FORMER EMERGENT SPECIES
Ludwigia hexapetala - CREEPING WATER PRIMROSE?
Score:
Plant Profile
See all Orange County Calflora records HERE
To see additional photos from CalPhotos, click HERE
Orange County Status:
Ludwigia species can be difficult to locate and even more difficult to identify correctly. These are aquatic plants that generally require free water, often making their approach challenging. Further, the species can be rather cryptic and somewhat challenging to separate
This species is similar in appearance to the much more common Ludwigia peploides, which was for many years presumed to be native, but now assigned as a non-native invasive plant as well. L. hexapetala had sepal bases which are deltate (wide and flattened at the point of attachment), while L. peploides are lanceolate (narrow and tapering to the base).
L. hexapetala was known from Orange County by a single 2004 collection at Upper Newport Bay. However, no subsequent records have been made and surveys of the collection area have also been negative. Therefore that species has been removed from the Emergent Invasive list.
Nonetheless, this species does occur in Coastal Southern California and is also an occasional pond garden plant. Because of its difficulty in detection and identification it could be present in the county. Therefore, colonies of Ludwigia should be periodically examined carefully for this species and reported promptly if found.
Oncosiphon piluliferum - STINKNET Former Emergent 2016-2019
FORMER EMERGENT SPECIES
Oncosiphon piluliferum - STINKNET
Score: 2.75
Plant Profile
See all Orange County Calflora records HERE
To see additional photos from CalPhotos, click HERE
An invasive plant that has exploded in abundance in Southern California and Orange County and is causing significant environmental damage. California's first detection was in the Perris Valley in 1981 and Orange County's first report was in 2003 at the former El Toro Marine Base, where it quickly became abundant.
In the ensuing years in Orange County, the plant has spread to nearly all parts of the county, from the immediate coast to the high Santa Ana Mountains. It's ability to invade a wide variety of habitats and climatic extremes is especially concerning. Stinknet was especially noticeable in the Santa Ana Mountains during OCCNPS post-fire surveys following the 2018 Santiago Fire. This was one of the first plants to re-appear in the charred, barren soil, probably arriving from wind-blown seed coming in from the Elsinore Valley, where it is quite common.
Because of its current abundance, combined with often limited management resources, its control is irregular. High priority habitats and those not yet infested likely receive the most management. This is currently one of the most problematic invasive plants in Southern California.
Robinia pseudoacacia - BLACK LOCUST Former Emergent 2016
FORMER EMERGENT SPECIES
Robinia pseudoacacia - BLACK LOCUST?
Score: 3.50
Plant Profile
See all Orange County Calflora records HERE
To see additional photos from CalPhotos, click HERE
Plants and small to moderate colonies are scattered throughout Orange County from near the coast to the Santa Ana Mountains. Most occurrences are near abandoned houses, roadsides, and waste areas, but also naturalizes in riparian corridors and adjacent mesic slopes. The plant is too abundant in Orange County to be considered Emergent.
An occasional tree of urban landscapes, but usually disliked due to its size, messiness, and propensity to sucker and seed. The tree spreads both through abundant seed as well as vegetatively from rhizomes and can be difficult to remove or kill, often returning from suckers.
Seeds, leaves, and bark are all toxic and can even be fatal if ingested by humans or livestock.
Detections in new wildland locations, especially moist canyons of native vegetation should be recorded on Calflora or iNaturalist. Isolated plants adjacent to habitat should be carefully removed, including all root remnants, then monitored for a few years for re-sprouts or seedlings.
Salpichroa origanifolia - LILY-OF-THE-VALLEY-VINE Former Emergent 2016
FORMER EMERGENT SPECIES
Salpichroa origanifolia - LILY-OF-THE-VALLEY VINE?
Score: 2.00
Plant Profile
See all Orange County Calflora records HERE
To see additional photos from CalPhotos, click HERE
Orange County Status:
This species is no longer emergent based primarily upon its low levels of environmental disruption and propensity to be always adjacent to urban habitation.
Several colonies have recently been detected by the Laguna Canyon Foundation in the Laguna Beach area, including Laguna Canyon and especially the vicinity of Mission Hospital in South Laguna. Other detections are scattered.
A small colony at Crystal Cove State Park, present for several years, was reported by OCCNPS and treated by park staff in 2013, but has reappeared. A check of the site by OCCNPS revealed that plants have returned at the area near the day parking area at the El Moro entrance.
A single colonial clump was located by OC CNPS along the roadside in Hot Springs Canyon. The plants were removed, but some rhizomes were unable to be excavated. The location is being monitored for additional plants.
Any new detections, especially in wildlands locations, should be reported.
SPECIES REVIEWED BUT REJECTED
These species have been carefully reviewed for consideration as an Emergent Invasive Plant in Orange County, but have been rejected. They will continue to be assessed annually. A rejection may be for various reasons:
- Their distribution and abundance in the county have expanded past the Emergent level.
- Although naturalized in the county, the species has not proven significantly invasive, and causing environmental disruption.
- The occurrence(s) in the county are likely waifs and they have not been determined as persisting, naturalizing and being invasive.
- The species is primarily aquatic.
|
Botanical Name |
Common Name |
Date Added |
Score |
|---|---|---|---|
| Ageratina adenophora | STICKY SNAKEROOT | 2017 | 3.50 |
| Now well distributed in moist shaded drainages, coast to mountains. | |||
| Albizia lophantha | STINK BEAN | 2020 | 3.50 |
| Widely scattered locations. Ecological impacts appear to be low. | |||
| Commelina benghalensis | DAYFLOWER | 2018 | 3.50 |
| Often seen in weedy urban areas, But not significant or established in native vegetation. | |||
| Crassula colligata ssp. colligata | AUSTRALIAN PYGMYWEED | 2021 | 2.50 |
| First OC record in 2020. Environmental impacts not proven. | |||
| Dinebra retroflexa | VIPER GRASS | 2022 | 2.50 |
| A very small first OC detection in Irvine in 2021. Managed by OCCNPS and not re-found in future surveys. Waif status for now. | |||
| Elymus ponticus | TALL WHEAT GRASS | 2021 | 1.50 |
| A single mature plant detected and removed in 2020 in Aliso-Wood Canyon Wilderness Park. Monitoring. | |||
| Erodium malacoides | MEDITERRANEAN FILEREE | 2018 | 2.75 |
| A handful of scatterred detections since 2016. Species is being monitored for environmental impacts. | |||
| Euphorbia segetalis | GRAINFIELD SPURGE | 2020 | 1.50 |
| A 1st OC confirmation in 2019 (nr. Trabuco Canyon) and another in 2022 (South Laguna). Being monitored. | |||
| Genista monspessulana | FRENCH BROOM | 2020 | 1.00 |
| A small population near cabins in Holy Jim Canyon is partially managed, but continuing. Monitoring for invasiveness. | |||
| Geranium molle | CRANE'S BILL GERANIUM | 2020 | 2.75 |
| Three OC observations, but not appearing invasive. More problematic to the North. | |||
| Geranium robertianum | ROBERT'S GERANIUM | 2020 | 2.75 |
| Apparently established at the Fullerton Arboretum, but nowhere else in the county. | |||
| Geranium rotundifolium | ROUND LEAVED GERANIUM | 2020 | 2.75 |
| A few records in urban edges dating to 2017, but not established in wildlands. | |||
| Ipomoea cairica | MILE-A-MINUTE VINE | 2017 | 3.00 |
| Well established at several coastal locations, esp. along the South Coast and mostly in urban edge landscaping. Past Emergent. | |||
| Lathyrus tingitanus | TANGIER PEA | 2021 | 1.50 |
| Several colonies along SR74, in Riv. Co. A possible detection in Caspers Park and one confirmed in Silverado Cyn, both 2022. Being monitored. | |||
| Leucaena leucocephala | WHITE LEADTREE | 2020 | 3.00 |
| A significant invasive elsewhere. Here, primarily in riparian communities. Being monitored. | |||
| Limonium duriusculum | SEA LAVENDER | 2016 | 3.50 |
| Well distributed in the county and now well past the Emergent stage. | |||
| Limonium otolepis | ASIAN SEA LAVENDER | 2016 | 3.00 |
| A small clump rediscovered in 2021, following an old 1997 record. Managed immediately. Establishment uncertain. | |||
| Limonium preauxii | SEA LAVENDER | 2016 | 3.00 |
| Old records for Upper Newport Bay. Not relocated. Needs confirmation. | |||
| Limonium sventenii | SEA LAVENDER | 2016 | 3.00 |
| A 2008 record for Lake Forest. Not relocated. Needs confirmation of an extant population. | |||
| Liquidambar styraciflua | SWEETGUM | 2017 | 3.00 |
| Occasional waifs, but not confirmed as an environmental threat. | |||
| Pallenis maritima | GOLD COIN | 2022 | 3.00 |
| Small patches are established at scatterred locations on ocean-facing bluffs, but not determined as having environmental impacts. | |||
| Parietaria judaica | SPREADING PELLITORY | 2021 | 2.75 |
| A recent urban weed primarily in the Huntington and Sunset Beach areas. Not yet detected in wildlands. | |||
| Parthenocissus inserta | WOODBINE | 2021 | 3.00 |
| Silverado and Irvine colonies are being monitored. | |||
| Paspalum vaginatum | SEASHORE PASPALUM | 2017 | 2.25 |
| A significant invasive, but now well established at many freshwater/brackish water locations. | |||
| Pelargonium grossularioides | GOOSEBERRY PELARGONIUM | 2021 | 3.00 |
| Scatterred plants and small colonies, but it's ability to invade wildlands is not established, nor its environmental impacts. | |||
| Pennisetum villosum | FEATHERTOP | 2017 | 2.50 |
| Scatterred around the county, but not proven strongly aggressive or disruptive. | |||
| Phytolacca americana | AMERICAN POKEWEED | 2021 | 3.25 |
| A few recent records (>2019) but at ruderal urban areas. Not appearing as a wildland's invader. | |||
| Phytolacca icosandra | TROPICAL POKEWEED | 2021 | 2.50 |
| Also a few records >2017, but all in urban areas or ruderal waste areas. Not establishing in wildland's. | |||
| Pistia stratiotes (aquatic) | WATER LETTUCE | 2018 | 1.50 |
| Aquatic plants are not included in the final OCCNPS Emergent Invasive Plant List. | |||
| Plantago arenaria | INDIAN PLANTAIN | 2017 | 2.00 |
| Common at the Bolsa Chica Ecological and other coastal wetlands. Past the Emergent stage. | |||
| Plecostachys serpyllifolia | PETITE LICORICE | 2017 | 2.25 |
| Occasional patches along coastal bluffs and coastal canyons. Monitoring. | |||
| Ranunculus arvensis | FIELD BUTTERCUP | 2017 | 2.50 |
| Two collections from 2000 have not been re-observed. Assumed extirpated. | |||
| Ranunculus muricatus | BUTTERCUP | 2021 | 2.75 |
| Two small patches in urban, irrigated landscaping only. | |||
| Rapistrum ragosum | TURNIPWEED | 2021 | 1.00 |
| Ladd Cyn (2019) and Upper Newport Bay (2020) detections. Monitoring. | |||
| Salvinia minima (aquatic) | WATER SPANGLES | 2021 | 1.00 |
| Aquatic plants are not included in the final OCCNPS Emergent Invasive Plant List. | |||
| Salvinia molesta (aquatic) | KARIBA WEED | 2017 | 1.00 |
| Aquatic plants are not included in the final OCCPS Emergent Invasive Plant List. | |||
| Senna didymobotrya | AFRICAN WILD CASSIA | 2017 | 2.25 |
| Plants and small colonies are scatterred through the lowlands. Not yet determined as a wildland invasive and likely past Emergent. | |||
| Sesbania punicea | RATTLEBOX | 2021 | 1.25 |
| A single plant was rediscovered and removed at Upper Newport Bay in 2020, following a 2006 detection. Waifs, not considered established. | |||
| Solanum aviculare (laciniatum?) | NEW ZEALAND NIGHTSHADE | 2017 | 2.50 |
| Taxonomy is confused, may be conspecific. A colony persists in Hunt. Central Park, but invasiveness is not certain. | |||
| Tamarix aphylla | ATHEL TAMARISK | 2021 | 2.75 |
| Small colonies in Black Star Cyn. and near Rancho Santa Margarita are concerning. Monitoring. | |||
| Triadica sebifera | CHINESE TALLOWTREE | 2017 | 1.50 |
| Populations, esp. in San Clemente and Orange are being monitored. Not in wildlands. | |||
Select an invasive species from the list below to see the locations of known Orange County occurrences, as well as a status update from the chapter. Please do not report known Orange County occurrences. However, all new occurrences of these species should be documented and mapped to either Calflora (preferred) or iNaturalist. Alternatively, you may report these to using the instructions at Reporting an Invasive Plant.
Status updates include information on new occurrences, management activities, updates about the population, successes and failures and other news regarding each invasive species. If you have other updates or corrections, please report them for inclusion to .
For occasional brief summaries of recent invasive plant information also see Invasive Updates.
2022 EMERGENT INVASIVE PLANT SPECIES IN ORANGE COUNTY
Aegilops triuncialis - GOATGRASS Emergent Invasive
Aegilops triuncialis - GOATGRASS
Score: 1.00
Plant Profile
Known OC sites:
-
Audubon Starr Ranch
Status Updates (from management in which OC CNPS is involved):
A first report for Orange County was located in May 2015 over about 8 square meters in a grassland area at Audubon Starr Ranch. The detection was made by Jordan Isken, a biologist at the ranch. Management began immediately, with hand removal. Surveys and ongoing management have been consistent by the staff and interns at the ranch. No additional plants were located in 2016.
The small population at Starr Ranch has been under aggressive surveying and management since its detection. Through 2022, no plants have been found during the past few years, but surveys will continue until there is certainty of the seed bank being exhausted.
Brassica fruticulosa - MEDITERRANEAN CABBAGE Emergent Invasive
Brassica fruticulosa - MEDITERRANEAN CABBAGE
Plant Profile
Score: 1.25
Known OC sites:
- Harriett Weider Park, Bolsa Chica Marsh
- Sully Miller Pond, Huntington Beach (unconfirmed)
The first OC detection was made by Jesse Potter (then of the Bolsa Chica Conservancy) on Mar 18, 2020. OCCNPS botanists visited the site, took a collection, and confirmed the identification. The colony is under management by the Bolsa Chica Conservancy; however identification is challenging due to it resemblance to other non-native Brassicaceae, which are abundant in the area.
Spread to the immediately adjacent private oil properties is suspected but not confirmed due to access limitations.
On public lands management continues to be aggressive by the Bolsa Chica Conservancy and OC Parks.
Centaurea benedicta - BLESSED THISTLE Emergent Invasive
Centaurea benedicta - BLESSED THISTLE
Score: 2.25
Plant Profile
Known OC sites:
- San Juan Creek, Casper Wilderness Park
A single plant was detected and photographed on May 31, 2020, by OCCNPS member Diane Etchison in the San Juan Creek drainage at Caspers Park. It was re-found by Bob Allen six weeks later and re-photographed. Additional plants have not been found, even after several surveys over the past two years. This may have been a waif and has not established.
Centaurea diluta - SPOTTED KNAPWEED Emergent Invasive
Centaurea diluta - SPOTTED KNAPWEED
Score: 1.50
Plant Profile
Known OC sites:
- Villa Park Dam.
- Irvine Open Space along I-5 Fwy., between Jeffrey and San Canyon Rd.
- Two locations in Fullerton, about 1 km apart.
Total Orange County infestation estimated: +-29 acres
To see a detailed list and map of all O.C. Calflora records, click HERE
To see additional photos from CalPhotos, click HERE
Status Update:
This species has been known at least from the early 1970's from the Villa Park Dam site, just West of Irvine Park. Originally it was misidentified as Centaurea stoebe, but was corrected by OCCNPS botanists in the 2010's. For the next 45 years the plant has persisted at the Villa Park site and expended within the basin, but had not moved beyond. Thus, its invasiveness was in doubt, at least locally.
However, this may be changing and there is speculation that this may be a "sleeper" species, one in which the species lies fairly dormant for several generations, then one of the phenotypes adapts rather quickly to local conditions. At that point, a population explosion begins.
In 2019 a fairly small population was detected and confirmed in Fullerton and two years later another was detected about a kilometer away. Meanwhile, in 2019 a large population was detected in Irvine along the margin of an open space reserve.
The Irvine population is being managed by the Irvine Ranch Conservancy in cooperation with the City of Irvine. As far as we know there is no management of the Fullerton or Villa Park colonies.
This species is one in which we are particularly interested in new detections.
Centaurea solstitialis - YELLOW STAR THISTLE Emergent Invasive
Centaurea solstitialis - YELLOW STAR THISTLE
Score: 2.25
Plant Profile
Known OC sites:
-
Coal Canyon
-
Gypsum Canyon
-
San Juan Canyon, approx. nine or ten known colonies (some in Riv. Co.)
-
Caspers Wilderness Park, along SR74
-
Silverado Canyon: upper end past USFS gate
-
South Main Divide Road (Riv. Co.):
-
Elsinore Peak vicinity
-
Meadow (potrero) just south of Rancho Capistrano
-
Rancho Capistrano community
-
Total Orange County infestation estimated: 10-15 acres
To see a detailed list and map of all O.C. Calflora records, click HERE
To see additional photos from CalPhotos, click HERE
Status Update:
Several separated colonies along the margins of SR74 (the Ortega Highway) have been managed thoroughly since at least 2012 by OCCNPS, with all found plants removed
Annual pull counts for these SR74 colonies:
2014: 11,309 plants 2016: 2,543 plants 2018: 310 plants 2020: 1,777 plants 2022: 358 plants
2015: 1,556 plants 2017: 1,716 plants 2019: 1,116 plants 2021: 38 plants 2023: ?
Management of all SR74 colonies have been under aggressive management by OCCNPS volunteers and will continue.
Count fluctuations vary, mostly due to new detections of colonies and likely from variations in rainfall, roadside grading, and disturbances. New colonies were detected and added to the management in 2021, 2016, and 2015. Plants are removed on or about July 4 or one to two weeks prior depending on rainfall and plant phenology each year. This aligns with bud break and early flowering, but prior to the plants entering a reproductive stage.
A somewhat smaller population in upper Silverado Canyon, comprised of scattered subcolonies over 1-2 miles is also being aggressively managed by OCCNPS volunteers since 2014. These plants are also hand pulled with the cooperation and permission of The Cleveland National Forest. Counts have fallen significantly from the high of 2,056 pulled in 2015.
Infestations continue in the Northern Santa Ana Mountain foothills, especially in the Coal Canyon area (CA State Parks). Some management has been performed on these colonies. A large, extended colony in Gypsum continues toward SR241 and crosses it onto Caltrans land on the West side of the Northern Toll Plaza. It is being successfully managed in these locations by the Irvine Ranch Conservancy.
Smaller, emergent populations in lower Silverado Canyon, Caspers Park, Aliso-Wood Canyon Park, and Irvine Regional Park are all under management.
Chrysanthemoides monilifera - BONESEED Emergent Invasive
Chrysanthemoides monilifera ssp. monilifera - BONESEED
Score: 2.25
Plant Profile
Known OC sites:
- Laguna Beach:
- Near the mouth of Aliso Creek, along the sea bluff North & up the canyon just past the water district building.
- Hortense Miller Garden, Laguna Beach
- Vic of Boat Canyon Trail, Laguna Coast Wilderness Park.
- Newport Beach:
- Along Pacific Coast Highway, just SE of Morning Canyon Road.
Status Update:
This species was detected by OCCNPS near the mouth of Aliso Creek in Laguna Beach in Feb, 2013. Subsequent surveys have documented this colony extending to the coastal strand. With the exception of an uncertain population at Palomar College in San Diego County, this was the first detection of the species in California. This colony has spread North, up the beachfront to Treasure Island Beach. This colony is now known from additional intermittent plants scattered throughout the urban landscapes and urban edges of the area of Aliso Creek to about .4 mi N.
Additional plants were found naturalized in urban HOA landscaping in Corona del Mar. These pants are all plants still extant. A few plants at the former UCI Arboretum were removed at the request of OCCNPS. Old plants located at the Hortense Miller Garden in Laguna Beach are concerning. At the request of OCCNPS some of these plants were removed, but others persist. Given the adventuresome spirit of this garden, there is suspicion that this may have been the point of introduction of the species to CA, with seed and plants possibly distributed elsewhere.
In 2022 numerous additional plants were located naturalizing behind housing in the Boat Canyon area of Laguna Beach. These plants are not being managed.
A 2016 report from upper Nyes Place at an urban edge location was confirmed negative. It is a related Chrysanthmoides rotundata, a species that is not known to be invasive.
Currently the infestation is spread across a very non-contiguous area of 8.5 miles
In March 2015, with the urging of OC CNPS, CA Dept. of Food and Agriculture gave this species an A Rating, the highest rating available for a pest plant. The complete listing can be viewed here.
Dipogon lignosus - OKIE BEAN Emergent Invasive
Score: 1.50
Plant Profile
Known OC sites:
-
Mouth of Aliso Creek, Laguna Beach
-
NE margin of Bolsa Chica Marsh, Huntington Beach
-
Laguna Beach, four locations
Total Orange County infestation estimated: .5 acres.
Status Update:
This species was detected in wildlands for the first time in Orange County by James Bailey of OCCNPS near the mouth of Aliso Creek, in Laguna Beach on Aug. 14, 2020. This colony was visited by invasive plant management volunteers, led by Joan Miller, but the location of the colony was too dangerous for management. by that team. Management here has not yet begun, as far as we know.
In March and April of 2022 additional colonies were located in urban edge locations at three disjunct sites in Laguna Beach. These detections were made by Chris Gort of the Laguna Canyon Foundation. These colonies have all been field checked by OCCNPS. Most or all straddle private properties. No management is underway on these colonies.
A modest colony at an urban edge location at the Northern boundary of the Bolsa Chica Ecological Preserve was located in April, 2022. The colony appears to straddle private/public lands at a fenceline. The colony has been reported to land managers and biologist at the preserve. As far as we know, no management has begun.
Euphorbia terracina - GERALTON CARNATION WEED Emergent Invasive
Euphorbia terracina - GERALTON CARNATION WEED
Score: 1.50
Plant Profile
Known OC sites:
-
O'Neill Regional Park
-
Newport Peninsula, Newport Brach
Total Orange County infestation estimated: .1 acres
Status Update:
This highly invasive and disruptive species has been known for some time from just outside of OC. Plants grow within three miles of OC to the North in the Rowland Heights area. Additionally, a single plant was located in San Mateo Creek in San Clemente in 2020, within .4 km of Orange Co. at the Southern border.
On May 19, 2021, Johnny Iglesias, a biologist working at O'Neill Regional Park, detected a colony. It was field checked by OCCNPS, herbarium samples collected, delineated, and reported to OC Parks Natural Resources. The colony is over about 200 square meters of coastal sage scrub. Some management has begun, but the plants persist. This is a high priority and a point of infestation and potential spread.
Galenia pubescens - COASTAL GALENIA Emergent Invasive
Galenia pubescens - COASTAL GALENIA
Score: 2.00
Plant Profile
Known OC sites:
-
Water Tank Trail (Bommer Ridge), Laguna Coast Wilderness Park
-
Boat Canyon Trail, Laguna Coast Wilderness Park
Total Orange County infestation estimated: .1 acres mapped, plus unmapped acreage.
Status Update:
This species was first detected in Orange County on May 31, 2017, by OCCNPS member Jonathan Frank. Less than ten plants were detected in a very small patch off a trail variously called Water Tank Trail and Bommer Ridge Trail. The plants were removed and are checked regularly by OC Parks invasive plant volunteers led by Joan Miller. Plants were removed in 2018 and 2019 and none have been detected here since.
In May 2020, a larger colony was detected by OC Parks near the base of Boar Canyon Trail. This colony has number between 100-200 plants. It has been aggressively managed by OC Parks Invasive Plant volunteers since this time, with all plant being removed.
Hypericum canariense - CANARY ISLAND ST. JOHN'S WORT Emergent Invasive
Hypericum canariense - CANARY ISLAND ST. JOHN'S WORT
Score: 1.50
Plant Profile
Known OC sites:
-
Dana Point:
-
In Headlands Hilltop Conservation Park, above Street of the Green Lantern
-
-
San Juan Capistrano: near La Novia Avenue & Valle Road, & on ridge above, 4.17 acres gross area.
-
Laguna Canyon, from approx. opposite the Festival of the Arts to approx. Laguna College of Art & Design at Big Bend
Total Orange County infestation estimated: Discontinuous over up to 40+ acres
Status Update:
Since at least the 1970's a colony has been present in San Juan Capistrano (per Fred Roberts). During that period, the colony's margin has expanded, but it has not appeared to have moved to adjoining lands. Little if any management has taken place that this colony in the ensuing years. However, in 2021 a portion of the colony was removed, by coincidence, during a housing and commercial development.
An old colony near the Dana Point Headlands was aggressively managed during the 1990's-2,000's. Most of the plant were successfully removed. A few occasionally return and continue to be managed.
On May 18, 2017 a detection in Laguna Canyon was reported through this Emergent Invasive Program, by Dr. Peter Bryant. It was quickly field checked, roughly mapped and can be seen on Calflora (HERE). This is a significant infestation of a highly problematic plant. The colony was well established and spread over approximately one linear mile of the canyon side, primarily on the SE side. The Laguna Canyon Foundation, with support from the City of Laguna Beach quickly initiated aggressive management in 2018 and continues management currently, with a goal of eradication. A few plants on private property may be a challenge.
Melinis repens - NATAL GRASS Emergent Invasive
Melinis repens - NATAL GRASS or RUBY GRASS
Score: 1.50
Plant Profile
Known OC sites:
-
Niguel Hill area in scattered locations, Laguna Niguel
-
Santa Ana Canyon, at Gypsum Cyn. and +- .6 mi East
-
Avenida San Pablo, San Clemente
Total Orange County infestation estimated: 4.61 acres mapped, plus unmapped acreage.
Status Update:
A single seeding plant was located and removed by OC CNPS along the Santa Ana River Bike Trail, 1 mile E of Gypsum Canyon Road. Area searched, but no others located. Record posted to Calflora.
Care should be taken not to confuse this species with the similar horticultural species, M. nerviglumis, which is not invasive.
Plants through the Niguel Hill area appear to be from hydroseed on HOA slopes, either intentionally or as a seed contaminant. The plant is now moving from these urban interface slopes into wildland locations. No management appears to be underway. These colonies are almost certainly the result of a hydroseed application in HOA urban edge landscaping.
Management is uncertain at the Gypsum Canyon and Santa Ana Canyon infestation, but is likely by the Irvine Ranch Conservancy.
Parthenium hysterophorus - SANTA MARIA FEVERFEW Emergent Invasive
Parthenium hysterophorus - SANTA MARIA FEVERFEW
Score: 1.00
Plant Profile
Known OC sites:
-
Santa Ana, SE corner of Lincoln Ave and 17th Street
-
Irvine, San Diego Creek channel, between Culver (Irvine) and Edinger Ave. (Tustin)
Total Orange County infestation estimated: .5+ acres.
Status Update:
In April, 2015, the first detection (and collection) in CA is made by a Jan West (specific identity is unknown) in urban Santa Ana.
In Aug, 2016, OCCNPS member Barbara Boethling detected a single plant in San Diego Creek Channel, adjacent to the San Joaquin Freshwater Marsh and Audubon offices. The plant is removed by OCCNPS and the surrounding area surveyed. No additional plants are found. Subsequent surveys continue over the next two years with 3-4 additional plants found and removed by OCCNPS. In July 2018 OCCNPS member Jonathan Frank discovers large population of up to 1,000 plants over a few acres approximately one mile further upstream. These plants were reported to OC Public Works, who begin management.
Management of this colony continues sporadically; however it has expanded considerably and now exists nearly two miles further up the channel.
Meanwhile, the Santa Ana colony is in a very urban location, adjacent to railroad tracks and urban landscaping. This colony was initially treated by OC Public Works in 2016, but with no subsequent management. Plants here have been managed several times by OCCNPS, but the population continues, although with no wildlands in the vicinity. This location may be the origins of the CA plants, as the species is occasionally used in homeopathic medicine by some cultures.
This species was given an A Rating by CDFA at the urging of OCCNPS, but management is very piecemeal and ineffective at present. These colonies persist as the point of entry and future establishment in CA for this very problematic invasive plant.
Rubus armeniacus - HIMALAYAN BLACKBERRY Emergent Invasive
Rubus armeniacus - HIMALAYAN BLACKBERRY
Score: 2.00
Plant Profile
Known OC sites:
-
Chino Hills: unspecified location(s)
-
Huntington Beach: Huntington Central Park
-
Laguna Hills: at small pond southeast of Moulton Parkway & Ridge Route. 355 square meters gross area.
-
San Juan Capistrano, El Horno Creek at Rancho Viejo Rd.
-
Silverado Canyon:
-
Hills above the road - nonspecific location
-
Lower Silverado Canyon: Drainage on eastern edge of Irvine Ranch Open Space, west of Horse stables
-
Upper Trabuco Canyon, nr. Falls Canyon
-
Aliso Creek, nr. Aliso Niguel High School
-
Park Avenue, Laguna Beach
-
-
Santiago Canyon (=Modjeska Cyn.), near the Community Center
-
Upper Newport Bay:
-
Big Canyon, below apartments, on HOA/City of Newport Beach property
-
Total Orange County infestation estimated: 2-4 acres.
To see a detailed list and map of all O.C. Calflora records, click HERE
To see additional photos from CalPhotos, click HERE
Status Update:
This highly problematic rambling vine is a major invasive in many parts of California and the west coast, but is still emergent in Orange County. Unfortunately, very little management is underway on these colonies, likely due to the challenges involved in management.
The well-established colony at Huntington Central Park received some good management between the years of approximately 2018-2021. Many plants were removed, but the colony is far from extirpated.
The Trabuco and Santiago Canyon colonies should be a priority for the US Forest Service, esp. the Trabuco colony given its location in an otherwise intact riparian community and its potential to spread in the watershed.
The Big Canyon colony at Upper Newport Bay should also be a priority given its adjacency to the sensitive Upper Newport Bay Preserve and the small colony size.
The Aliso-Wood Canyon and Park Avenue sites are assumed to be under management by the Laguna Canyon Foundation. And the Silverado Canyon colony is assumed to be under management by the Irvine Ranch Conservancy and/or OCTA.
The El Horno Creek and Laguna Hills colonies are under no management.
Senecio angustifolius Emergent Invasive
Score: 1.25
Plant Profile
Known OC sites:
-
Agua Chinon Wash, Irvine (possibly extirpated)
-
Harding Canyon, Cleveland National Forest, Santa Ana Mts.
-
Red Rock Canyon, Whiting Ranch Wilderness Park
Total Orange County infestation estimated: .1 acres
Status Update:
This is a relatively new invasive in California, first recorded on Aug. 17, 2010, at Camp Pendleton, USMC where it has since spread. In Feb. 2016, Josie Bennett (then with the Irvine Ranch Conservancy) found a single plant in the Agua Chinon, East of Irvine. Then, on Nov. 18, 2018, another single plant was located in Harding Canyon by OCCNPS member Jonathan Frank. Shortly thereafter, on Nov. 25 a colony suspected also by Jonathan Frank, was confirmed in Red Rock Canyon, Whiting Ranch.
All colonies have been thoroughly surveyed by OCCNPS, the Irvine Ranch Conservancy and/or OC Parks for additional plants. The Agua Chinon area around the detection was checked again by OCCNPS and IRC, but no plants could be located. The single Harding Canyon plant was removed and no others have been located, even after several OCCNPS checks.
The plants in Red Rock Canyon are now the primary concern. This is a small colony with most plants over perhaps 100 sq. meters, but a few isolated in another pocket a km or so further up the canyon. OC Parks, with assistance from OCCNPS and volunteers have been aggressively managing this colony, with a goal of extirpation.
The CA Invasive Plant Council, with assistance from OCCNPS, is currently performing a scientific review of the invasive status of this species. Little is known currently of its biology and invasiveness, with this CA infestations appearing to be the first occurences outside of its native South Africa.
Senecio linearifolius var. linearifolius - LINEAR-LEAVED AUSTRALIAN FIREWEED Emergent Invasive
Senecio linearifolius var. linearifolius - LINEAR-LEAVED AUSTRALIAN FIREWEED
Score: 2.00
Plant Profile
Known OC sites:
-
Irvine:
-
Shady Canyon Drive & Bonita Canyon Road.
-
Below the San Joaquin Reservoir, near Bonita Cyn. Dr. and Chambord
-
University Drive & Culver Drive, in Mason Park
-
-
Laguna Niguel/Dana Point:
-
Esp. in the Salt Creeks corridor and along Pacific Island Drive, etc.
-
-
Mission Viejo:
-
Along a 2-3 mi. stretch of Oso Creek
-
Total Orange County infestation estimated: 6+ acres, plus additional unmapped acreage.
To see a detailed list and map of all O.C. Calflora records, click HERE
To see additional photos from CalPhotos, click HERE
Status Update:
The first detection in California of this invasive plant was in a single plant in the Oso/Trabuco Creek area in 1985. Another was not found until 1998 in Irvine, near UCI. It is now firmly also established in San Diego County. Beginning in 2020 it has been reported in the San Francisco Bay area and as far North as Mendocino County.
In Orange County, the species is now well disturbed and expanding, esp. in the South OC areas of Laguna Niguel and Dana Point. The expanding colony along Pacific Island Drive in Laguna Niguel has had no management and those in the Salt Creek drainage have had very minimal management. The Irvine and Mission Viejo (Oso/Trabuco Creeks) are also not receiving any management.
This plant is expanding in Orange County and may soon be past an emergent stage.
Volutaria tubuliflora - EGYPTIAN KNAPWEED Emergent Invasive
Volutaria tubuliflora - EGYPTIAN KNAPWEED
Score: 2.00
Plant Profile
Known OC sites:
-
Upper Newport Bay:
-
Big Canyon area of Upper Newport Bay, Newport Beach.
-
On the mesas along Irvine Blvd. on the West side of the bay.
-
Total Orange County infestation estimated: 2-4 acres
To see a detailed list and map of all O.C. Calflora records, click HERE
To see additional photos from CalPhotos, click HERE
Status Update:
For an excellent discussion of this species in Southern California see the article by Frank Harris, Kate Harper, Tom Chester, and Ron Vanderhoff HERE.
For a brief article specific to the Orange County population, see the article by Ron Vanderhoff HERE.
In Orange County, this highly invasive species is known only from Upper Newport Bay. On March 31, 2014, OCCNPS member Barbara Boethling noticed an unusual plant in the Big Canyon area of Upper Newport Bay and sent photographs through this Invasive Plant Program to OCCNPS. The usual plant was identified as this species and within 24 hours the site was visited and additionally surveyed. In Jan. 2016 Dr. Peter Bryant located additional plants across the bay near the Muth Center/Irvine Blvd.
Both colonies have since been thoroughly surveyed and management has been rigorous, with partners including CDFW, OC Parks, City of Newport Beach, Newport Bay Conservancy, Irvine Ranch Conservancy, OCCNPS, Cal-IPC, the Natural Communities Coalition, UCCE, and others. This has been one of the most comprehensive and collaborative invasive plant efforts in OC. Annual management has been ongoing since the first detection, with numbers much reduced, from thousand to low hundreds. The Newport Bay Conservancy has become the lead agency for management.
During research on a related species OCCNPS made an important discovery about this species origins in California. OCCNPS discovered possible records dating to as early as 1987 at UNB. A photograph and comments of "Centaurea muricata" by Robert DeRuff (deceased) is made in The Vascular Plants of Upper Newport Bay.
A voucher specimen of the same record was deposited at the UC Riverside herbarium, also under the name Centaurea muricata. We now know that these records refer to Volutaria tubuliflora. In the records Mr. DeRuff mentions both Big Canyon and the bluffs not far from the Muth Center, both locations of our 2015 and 2016 records.
The specimen at UCR was confirmed V. tubuliflora and moves the date of California introduction forward by at least several years and also changes the introduction point from Borrego Springs to Newport Beach.
FORMER EMERGENT SPECIES
These species were previously Emergent Invasive in Orange County. They are no longer rated Emergent, but are still significant detection and management concerns. New detections should be documented on Calflora and/or iNaturalist.
Araujia sericifera - BLADDERFLOWER Former Emergent 2016
FORMER EMERGENT SPECIES
Araujia sericifera - BLADDERFLOWER?
Score: 2.75
Plant Profile
See all Orange County Calflora records HERE
To see additional photos from CalPhotos, click HERE
Orange County Status:
Now present through much of the lowlands of Orange County. Formerly a weed of citrus and tree crops, the vining perennial is now relatively common in loosely maintained urban landscaping. In wildlands it primarily occurs on the urban edge, especially in moist riparian habitats.
Asphodelus fistulosus - ONIONWEED Former Emergent 2016
FORMER EMERGENT SPECIES
?
Asphodelus fistulosus - ONIONWEED?
Score: 2.25
Plant Profile
See all Orange County Calflora records HERE
To see additional photos from CalPhotos, click HERE
Orange County Status:
This species is now well past the Emergent stage in Orange County. It is especially present in urban edge environments and along adjacent gentle slopes and washes. Primarily known from foothill and coastal locations. Likely introduced either intentionally or as a seed contaminant is seed mixes applies to urban slopes it has now established widely. A difficult plant to manage, as the entire root system must be removed. Many herbicides are also only marginally effective.
Of special concern are plants or colonies beyond the urban edge and encroaching on wildlands communities.
Brassica tournefortii - SAHARA MUSTARD Former Emergent 2016-2017
FORMER EMERGENT SPECIES
Brassica tournefortii - SAHARA MUSTARD
Score: 2.50
Plant Profile
See all Orange County Calflora records HERE
To see additional photos from CalPhotos, click HERE
Orange County Status:
This very aggressive annual mustard has quickly invaded Orange County as well as most of the Southern half of California. Its environmental plasticity is especially challenging, as it appears to be nearly as happy in coastal habitats as it is in the dry interior deserts. A prolific producer of seed along with its very early germination add to its abundance.
Its first report in Orange County was as recent as 1986, with the next not until 2003. Since then it has spread quickly. Initially primarily known in California from the western deserts it then moved to the inland valleys of Southern California. It then leaked into Orange County primarily via Santa Ana Canyon, but invariably was spread into the county via seed from other sources as well (equipment, clothing, animals, etc.).
It is especially suited to sandy, disturbed soils and often initiates infestations along trailsides, sandy wash margins, orchard edges and ruderal areas, but then moves into more intact plant communities.
Management continues in many areas of Orange County, especially high value locations. Examples of these still somewhat isolated infestations are at Caspers Park and portions of the San Joaquin Hills (Laguna Coast, etc.), where it is still likely emergent.
Detections of this species should continue to be reported and mapped on Calflora and/or iNaturalist.
Delairea odorata - CAPE IVY Former Emergent 2016-2019
FORMER EMERGENT SPECIES
Score: 2.25
Plant Profile
See all Orange County Calflora records HERE
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Orange County Status:
In wildlands, this is an environmental weed primarily of moist canyon bottoms, riparian communities and shaded brushy oak woodlands. The plant is also occasional in loosely maintained urban landscapes, where it rambles along the ground or climbs through and over other plants.
In Orange County it seems to be especially prevalant in the Laguna Beach area, but also with plants in the mountain foothill canyons. Plants and colonies are generally near urban areas, canyon homes, cabins, etc.
Management is especially difficult because of its twining, overtopping habit, usually intermixed with native plants. Also its propensity to re-root at nodes that come into contact with soil.
Of special significance for management are those colonies that are away from urban areas and growing in otherwise healthy environments, or adjacent to them. Examples include Emerald Canyon (Laguna Beach), Hot Springs Canyon, Silverado Canyon, Modjeska (=Santiago) Canyon, and near the mouth of San Mateo Creek (San Diego Co.).
New wildlands detections should be reported.
Dittrichia graveolens - STINKWORT Former Emergent 2016-2020
FORMER EMERGENT SPECIES
Dittrichia graveolens - STINKWORT
Score: 2.50
Plant Profile
See all Orange County Calflora records HERE
To see additional photos from CalPhotos, click HERE
Orange County Status:
The first California record of this highly problematic species was in the San Francisco area in 1984. It arrived in Orange County in 2011 with a detection by a member of the OCCNPS Invasive Committee in the Arroyo Trabuco area of O'Neill Regional Park. For a few years it was considered an Emergent Invasive species in Orange County. However, it has increased in occurrences and distribution to a level that no longer qualifies as Emergent.
Its current distribution is Orange County extends to several watersheds, both in mountain foothills as well all the way to the immediate coast. However, there are still many areas of the county where it has not been reported, especially the Northern portions. Any detections at new locations should be recorded and reported.
Often very aggressive management for the first few years of infestation, management has since relaxed somewhat. Land managers have varied responses to infestations. High value lands should continue to be protected from this very aggressive invasive plant.
Ehrharta calycina - PERENNIAL VELDT GRASS Former Emergent 2016-2020
FORMER EMERGENT SPECIES
Ehrharta calycina - PERENNIAL VELDT GRASS
Score: 1.25
Plant Profile
See all Orange County Calflora records HERE
To see additional photos from CalPhotos, click HERE
Orange County Status:
This species of the San Joaquin Hills has been a management target of Orange County's Natural Communities Coalition for many years (NCP/HCCP).
During its tenure in Orange County, this plant was thought to be reasonably well contained on a few hillsides, ridges, and slopes of coastal sage scrub/grasslands in the central San Joaquin Hills. However, in the late 2010's, James Bailey conducted invasive plant surveys throughout the area and expanded the range and number of plants considerably. At that point, the species was removed from the OCCNPS Emergent list.
Perennial Veldt Grass continues to be managed in the San Joaquin Hills, but no longer with an expectation of extirpation.
Because occurrences of this plant are still limited to portions of the San Joaquin Hills, any detections in other areas of the county should immediately be recorded on Calflora and/or iNaturalist. Identification can be problematic; please include very close-up images of the flowers (spikelets).
Emex spinosa - SPINY EMEX Former Emergent 2016-2017
FORMER EMERGENT SPECIES
Score: 2.50
Plant Profile
See all Orange County Calflora records HERE
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Orange County Status:
Spiny emex has been in Orange County for over 90 years, but occurred sporadically and was an insignificant environmental pest. However, beginning in the early 2010's the plant began spreading aggressively in the county, and elsewhere in Southern California. Only eight records prior to 2010 have exploded to nearly 300 since then. Is this an example of a "sleeper" population?
"Sleepers" are plants that persist in small numbers for years or decades, then with a change in an unknown environmental factor or an adaptive selection, become highly abundant and disruptive.
Currently spiney emex is well distributed and expanding in the almost all parts of the county, from the immediate coastal strand to the foothills, and often in dense stands.
Management was aggressive in the 2010's when the plant began expanding its distribution but today is irregular.
Iris pseudacorus - YELLOW FLAG IRIS Former Emergent 2016-2017
FORMER EMERGENT SPECIES
Iris pseudacorus - YELLOW FLAG IRIS
Score: 3.00
Plant Profile
See all Orange County Calflora records HERE
To see additional photos from CalPhotos, click HERE
This is a semi-aquatic plant always occurring either in standing water or immediately adjacent. It is also a plant of urban ponds and aquatic gardens.
In Orange County the primary wildlands infestation is in Laguna Canyon/Laguna Creek from near Lake Forest Drive to just South of the Marine Mammal Center, where the soft bodies creek is replaced by a concrete culvert. Infestations along this corridor can be quite common.
Elsewhere in Orange County isolated colonies are found at widely scattered locations. Caution should be taken by pond gardeners with this species as the seed and rhizomes are a threat to freshwater wetland communities, such as at the Laguna Lakes. Once in a drainage corridor the rhizomes are easily dislodged and moved downstream to re-root and enlarge the colony, resulting in hydrologic issues as well as loss of habitat.
All new infestations should be reported on Calflora and/or iNaturalist.
Lepidium draba - WHITETOP Former Emergent 2016
FORMER EMERGENT SPECIES
Score: 2.50
Plant Profile
See all Orange County Calflora records HERE
To see additional photos from CalPhotos, click HERE
Orange County Status:
Whitetop occurs in widely scattered locations through the lowland's areas of Orange County. In Orange County it has not spread prolifically, despite being present for over 100 years.
Populations generally occur in moist, disturbed sites, such as weedy fields, margins of roadways and other disturbed sites. Where is does occur its abundance seems to vary considerably, probably as a result of rainfall fluctuations.
Management is uncertain, but probably best reserved for high priority locations.
Lepidium latifolium - BROAD-LEAVED PEPPERGRASS Former Emergent 2016-2017
FORMER EMERGENT SPECIES
Lepidium latifolium - BROAD-LEAVED PEPPERGRASS
Score: 2.50
Plant Profile
See all Orange County Calflora records HERE
To see additional photos from CalPhotos, click HERE
Orange County Status:
One of the more troublesome invasive plants of freshwater and brackish water habitats. Although well distributed elsewhere in California, it has only expanded significantly in Orange County in the past twenty or so years. It is now present in many lowland freshwater habitats. Due to its rhizomatous nature and habit of intermixing with native riparian vegetation it is quite difficult to manage successfully. It spreads and infest from both seed dispersal, rhizomes and vegetative pieces that are dispersed by water.
If it is found in a new, unrecorded watershed or location it is important that it be reported promptly. Management success is improved significantly if the population is small.
Ludwigia hexapetala - CREEPING WATER PRIMROSE Former Emergent 2016
FORMER EMERGENT SPECIES
Ludwigia hexapetala - CREEPING WATER PRIMROSE?
Score:
Plant Profile
See all Orange County Calflora records HERE
To see additional photos from CalPhotos, click HERE
Orange County Status:
Ludwigia species can be difficult to locate and even more difficult to identify correctly. These are aquatic plants that generally require free water, often making their approach challenging. Further, the species can be rather cryptic and somewhat challenging to separate
This species is similar in appearance to the much more common Ludwigia peploides, which was for many years presumed to be native, but now assigned as a non-native invasive plant as well. L. hexapetala had sepal bases which are deltate (wide and flattened at the point of attachment), while L. peploides are lanceolate (narrow and tapering to the base).
L. hexapetala was known from Orange County by a single 2004 collection at Upper Newport Bay. However, no subsequent records have been made and surveys of the collection area have also been negative. Therefore that species has been removed from the Emergent Invasive list.
Nonetheless, this species does occur in Coastal Southern California and is also an occasional pond garden plant. Because of its difficulty in detection and identification it could be present in the county. Therefore, colonies of Ludwigia should be periodically examined carefully for this species and reported promptly if found.
Oncosiphon piluliferum - STINKNET Former Emergent 2016-2019
FORMER EMERGENT SPECIES
Oncosiphon piluliferum - STINKNET
Score: 2.75
Plant Profile
See all Orange County Calflora records HERE
To see additional photos from CalPhotos, click HERE
An invasive plant that has exploded in abundance in Southern California and Orange County and is causing significant environmental damage. California's first detection was in the Perris Valley in 1981 and Orange County's first report was in 2003 at the former El Toro Marine Base, where it quickly became abundant.
In the ensuing years in Orange County, the plant has spread to nearly all parts of the county, from the immediate coast to the high Santa Ana Mountains. It's ability to invade a wide variety of habitats and climatic extremes is especially concerning. Stinknet was especially noticeable in the Santa Ana Mountains during OCCNPS post-fire surveys following the 2018 Santiago Fire. This was one of the first plants to re-appear in the charred, barren soil, probably arriving from wind-blown seed coming in from the Elsinore Valley, where it is quite common.
Because of its current abundance, combined with often limited management resources, its control is irregular. High priority habitats and those not yet infested likely receive the most management. This is currently one of the most problematic invasive plants in Southern California.
Robinia pseudoacacia - BLACK LOCUST Former Emergent 2016
FORMER EMERGENT SPECIES
Robinia pseudoacacia - BLACK LOCUST?
Score: 3.50
Plant Profile
See all Orange County Calflora records HERE
To see additional photos from CalPhotos, click HERE
Plants and small to moderate colonies are scattered throughout Orange County from near the coast to the Santa Ana Mountains. Most occurrences are near abandoned houses, roadsides, and waste areas, but also naturalizes in riparian corridors and adjacent mesic slopes. The plant is too abundant in Orange County to be considered Emergent.
An occasional tree of urban landscapes, but usually disliked due to its size, messiness, and propensity to sucker and seed. The tree spreads both through abundant seed as well as vegetatively from rhizomes and can be difficult to remove or kill, often returning from suckers.
Seeds, leaves, and bark are all toxic and can even be fatal if ingested by humans or livestock.
Detections in new wildland locations, especially moist canyons of native vegetation should be recorded on Calflora or iNaturalist. Isolated plants adjacent to habitat should be carefully removed, including all root remnants, then monitored for a few years for re-sprouts or seedlings.
Salpichroa origanifolia - LILY-OF-THE-VALLEY-VINE Former Emergent 2016
FORMER EMERGENT SPECIES
Salpichroa origanifolia - LILY-OF-THE-VALLEY VINE?
Score: 2.00
Plant Profile
See all Orange County Calflora records HERE
To see additional photos from CalPhotos, click HERE
Orange County Status:
This species is no longer emergent based primarily upon its low levels of environmental disruption and propensity to be always adjacent to urban habitation.
Several colonies have recently been detected by the Laguna Canyon Foundation in the Laguna Beach area, including Laguna Canyon and especially the vicinity of Mission Hospital in South Laguna. Other detections are scattered.
A small colony at Crystal Cove State Park, present for several years, was reported by OCCNPS and treated by park staff in 2013, but has reappeared. A check of the site by OCCNPS revealed that plants have returned at the area near the day parking area at the El Moro entrance.
A single colonial clump was located by OC CNPS along the roadside in Hot Springs Canyon. The plants were removed, but some rhizomes were unable to be excavated. The location is being monitored for additional plants.
Any new detections, especially in wildlands locations, should be reported.
SPECIES REVIEWED BUT REJECTED
These species have been carefully reviewed for consideration as an Emergent Invasive Plant in Orange County, but have been rejected. They will continue to be assessed annually. A rejection may be for various reasons:
- Their distribution and abundance in the county have expanded past the Emergent level.
- Although naturalized in the county, the species has not proven significantly invasive, and causing environmental disruption.
- The occurrence(s) in the county are likely waifs and they have not been determined as persisting, naturalizing and being invasive.
- The species is primarily aquatic.
|
Botanical Name |
Common Name |
Date Added |
Score |
|---|---|---|---|
| Ageratina adenophora | STICKY SNAKEROOT | 2017 | 3.50 |
| Now well distributed in moist shaded drainages, coast to mountains. | |||
| Albizia lophantha | STINK BEAN | 2020 | 3.50 |
| Widely scattered locations. Ecological impacts appear to be low. | |||
| Commelina benghalensis | DAYFLOWER | 2018 | 3.50 |
| Often seen in weedy urban areas, But not significant or established in native vegetation. | |||
| Crassula colligata ssp. colligata | AUSTRALIAN PYGMYWEED | 2021 | 2.50 |
| First OC record in 2020. Environmental impacts not proven. | |||
| Dinebra retroflexa | VIPER GRASS | 2022 | 2.50 |
| A very small first OC detection in Irvine in 2021. Managed by OCCNPS and not re-found in future surveys. Waif status for now. | |||
| Elymus ponticus | TALL WHEAT GRASS | 2021 | 1.50 |
| A single mature plant detected and removed in 2020 in Aliso-Wood Canyon Wilderness Park. Monitoring. | |||
| Erodium malacoides | MEDITERRANEAN FILEREE | 2018 | 2.75 |
| A handful of scatterred detections since 2016. Species is being monitored for environmental impacts. | |||
| Euphorbia segetalis | GRAINFIELD SPURGE | 2020 | 1.50 |
| A 1st OC confirmation in 2019 (nr. Trabuco Canyon) and another in 2022 (South Laguna). Being monitored. | |||
| Genista monspessulana | FRENCH BROOM | 2020 | 1.00 |
| A small population near cabins in Holy Jim Canyon is partially managed, but continuing. Monitoring for invasiveness. | |||
| Geranium molle | CRANE'S BILL GERANIUM | 2020 | 2.75 |
| Three OC observations, but not appearing invasive. More problematic to the North. | |||
| Geranium robertianum | ROBERT'S GERANIUM | 2020 | 2.75 |
| Apparently established at the Fullerton Arboretum, but nowhere else in the county. | |||
| Geranium rotundifolium | ROUND LEAVED GERANIUM | 2020 | 2.75 |
| A few records in urban edges dating to 2017, but not established in wildlands. | |||
| Ipomoea cairica | MILE-A-MINUTE VINE | 2017 | 3.00 |
| Well established at several coastal locations, esp. along the South Coast and mostly in urban edge landscaping. Past Emergent. | |||
| Lathyrus tingitanus | TANGIER PEA | 2021 | 1.50 |
| Several colonies along SR74, in Riv. Co. A possible detection in Caspers Park and one confirmed in Silverado Cyn, both 2022. Being monitored. | |||
| Leucaena leucocephala | WHITE LEADTREE | 2020 | 3.00 |
| A significant invasive elsewhere. Here, primarily in riparian communities. Being monitored. | |||
| Limonium duriusculum | SEA LAVENDER | 2016 | 3.50 |
| Well distributed in the county and now well past the Emergent stage. | |||
| Limonium otolepis | ASIAN SEA LAVENDER | 2016 | 3.00 |
| A small clump rediscovered in 2021, following an old 1997 record. Managed immediately. Establishment uncertain. | |||
| Limonium preauxii | SEA LAVENDER | 2016 | 3.00 |
| Old records for Upper Newport Bay. Not relocated. Needs confirmation. | |||
| Limonium sventenii | SEA LAVENDER | 2016 | 3.00 |
| A 2008 record for Lake Forest. Not relocated. Needs confirmation of an extant population. | |||
| Liquidambar styraciflua | SWEETGUM | 2017 | 3.00 |
| Occasional waifs, but not confirmed as an environmental threat. | |||
| Pallenis maritima | GOLD COIN | 2022 | 3.00 |
| Small patches are established at scatterred locations on ocean-facing bluffs, but not determined as having environmental impacts. | |||
| Parietaria judaica | SPREADING PELLITORY | 2021 | 2.75 |
| A recent urban weed primarily in the Huntington and Sunset Beach areas. Not yet detected in wildlands. | |||
| Parthenocissus inserta | WOODBINE | 2021 | 3.00 |
| Silverado and Irvine colonies are being monitored. | |||
| Paspalum vaginatum | SEASHORE PASPALUM | 2017 | 2.25 |
| A significant invasive, but now well established at many freshwater/brackish water locations. | |||
| Pelargonium grossularioides | GOOSEBERRY PELARGONIUM | 2021 | 3.00 |
| Scatterred plants and small colonies, but it's ability to invade wildlands is not established, nor its environmental impacts. | |||
| Pennisetum villosum | FEATHERTOP | 2017 | 2.50 |
| Scatterred around the county, but not proven strongly aggressive or disruptive. | |||
| Phytolacca americana | AMERICAN POKEWEED | 2021 | 3.25 |
| A few recent records (>2019) but at ruderal urban areas. Not appearing as a wildland's invader. | |||
| Phytolacca icosandra | TROPICAL POKEWEED | 2021 | 2.50 |
| Also a few records >2017, but all in urban areas or ruderal waste areas. Not establishing in wildland's. | |||
| Pistia stratiotes (aquatic) | WATER LETTUCE | 2018 | 1.50 |
| Aquatic plants are not included in the final OCCNPS Emergent Invasive Plant List. | |||
| Plantago arenaria | INDIAN PLANTAIN | 2017 | 2.00 |
| Common at the Bolsa Chica Ecological and other coastal wetlands. Past the Emergent stage. | |||
| Plecostachys serpyllifolia | PETITE LICORICE | 2017 | 2.25 |
| Occasional patches along coastal bluffs and coastal canyons. Monitoring. | |||
| Ranunculus arvensis | FIELD BUTTERCUP | 2017 | 2.50 |
| Two collections from 2000 have not been re-observed. Assumed extirpated. | |||
| Ranunculus muricatus | BUTTERCUP | 2021 | 2.75 |
| Two small patches in urban, irrigated landscaping only. | |||
| Rapistrum ragosum | TURNIPWEED | 2021 | 1.00 |
| Ladd Cyn (2019) and Upper Newport Bay (2020) detections. Monitoring. | |||
| Salvinia minima (aquatic) | WATER SPANGLES | 2021 | 1.00 |
| Aquatic plants are not included in the final OCCNPS Emergent Invasive Plant List. | |||
| Salvinia molesta (aquatic) | KARIBA WEED | 2017 | 1.00 |
| Aquatic plants are not included in the final OCCPS Emergent Invasive Plant List. | |||
| Senna didymobotrya | AFRICAN WILD CASSIA | 2017 | 2.25 |
| Plants and small colonies are scatterred through the lowlands. Not yet determined as a wildland invasive and likely past Emergent. | |||
| Sesbania punicea | RATTLEBOX | 2021 | 1.25 |
| A single plant was rediscovered and removed at Upper Newport Bay in 2020, following a 2006 detection. Waifs, not considered established. | |||
| Solanum aviculare (laciniatum?) | NEW ZEALAND NIGHTSHADE | 2017 | 2.50 |
| Taxonomy is confused, may be conspecific. A colony persists in Hunt. Central Park, but invasiveness is not certain. | |||
| Tamarix aphylla | ATHEL TAMARISK | 2021 | 2.75 |
| Small colonies in Black Star Cyn. and near Rancho Santa Margarita are concerning. Monitoring. | |||
| Triadica sebifera | CHINESE TALLOWTREE | 2017 | 1.50 |
| Populations, esp. in San Clemente and Orange are being monitored. Not in wildlands. | |||