The South Coast Region (Ventura & LA WMAs) Weed Prioritization Meeting
EDRR Target Weed List Update – Part 2. Thursday, November 5,  1:00 PM – 2:30 PM, online.
The Ventura and Los Angeles County WMAs, Cal-IPC, and the CDFA will go over the target species list. Contact Rachel Burnap to access the virtual meeting if you did not get the email notification.

EDRR

Early Detection, Rapid Response is becoming a priority for land managers, so there are a lot of current efforts in catching and eliminating weeds before they become established. Observations are critical to this effort and therefore highly encouraged on iNaturalist, or even better, Calflora.org. Help on how to use Calflora’s Observer app can be found on this page, or at Calflora’s observer help page.

The variety of areas within LA County

Current Projects

The LA WMA is very diverse, ranging from high desert to high mountains to coastal marshland with many geographic borders. Here are some projects from around the county:

UCLA Stunt Ranch Santa Monica Mountains Reserve

The dominant non-native plants in this area include: Black Mustard (Brassica nigra), Bermuda buttercup (Oxalis), Maltese star-thistle (Centaurea melitensis), Bur Clover (Medicago polymorpha), Non-Native Oat (Avena sp.), and Scarlet Pimpernel (Anagallis arvensis).

Another trophy weed at UCLA Stunt Ranch

Staff are restoring habitat through timed mowing and hand-pulling, and a newly established native plant nursery on site serves as the hub for sowing local seed and growing plants that will eventually be transplanted into designated restoration plots. Volunteers are central to this work. If you’d like to help restore habitat at Stunt Ranch, please reach out to site manager David Blake at dblake0405@g.ucla.edu.

Catalina Island Conservancy

The Catalina Island Conservancy’s Catalina Habitat Improvement and Restoration Program Invasive Plant Project (CHIRP-IPP) works to manage invasive plants across 48,000+ acre Catalina Island. The primary invasive plant challenge on Catalina is Mediterranean Broom (Genista linifolia). This species was introduced through horticulture in the early 1900s and since then has come to compose 5-10% of Catalina’s vegetation, particularly around the City of Avalon.

Early Detection Rapid Response (EDRR) is another major priority of CHIRP-IPP to further the protection of Catalina’s natural and cultural resources. Sightings reported via iNaturalist and Calflora are welcome. For further information regarding CHIRP-IPP please contact Aaron Kreisberg at akreisberg@catalinaconservancy.org. For information on volunteering with the Catalina Island Conservancy, contact volunteers@catalinaconservancy.org.

Palos Verdes Peninsula Land Conservancy (PVPLC)

Recently, the main target has been Acacia (Acacia cyclops), though they are working on many other species. They are also working on Stinkwort (Dittrichia graveolens) on the military base in San Pedro with the US Navy. Many of the efforts at PVPLC revolve around protecting habitat for the critically endangered Palos Verdes Blue Butterfly. Volunteers are vital to the work at PVPLC. To find out more, visit the volunteer page here.

Ailanthus before

& After

Bill Neill
Bill is doing invasive mitigation all around the northern LA County and has recently been working with Ventura Land Trust on Castor Bean (Ricinus communis). He is also working north of Griffith Park in the San Fernando Valley on Tree of Heaven (Ailanthus altissima).

PESE treatments in Lower Tuna Canyon

Restoring Fire-Affected Hillsides in the Santa Monica Mountains
The Santa Monica Mountains Fund restoration team has been working to protect native habitats recovering from recent fires including the 2025 Palisades Fire and 2018 Woolsey Fire. Working in partnership with the National Park Service, a dedicated crew has been identifying and removing invasive plants that threaten the recovery of the region’s coastal sage scrub and other native plant communities. Wildfires create opportunities for invasive plants to spread rapidly, particularly along disturbed roadsides, drainage areas, and fire access routes. In and around Topanga State Park, our team has encountered aggressive infestations of invasive species such as tree tobacco (Nicotiana glauca), castor bean (Ricinus communis), fountain grass (Pennisetum setaceum), and Cape ivy (Delairea odorata).

Cut-Stump treatments on Tree Tobacco

One recent success began with the discovery of a few invasive Harding grass (Phalaris aquatica) plants along a fire road. Further investigation revealed a much larger infestation extending across more than half an acre. Our team quickly developed and implemented a treatment strategy to prevent its continued spread into surrounding native habitat.

We’ve also discovered and treated some Early Detection and Rapid Response (EDRR) species like stinkwort (Dittrichia graveolens), woolly distaff thistle (Carthamus lanatus), and skeleton weed Chondrilla juncea). Persistent  treatments have paid off and EDRR species have been reduced to only trace amounts. From surveying remote hillsides to carefully removing invasive plants, this work requires persistence, adaptability, and a strong understanding of the local ecosystem. Each infestation controlled represents another opportunity for native plants to recover and thrive. With continued support from our partners and volunteers, we can protect the biodiversity of the Santa Monica Mountains and help these landscapes recover from wildfire. Join in at the link below!
Outdoors Calendar – SANTA MONICA MOUNTAINS FUND

Resources

Weed CUT
UC Agriculture and Natural Resources’ Weed Control User Tool provides a decision support tool that offers a reliable variety of treatment options. It gives you lots of choices and different ways to look up management practices.

UC Davis Weed Research and Information Center
This extensive site has weed management notes with write-ups detailing pest plants and a large resource database of articles regarding pest management.

LA County’s Best Management Practices for Vegetation Management
This thorough PDF is designed as a manual for prevention, eradication, and control of weeds. Additional information includes sample vegetation management plans.

Plant Right
This site helps steer people away from planting invasives. It is a good reference for gardeners and landscapers because it offers native alternatives to common invasives.

WMA General Contact:

Rachel Burnap, Los Angeles County Agricultural Weights and Measures RBurnap@acwm.lacounty.gov

site updated: 10/19/26