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Ward's Weed

Carlsbad is the epicenter of new invasive weed infestation. Ward’s Weed is a small compact plant that was first discovered in Carlsbad in 2008, which was the first discovery in North America. Now it has spread to approximately 200 acres of habitat within the city’s Habitat Management Plan preserves. 

See the treatment plan and schedule

What is Ward’s weed and how is it different from other weeds?

Ward’s weed is a highly invasive plant in the mustard family that is threatening our native habitat preserve system and increases the potential for wildfire. This plant can grow as a thick mat, choking out native plants, which in turn can result in less native pollinators, lizards, mice, birds and other animals. Ward’s weed is an annual, which means that it completes its life cycle, from sprout to producing seed, within one year, and then dies. Once dead, the plant dries up and can become easy to burn. 

Ward’s weed can be hard to identify because it can grow as single short sticks or a dense shrub-like plant that looks similar to a small tumbleweed. The best way to tell this plant apart from others is the spoon-shaped structure that sticks out from the small round seed pod.  

What makes Ward’s weed different from other weeds is that 99% of the known population in North America is in Carlsbad. The remaining 1% is in three small areas elsewhere in the County.  Also, because if its extremely high seed count of up to 30,000 seeds per plant per year, it has the potential to spread more quickly than many other weeds. We have a rare opportunity to eradicate this species before it spreads to the rest of California and the U.S.

Where is the Ward’s weed infestation?

The mapped Ward’s weed infestation is in the Bressi Ranch area, between El Camino Real and just east of Melrose, and between Palomar Airport Road and just south of Poinsettia Lane. Currently, about 200 acres of the habitat preserve lands are infested with Ward’s weed. See a map of the areas of infestation.

Why is it important to eradicate this weed?

The city has a legal obligation to safeguard the citywide native habitat preserve system. In addition, protection of our open space has consistently been identified by city residents as a core community value.  Ward’s weed threatens the health of our native habitats and species, and increases the wildfire risk.

Early, aggressive treatment will allow us protect our open space, reduce wildfire risk and prevent the spread of Ward’s weed to the rest of California and the U.S. in a cost effective manner. When an invasive species invades a new area, the cost of management is relatively low. As time goes on, the area covered by the plant increases very quickly and the cost of management also increases very quickly. Early on, it is possible to eradicate the species. But if this opportunity is missed, then the best we can do is to control it (keep it from spreading further). If it keeps spreading, then all that can be done is to manage it in priority areas. We believe that it is still possible to eradicate Ward’s weed.


What is the Carlsbad Ward’s weed eradication program?

On Oct. 8, 2019, Carlsbad City Council approved a program to eradicate Ward’s weed because of the threat to native habitats, protected plant and animal species, and recreational and agricultural areas in Carlsbad. Invasive, non-native species are one of the greatest threats to the city’s preserve system. It is not known how Ward’s weed got into the area.

The city is partnering with Nature Collective, San Diego County, and Center for Natural Lands Management to implement a large-scale effort to eradicate Ward’s weed while it is still possible. The Bressi Ranch area will be treated by ACS Habitat Management; the Rancho Carrillo area will be treated by San Diego County crews; and the Ranch La Costa Preserve (“The Greens”) will be treated by Center for Natural Lands Management. See general treatment map. These areas will be treated in a coordinated fashion to ensure that no habitat in the infested area (approximately 200 acres) is missed. The treatment consists of use of a pre-emergent herbicide Gallery, which stops seeds from germinating. This herbicide is safe for use in native habitat areas and will not harm existing native plants.

The treatment will be applied once, starting approximately in late November. The ideal treatment window is narrow. It must be applied just before the rains begin, before seeds begin to germinate, but not too early as the herbicide begins to break down within a couple of weeks. The exact start date and duration of the project depends on the weather. If it is a drought year, the project could be postponed until next year. After the initial treatment, follow up spot treatments may be necessary if areas were missed. After the initial coordinated treatment covering the entire infested area, follow up surveillance and maintenance will be required for a number of years to prevent a resurgence of this species.

Are the methods consistent with the city’s Integrated Pest Management Plan?

Yes. The city’s Integrated Pest Management Plan, approved by City Council Resolution No. 2017-229, allows the use of herbicide “if deemed necessary by supervisory staff to protect public safety; to prevent a threat to sensitive species or native habitats; to assist in meeting regulatory compliance requirements; or to prevent economic loss – when pests cannot be managed by any other tactics.”

Center for Natural Lands Management, in coordination with ACS Habitat Management and UC Cooperative Extension conducted 10 years of field trials to find the least toxic method of control for Ward’s weed, including hand-pulling, mechanical methods, organic herbicides and non-organic herbicides. None of these methods worked. The infestation was not being controlled.  Finally, field trials using Gallery, a pre-emergent herbicide which works by stopping seeds from germinating, worked exceptionally well, even in native habitat. Gallery stopped Ward’s weed seeds from sprouting but did not kill the existing native shrubs, forbs or bulbs.

How was this program funded?

Half of the program costs are being funded by grant funds obtained by Nature Collective and San Diego County. These grant sources include California Wildlife Conservation Board, Noxious Weed Grant Program (California Department of Food and Agriculture) and San Diego Regional Invasive Plant Early Detection and Rapid Response Program (SANDAG). The city is funding the other half of the program through budget savings from the previous fiscal year.

Is this program supported by conservation organizations and resource agencies?

Yes! The city has been partnering with a wide range of organizations and resource agencies, including:

  • Nature Collective (formerly San Elijo Lagoon Conservancy)
  • Center for Natural Lands Management (CNLM)
  • San Diego Management and Monitoring Program (SDMMP)
  • San Diego Habitat Conservancy
  • Batiquitos Lagoon Conservancy


  • San Diego County Department of Agriculture, Weights and Measures (County AWM)
  • San Diego Association of Governments (SANDAG)
  • California Department of Fish and Wildlife (CDFW)
  • US Fish and Wildlife Service (USFWS)
  • US Geological Society (USGS)
  • City of San Diego


When and where will the program start and how long will it take?

Treatment must be applied before rain and will begin in late November. Depending on amount of rainfall, treatment could last for just a few months or through late spring to cover the 200-acre area. Actual start date, schedule, and duration of the project will depend on things like weather conditions, site access, and site topography. The schedule will be updated regularly. 

How are you keeping the public safe?

  • The U.S. Environmental Protection Agency (EPA) classifies Gallery as category III (low toxicity)
  • Consistent with the city’s Integrated Pest Management Plan and state requirements, the city will post the areas of treatment at least 24 hours prior to spraying and leave the signs up 72 hours afterward.
  • Most of the infested areas are off limits to the public except for trails. All areas that could be accessed by the public will be posted and blocked off to keep people out of the treated areas until the herbicide has fully dried.
  • Detailed information about the program will be provided to the public onsite, including a phone number to call for questions or concerns.

Why is the spray area colored blue/green?

It is very important that no infested areas are missed because Ward’s weed will sprout in these areas and become a seed source for a new crop of Ward’s weed. A blue or green dye will be added to the herbicide as a marker to show which areas have been sprayed. This will ensure that no areas are missed and no areas are sprayed twice.

Which trails/sidewalks will be closed, when and for how long?

The main trail closures during this process will be El Fuerte Trail (Bressi Ranch Preserve) and Rancho Carrillo Trail (south of Poinsettia Lane). Trails will be closed long enough to treat the areas adjacent to the trail plus a minimum of two days to ensure that no one enters the treated area until the vegetation is dry. Drying generally takes a couple of hours but may dry more slowly depending on weather conditions. Certain smaller trail areas in the infested areas may be closed as needed. See current schedule

How can I prevent the spread of Ward’s weed?

Avoid infested areas. If you are in an infested area, decontaminate your boots and clothing as necessary (brushing, picking out mud from cracks of boot soles, etc), avoid clothing that sticks to plants (cotton, fleece, etc), and brush off your pet’s fur and foot pads. Stay on designated trails.

What else has the city been doing to prevent the spread of Ward’s weed?

The city has been working closely with the Home Owners Associations, Business Associations, and landscaping companies in the infested areas to make sure residents are informed and landscaping crews know the appropriate ways to deal with Ward’s weed. 

What should I do if I think I found it or if I have questions or concerns?

Take a close-up photograph and submit to the city for identification. If it is confirmed to be Ward’s weed, we will work with you to determine what to do. Please contact our Senior Habitat Management Program Manager at rosanne.humphrey@carlsbadca.gov or 760-602-4689.

Download the iNaturalist App on your smartphone. This will help to identify the plant when you take a photo. If it is Ward’s Weed, a local biologist with the San Diego Natural History Museum will receive the submission and confirm the identification. Our local biologists will then be able to access the record.

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