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Help Fight New Invasive Weed

A new invasive weed species has been identified in Carlsbad and other parts of San Diego County. Ward’s Weed is a small compact plant in the mustard family that almost looks like a tiny tumbleweed. It is easy to identify by its small yellow flowers with four petals and unique beaked seed pod. 

Ward’s Weed can grow as a thick mat that chokes out all other surrounding plant species. Due to the extremely high seed count of up to 30,000 seeds per plant per year, this species can spread quickly and also presents a fire hazard in our open spaces and canyons. 

The species is new to North America, but its current infestation is in a small enough geographic area that it is possible to eradicate before it gets out of control. Similar to the tumbleweed or Sahara mustard, which have spread throughout the western U.S., Ward’s Weed can do the same if not eliminated. In Australia, it was determined that a single introduction in 1915 eventually spread throughout the continent. 

What to do if you think you find Ward’s Weed 

  • 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.
  • Email Rosanne Humphrey, senior program manager, at rosanne.humphrey@carlsbadca.gov with the precise location. 

More Information
Rosanne Humphrey, senior program manager, 760-602-4689, rosanne.humphrey@carlsbadca.gov
Distribution map 
Ward's Weed information flier


April 1, 2019