Desert Knapweed Containment


Volutaria tubuliflora, or desert knapweed, is a plant from north Africa that has recently been found in California. These are the only known sites in North America. There are two small sites on the coast in San Diego County and Orange County, and a major infestation in Borrego Springs, 50 miles inland in the Sonoran Desert. This infestation has spread over 15 square miles, and range modeling shows that desert knapweed would find suitable conditions across the American Southwest. in the 2016 superbloom, partners mapped and removed populations across the area during the January to April growing season. Multiple visits to each site were necessary since germination is spread out over the season, and the goal is to keep it from spreading more seed. Seed trials are underway to determine their capacity for dormancy to help determine the duration of effort that will be required, but we estimate at least a decade.

Plants being managed

Start date



Borrego Springs, Chula Vista and Newport Bay Southwest region

Resources protected

Desert wildflowers, habitat for flat-tail horned lizard.

Project goal

Our eventual goal is eradication, but our near-term goal is containment.

Project photos

Desert knapweed can grow large, competing for precious water. Photo by Pat Matthews.
Volutaria seedlings can be removed with a hula hoe. Photo by Mona Robison.
Volunteer with Saharan mustard (left hand) and desert knapweed. We hope to prevent Volutaria from spreading out of control like Saharan mustard. Photo by Pat Matthews.
Desert knapweed growing among desert wildflowers. Photo by Pat