Walnut Creek, CA Landscaping Rules: Weed Ordinances (2026)

California Food & Agricultural Code Section 5004 and related sections give county agricultural commissioners authority over noxious weed control. Contra Costa County's list includes yellow starthistle (Centaurea solstitialis), artichoke thistle, French broom, Scotch broom, Spanish broom, pampas grass, giant reed, yellow and purple starthistle, and several others identified by the California Department of Food and Agriculture. Property owners are responsible for controlling these invasive weeds before they set seed. In Walnut Creek, the East Bay Regional Park District, Walnut Creek Open Space, and Save Mount Diablo actively manage adjacent preserves and encourage homeowners along the urban-wildland interface to remove brooms and starthistle from their property to prevent spread. Walnut Creek Code Enforcement can cite properties where noxious weeds contribute to fire hazard under the weed abatement ordinance, particularly in conjunction with annual ConFire inspections. Mechanical removal (pulling, mowing before seed set), targeted herbicide, and goat grazing are all acceptable methods. California prohibits planting most state-listed noxious weeds including pampas grass and giant reed.