Riverside, CA Invasive Plant Rules: Prohibited Species (2026)

California regulates invasive and noxious plants statewide under California Food & Agricultural Code Sections 7270 and following, with the California Department of Food and Agriculture publishing the Noxious Weed list and rating system (A, B, C, Q). Riverside is particularly concerned with three invasive species along the Santa Ana River and its tributaries: Arundo donax (giant reed), which crowds out native willow and cottonwood and dramatically increases wildfire fuel loads; tamarisk (Tamarix ramosissima, salt cedar), which depletes groundwater and salinizes soils; and pampas grass (Cortaderia selloana/jubata), which establishes in disturbed areas and produces millions of windborne seeds. The Santa Ana Watershed Project Authority, U.S. Fish & Wildlife, and Riverside Conservation Authority coordinate removal in the river corridor. Homeowners in adjacent neighborhoods should not plant these species and should report established stands through Engage 311 for public-property sites. Other CDFA-listed invasives found locally include yellow star-thistle, perennial pepperweed, and artichoke thistle. The California Invasive Plant Council (Cal-IPC) maintains a complementary horticultural 'Don't Plant a Pest' list used by most Southern California nurseries.