Polygonum aviculare

Knotweed, knotgrass, Knotgrass

Family: Polygonaceae · Type: annual · Not Native

Knotweed is a naturalized annual plant found in disturbed areas and open spaces across California. Flowering from June to September, this plant produces small white to red-margined flowers crowded in axillary clusters. Growing with prostrate to erect stems 10 to 60 centimeters long, it spreads across the ground in a sprawling, branched form. Its narrow elliptic to lanceolate leaves range from 6 to 50 millimeters long, varying from green to gray-green with flat margins. The plant produces small light to dark brown fruits with coarsely textured, angled surfaces that persist into late season.

California counties: Amador, Los Angeles, Orange, Ventura, San Bernardino, Santa Cruz, Mono, Santa Clara, Mariposa, San Francisco, Tulare, Butte, San Joaquin, Santa Barbara, San Diego, Fresno, Modoc, Contra Costa, Riverside, Marin, Lake, Sonoma, Stanislaus, San Luis Obispo, Alameda, San Mateo, Siskiyou, Sutter, El Dorado, Sacramento, Tuolumne, Colusa, Kern, Nevada, Yuba, Calaveras, Placer, Inyo, Alpine, Lassen, Monterey, Solano, Yolo, Plumas, Merced, Tehama, Shasta, Sierra, Madera, Trinity, Humboldt, Del Norte, Mendocino

Data from The California Species Project — 14,000+ California species with verified data from CNPS, CDFW, USFWS, Jepson eFlora, Cal-IPC, and more.