Ambrosia psilostachya

Western ragweed, Western Ragweed

Family: Asteraceae · Type: perennial · Native

Western ragweed is a California native perennial found in the California Floristic Province in roadsides and dry fields at elevations below 1,000 meters. Flowering from June to November, this plant produces small greenish-white flowers in compact clusters on slender raceme-like stems. Growing with colonial stems 30 to 200 centimeters tall that emerge from rhizome-like roots, it spreads extensively in open disturbed areas. Its leaves are variable, with lower leaves opposite and upper leaves sessile, ranging 2 to 12 centimeters long, lanceolate to ovate with coarsely toothed or pinnately lobed edges marked by tiny resin glands. The fruit develops as a small brown bur with 0 to 7 tiny spines, giving the plant a distinctive bristly appearance.

Habitat: Common. Roadsides, dry fields

Bloom period: Jun-Nov

Elevation: < 1000 m

Bioregions: CA-FP

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