Alternanthera philoxeroides

Alligator weed

Family: Amaranthaceae · Type: perennial · Not Native

Conservation status: Cal-IPC Yes

Alligator weed is a naturalized perennial found in the San Joaquin Valley and Southern California coastal regions in shallow water, marshes, and pond edges at elevations below 200 meters. Flowering from May to October, this plant produces small white flowers in spherical clusters approximately 1.2 to 1.7 centimeters in diameter. Growing with prostrate, mat-forming stems 50 to 120 centimeters long that are white-hairy when young and become nearly hairless with age, it spreads extensively through stoloniferous growth. Its leaves are elliptic to obovate, 30 to 130 millimeters long and 5 to 35 millimeters wide, with a wedge-shaped base that may be slightly hairy and an obtuse or acute tip. The plant forms dense mats in wet environments, with young stems featuring distinctive white hairs along leaf axils and stem surfaces.

Habitat: Shallow water (< 2 m) or wet soils, marshes, edges of ponds

Bloom period: May-Oct

Elevation: < 200 m

Bioregions: SnJV, SCo

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