Persicaria wallichii

Himalayan knotweed

Family: Polygonaceae · Type: perennial · Not Native

Conservation status: Cal-IPC Yes

Himalayan knotweed is a naturalized perennial herb found in northern California Coast and northern central Coast counties, particularly in Del Norte and Humboldt counties, in moist disturbed places and marshes at elevations below 500 meters. Flowering from August to October, this plant produces white to pink flowers in panicle-like clusters 40 to 120 millimeters long with distinctive red to purple anthers. Growing with ascending or erect stems 7 to 12 centimeters tall (occasionally to 250 centimeters), it develops adventitious roots and has a woody or non-woody base. Its large leaves measure 9 to 22 centimeters long, with cordate to truncate bases and acuminate tips, and are slightly hairy on the underside with glabrous or hairy upper surfaces. The fruit is a small, 3-angled brown achene measuring 2.1 to 2.5 millimeters long, often with a minutely rough texture.

Habitat: Moist disturbed places, marshes

Bloom period: Aug-Oct

Elevation: < 500 m

Bioregions: NCo (esp Del Norte, Humboldt cos.), n CCo

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