Polygonum polystachumhimalayan-knotweed


Family: Polygonaceae (Knotweed).

Other Common Names: None.

Origin: Himalayas and China.

Growth Form / Reproduction: Perennial. Creeping rhizomes and seeds.

Legal Status: None.

Agricultural: Knotweeds are eaten by grazing animals.
Ecological: Tall dense stands of knotweeds with their extensive network of rhizomes compete with native vegetation.
Human: Knotweeds have been used as landscape ornamentals; they are eaten where indigenous.

Habitat: Knotweeds prefer open sunny sites. They occupy diverse habitats and tolerate both moist and dry sites, on soils of silt, loams or sands. They spread most rapidly on moist disturbed sites such as ditches, streambanks and beaches.

Status and Distribution: Common in Comox Valley; limited distribution in Capital, Cowichan Valley and Strathcona. Found in the CWHxm and CDFmm.

Management Strategy: Once established, knotweeds are extremely difficult to control; the rhizomes extend meters beyond the clones and tiny fragments are able to regenerate. Digging or hand-pulling results in re-sprouting. Cutting, mowing, grazing and foliar herbicides can reduce top growth but repeated treatments are required for long-term control.

Additional Information:

Understanding & Controlling Invasive Knotweeds in BC by Jeff Hallworth

Invasive Plant Council of BC – TIPS Sheets

BC Ministry of Agriculture- Field Guide to Noxious Weeds

Sensitive Habitat Inventory Mapping, Knotweed ID guide

King County, USA, Best Management Practices for Knotweed