Family: Polygonaceae (Buckwheat)
Other Scientific Names: Polygonum sachalinensis, Reynoutria sachalinensis (F. Schmidt ex Maxim.) Nakai
Other Common Names: Sachaline
Growth Form / Reproduction: Perennial. Seeds and vegetatively from rhizomes.
Legal Status: Forest and Range Practices Act, Community Charters Act.
Agricultural: Knotweeds can provide forage for grazing animals.
Ecological: Dense stands can compete effectively with native plants.
Human: Knotweeds are used as landscape ornamentals; shoots are edible in spring.
Habitat: Moist disturbed sites, stream banks, roadsides, and railway corridors.
Status and Distribution: Present in all CIPC Regional Districts; widespread in Comox Valley, common in Cowichan Valley and Strathcona, limited in other regions. Most common in CDFmm and CWHxm but also present in the CWHvm.
Management Strategy: Shading with black plastic bags can provide some short-term control but is not practical for large areas. Cutting, mowing and grazing can temporarily control top growth but these treatments must be repeated numerous times per year for several years. Salt water treatments can give temporary top growth control. Foliar herbicides can control top growth but repeated treatments are required to control new sprouts. Stem injecting herbicides directly into the plant can be effective. No biocontrol agents are presently available.
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