Polygonum cuspidatum, Polygonum x bohemicum, Polygonum sachalinense
Perennial; small, white to green flowers in drooping clusters from leaf axils. Reddish brown and hollow stems. Leaves broad and ovate.
Photo credit: Jan Samanek
Photo credit: Nanna Borcherdt
Photo credit: Chris Evans
Photo credit: Steve Manning
Photo credit: Randy Westbrooks
Near water sources, along streams and rivers, wetlands, riparian areas and roadsides.
- Mature Height:
- Target Audience:
- water, garden clubs, water gardens
- ODA Listing:
- Plant Look Alikes:
- Bamboo, other knotweeds, common pokeweed
- Plant Impacts:
- Spreads quickly and forms dense thickets that displace native vegetation due to its aggressive growth. Creates bank erosion problems and is considered a potential flood hazard. Lowers quality of riparian habitat for fish and wildlife. Extremely vigorous rhizomes form deep, dense mat. Plants resprout from stem or root fragments creating new infestations downstream.
- Plant Links:
- King County Knotweed Info
- CWMA Actions List:
- volunteer response, contractor response