Description: This is a vigorous perennial knotweed, forming huge clumps up to 10 feet high. It is similar to Japanese knotweed (Fallopia japonica), but rarer. Both male and female plants occur in Northern Ireland (unlike F. japonica which only produces female flowers in Ireland) and its pollen can fertilize F. japonica flowers to produce a rare hybrid when the two species grow near together.

A native of Korea, Japan and Sakhalin, introduced to Europe for gardens. It is found on riversides and waste ground, the products of discarded garden waste containing fragments of the plant.

All names: Fallopia sachalinensis (F.Schmidt ex Maxim.) Ronse Decraene; Reynoutria sachalinensis (F.Schmidt ex Maxim.) Nakai; Polygonum sachalinensis F.Schmidt ex Maxim.; Polygonum sachalinense F.Schmidt.

Distribution Map from NBN: Fallopia sachalinensis at National Biodiversity Network mapping facility, data for UK.

iNaturalist: Fallopia sachalinensis at iNaturalist World Species Observations database.