Description: One of several foreign knotweeds introduced for garden purposes in the nineteenth century from the Himalayas and now established in a few places in the wild - on roadsides, maritime slopes etc. These wild colonies are the product of discarded garden rubbish containing bits of rhizome.

The leafy shoots grow up to about 6 feet high from underground rhizomes and produce clumps of small white or pale pink flowers in late summer.

Also called Polygonum polystachyum.

All names: Persicaria wallichii Greuter & Burdet; Persicaria polystachya (Wallich ex Meissner) Gross non Opiz; Polygonum polystachyum Wallich ex Meissner; Reynoutria polystachyum Wall. ex Meissner

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

iNaturalist: Persicaria wallichii at iNaturalist World Species Observations database.