E-Flora BC: Electronic Atlas of the Flora of British Columbia

Persicaria wallichii Greuter & Burdet
Himalayan knotweed
Polygonaceae (Buckwheat family)

Introduction to Vascular Plants

© Virginia Skilton  Email the photographer   (Photo ID #4836)

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Distribution of Persicaria wallichii
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Species Information

Perennial herb from strongly creeping rhizomes; stems erect, numerous, branched, 1-2 m tall, reddish-brown.
Basal leaves lacking; stem leaves alternate, lanceolate, the blades up to 20 cm long, densely soft- hairy, the base rounded to somehat heart-shaped, often with 2 small lobes, the stalks short; stipules sheathing, entire.
Inflorescence a wide, diffuse panicle; perianth segments white, 3-5 mm long, not keeled on the back.
Apparently sterile in our range.

Source: The Illustrated Flora of British Columbia

Habitat / Range

Mesic fields and waste places in the lowland zone; rare in extreme SW BC and the Queen Charlotte Islands; introduced from SC Asia.

Source: The Illustrated Flora of British Columbia

Additional Notes

Persicaria wallichii is considered an emerging invasive species in the Vancouver region by the Greater Vancouver Invasive Plant Council (2009). An emerging invasive is defined by them as: currently found in isolated, sparse populations but are rapidly expanding their range within the region.


The climate type for this species, as reported in the: "British Columbia plant species codes and selected attributes. Version 6 Database" (Meidinger et al. 2008), is not evaluated, unknown or variable.

Synonyms and Alternate Names

Aconogonum polystachyum
Polygonum polystachyum Wall. ex Meisn.

Taxonomic and Nomenclatural Links

Additional Photo Sources

General References