Page authors: Don Knoke, David Giblin
Persicaria wallichii
garden knotweed, Himalayan knotweed
WTU specimens
Other herbaria

Distribution: Occurring west of the Cascades crest in Washington; British Columbia south to California; also in eastern North America.

Habitat: Waste areas, roadsides, and other disturbed areas where often where somewhat moist.

Flowers: July-October

Origin: Introduced from eastern Asia

Conservation Status: Not of concern

Description:
General:

Vigorous, rhizomatous perennial with numerous, erect, reddish-brown, leafy, branching stems 1.5-2 m. tall.

Leaves:

Leaves alternate, the lower petiolate, becoming subsessile upward; leaf blade oblong-lanceolate to ovate-lanceolate, acuminate, up to 20 cm. long, the base truncate to cordate; stipules sheathing, not lacerate.

Flowers:

Inflorescence an open, terminal panicle; flowers white, perfect; the 5 perianth segments obovate, 3-4 mm. long, not keeled.

Identification Notes:

Achene 3-angled, black, smooth and shining, 3 mm. long.

Accepted Name:
Persicaria wallichii Greuter & Burdet
Publication: Willdenowia. 19: 41. 1989. 1989.

Synonyms & Misapplications:
Aconogonon polystachyum (Wall. ex Meisn.) M. Král
Pleuropteropyrum polystachyum (Wall. ex Meisn.) Munshi & G.N. Javied
Polygonum polystachyum Wall. ex Meisn. [HC]
Reynoutria polystachya (Wall. ex Meisn.) Moldenke
Rubrivena polystachya (Wall. ex Meisn.) M. Král
Infraspecies:
var. wallichii – garden knotweed, Himalayan knotweed
Additional Resources:

PNW Herbaria: Specimen records of Persicaria wallichii in the Consortium of Pacific Northwest Herbaria database.

WA Flora Checklist: Persicaria wallichii checklist entry.

E-Flora BC: Persicaria wallichii atlas page.

CalPhotos: Persicaria wallichii photos.

USDA Plants: Persicaria wallichii information.

23 photographs:
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