Page authors: Don Knoke, David Giblin
Polygonum majus
Palouse knotweed, wiry knotweed
WTU specimens
Other herbaria

Distribution: Occurring east of the Cascades crest in Washington; British Columbia south to California, east to the Rocky Mountains.

Habitat: Dry, often semi-barren, gravelly to heavy soil, sagebrush desert to lower mountains.

Flowers: May-August

Origin: Native

Conservation Status: Not of concern

Description:
General:

Erect annual, the stem strongly angled, simple or freely-branched, 1-3 dm. tall.

Leaves:

Leaves alternate, numerous, gradually reduced upward, the lower leaves linear to oblong, sessile, 2-5 cm. long and 2-7 mm. wide, jointed at the base; stipules 10-15 mm. long, lacerate.

Flowers:

Flowers mostly paired in open elongate racemes, in the axils of reduced bracts or the lowest in leaf axils, the pedicles slender, reflexed; the 5 perianth segments 4-5 mm. long, attached 1/5 their length, with a greenish midvein and white to pink margins, obtuse; stamens 8, anthers purple; styles 3, short.

Identification Notes:

Achene 3-angled, 3.5-4 mm. long and ½ as wide, smooth, black and shining, tapered at each end.

Accepted Name:
Polygonum majus (Meisn.) Piper
Publication: Fl. Palouse Reg. 63. 1901. 1901.

Synonyms & Misapplications:
Polygonum coarctatum Douglas ex Meisn. var. majus Meisn.
Polygonum douglasii Greene ssp. majus (Meisn.) J.C. Hickman [JPM, ILBC4]
Additional Resources:

PNW Herbaria: Specimen records of Polygonum majus in the Consortium of Pacific Northwest Herbaria database.

WA Flora Checklist: Polygonum majus checklist entry.

E-Flora BC: Polygonum majus atlas page.

CalPhotos: Polygonum majus photos.

USDA Plants: Polygonum majus information.

14 photographs:
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