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

Polygonum majus (Meisn.) Piper
wiry knotweed
Polygonaceae (Buckwheat family)

Introduction to Vascular Plants

© Jim Riley  Email the photographer   (Photo ID #23133)

E-Flora BC Static Map
Distribution of Polygonum majus
Click here to view the full interactive map and legend
Details about map content are available here
Click on the map dots to view record details.

Species Information

Click on the image below to view an expanded illustration for this species.

Annual herb from a small taproot; stems ascending to erect, numerous, simple to freely branched, 10-40 cm tall.
Basal leaves lacking; stem leaves alternate, linear to narrowly oblong, egg-shaped or elliptic, the blades 1-8 cm long, unstalked or nearly so, sometimes reduced to bracts above; stipules short-sheathing, 5-12 mm long, clear, becoming ragged.
Inflorescence of few flowers in elongate axillary racemes; perianths 1.5-5 mm long, greenish with white or pinkish margins, 5-lobed nearly to the base.
Achenes, lanceolate to egg-shaped, sometimes 3-angled, black, smooth and shiny, 2-4 mm long.

Source: The Illustrated Flora of British Columbia

Habitat / Range

Dry grasslands, shrublands, rocky slopes and forest openings in the steppe and montane zones; infrequent in SC BC; S to ID, W MT and CA.

Source: The Illustrated Flora of British Columbia


Ecological Framework for Polygonum majus

The table below shows the species-specific information calculated from
original data (BEC database) provided by the BC Ministry of Forests and Range.
(Updated August, 2013)

Site Information
Value / Class




Elevation (metres) 350 691 1180
Slope Gradient (%) 4 30 70
Aspect (degrees)
[0 - N; 90 - E; 180 - S; 270 - W]
20 198 334
Soil Moisture Regime (SMR)
[0 - very xeric; 4 - mesic;
8 - hydric]
1 2 5
Modal Nutrient Regime
Number of field plots
 species was recorded in:
Modal BEC Zone Class
All BEC Zones (# of stations/zone) species was recorded in: BG(7), ICH(1), IDF(5), PP(13)


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

Polygonum coarctatum var. majus Meisn.
Polygonum douglasii subsp. majus (Meisn.) J.C. Hickman

Taxonomic and Nomenclatural Links

Additional Photo Sources

Related Databases

General References