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

Polygonum paronychia Cham. & Schltdl.
black knotweed (beach knotweed)
Polygonaceae (Buckwheat family)

Introduction to Vascular Plants

© Jim Riley  Email the photographer   (Photo ID #884)

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Distribution of Polygonum paronychia
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Species Information

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Perennial semi-shrub from a strong, fibrous root; stems prostrate to ascending, several, freely branched, smooth, rooting at the branch nodes, 30-100 cm tall/long.
Basal leaves lacking; stem leaves alternate, narrowly oblong but rolled under and so appearing linear in outline, the blades 1-2 cm long, unstalked; stipules translucent, ragged.
Inflorescence of several flowers in clusters in the upper leaf axils; perianths white to pink, 5-6 mm long, unequally 5-lobed 1/2 to 3/4 the distance to the base.
Achenes, 3-angled, 4-5 mm long, black, smooth, shiny.

Source: The Illustrated Flora of British Columbia

Habitat / Range

Moist to mesic sand dunes and beaches in the lowland zone; infrequent on S Vancouver Island and the Gulf Islands; S to CA.

Source: The Illustrated Flora of British Columbia


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.

Taxonomic and Nomenclatural Links

Additional Photo Sources

General References