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

Persicaria lapathifolia (L.) S.F. Gray
willow weed
Polygonaceae (Buckwheat family)

Introduction to Vascular Plants

© Jamie Fenneman  Email the photographer   (Photo ID #6962)

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Distribution of Persicaria lapathifolia
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Willow weed is a plant species that is variable in appearance and may be both native and introduced. "Persicaria lapathifolia is a morphologically variable complex with more than two-dozen infraspecific taxa described in the New World and Old World." (Hinst and Freeman 2012).

Species Information

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Annual herb from a taproot; stems erect (occasionally prostrate), solitary, usually freely branched, 20-80 cm tall/long.
Basal leaves lacking; stem leaves alternate, lanceolate or oblong-lanceolate, smooth or more often hairy or glandular below, the blades 5-20 cm long, the stalks short; stipules 5-20 mm long, brownish, more or less smooth, fringed with bristly hairs at the top.
Inflorescence a loose, often drooping panicle of spikelike racemes, 1-6 cm long; perianths greenish-white to pink, distinctly veined, the veins branching and turned back at the tip, about 2.5 mm long, 4- to 5-lobed nearly to the base.
Achenes, usually lens-shaped, egg-shaped to nearly rounded, dark brown, smooth and shiny, 2-3 mm long.

Source: The Illustrated Flora of British Columbia

Habitat / Range

Moist meadows and wet shorelines and swamps in the lowland, steppe and montane zones; common in SW BC, infrequent in SC BC, rare in SE and NE BC; introduced from Europe.

Source: The Illustrated Flora of British Columbia


Ecological Framework for Persicaria lapathifolia

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) 885 885 885
Slope Gradient (%) 0 0 0
Aspect (degrees)
[0 - N; 90 - E; 180 - S; 270 - W]
Soil Moisture Regime (SMR)
[0 - very xeric; 4 - mesic;
8 - hydric]
8 8 8
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: SBS(1)


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 lapathifolium L.
Polygonum scabrum

Taxonomic and Nomenclatural Links

Additional Photo Sources

General References