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

Epilobium palustre L.
swamp willowherb (marsh willowherb)
Onagraceae (Evening Primrose family)

Introduction to Vascular Plants

© Jamie Fenneman  Email the photographer   (Photo ID #17159)

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Distribution of Epilobium palustre
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Species Information

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Perennial herb from a slender rhizome, stolons threadlike, with some leaves, tipped with compact, fleshy bulblets; stems erect, 5-80 cm tall, simple or branched, short stiff-hairy in lines below, stiff-hairy above.
Mostly opposite, nearly linear to lanceolate or narrowly oblong, 1.5-7 cm long, 0.2-1.9 cm wide, blunt, entire or slightly toothed, glabrous except margins and veins short stiff-hairy; unstalked or nearly so.
Inflorescence loosely racemose to paniculate, densely short stiff-hairy, nodding to erect in bud; hypanthium 0.6-1.8 mm long; petals 2-9 mm long, white to pinkish, notched; sepals 1.4-4.5 mm long, short stiff-hairy; anthers 0.4-1 mm long; ovaries 1.4-3 cm long, densely short stiff-hairy; styles 1-4.5 mm long; stigmas cylindric to club-shaped.
Capsules, linear, 3-9 cm long, short stiff-hairy; stalks slender, 1.5-6 cm long; seeds 1.4-2.2 mm long, pimply, tuft of hairs white to tawny, 5-7 mm long, persisting.

Source: The Illustrated Flora of British Columbia

Habitat / Range

Bogs, fens, swamps and moist streambanks in the steppe and montane zones; frequent in C and N BC; circumpolar, N to AK, YT and NT, E to NF, and S to NY, WI, CO and CA; Eurasia.

Source: The Illustrated Flora of British Columbia


Ecological Framework for Epilobium palustre

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) 83 1013 2091
Slope Gradient (%) 0 2 60
Aspect (degrees)
[0 - N; 90 - E; 180 - S; 270 - W]
10 183 266
Soil Moisture Regime (SMR)
[0 - very xeric; 4 - mesic;
8 - hydric]
2 6 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: BWBS(5), CWH(4), ESSF(13), ICH(6), IDF(19), MH(1), MS(8), SBPS(13), SBS(32)


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 montane boreal & cool temperate.

Synonyms and Alternate Names

Epilobium lineare Muhl.
Epilobium oliganthum Michx.
Epilobium palustre var. grammadophyllum Hausskn.
Epilobium palustre var. labradoricum Hausskn.
Epilobium palustre var. lapponicum Wahlenb.
Epilobium palustre var. longirameum Fern. & Wieg.
Epilobium palustre var. oliganthum (Michx.) Fern.
Epilobium pylaieanum Fern.
Epilobium wyomingense A. Nels.

Taxonomic and Nomenclatural Links

Additional Photo Sources

General References