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

Epilobium densiflorum (Lindl.) Hoch & P.H. Raven
dense spike-primrose (denseflower willowherb)
Onagraceae (Evening Primrose family)

Introduction to Vascular Plants

© Adolf Ceska  Email the photographer   (Photo ID #11084)

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Distribution of Epilobium densiflorum
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Species Information

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Annual herb from a taproot; stems 15-100 cm tall, simple or branched above, peeling below; plant densely white-hairy to long soft- or stiff-hairy, sometimes glandular.
Alternate, except near base, lanceolate, becoming narrowly egg-shaped in the inflorescence,1-8.5 cm long, entire or remotely fine-toothed, upper ones hairy; unstalked or nearly so.
Inflorescence of crowded, densely-leafy, terminal and lateral spikes; hypanthium 1.5-4 mm long; petals 3-10 mm long, white to rose-purple, notched at tip; sepals 2-9 mm long; stigmas irregularly 4-lobed.
Capsules, more or less spindle-shaped, long-hairy, 0.4-1.1 cm long, very short-beaked, 4-chambered; valves split free of partition, the partition adhering to axis; seeds 3-6 per chamber, flattened, 1.2-2 mm long, netted, glabrous, brown, without tuft of hairs.

Source: The Illustrated Flora of British Columbia

Habitat / Range

Moist to dry meadows, roadsides and waste areas in the lowland zone; rare on S Vancouver Island; E to AB and S to MT, ID, NV, CA and MX.

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.

Synonyms and Alternate Names

Boisduvalia densiflora (Lindl.) S. Watson
Boisduvalia densiflora var. pallescens Suksd.
Boisduvalia densiflora var. salicina (Nutt. ex Torr. & A. Gray) Munz
Boisduvalia salicina (Nutt. ex Torr. & A. Gray) Rydb.
Oenothera densiflora Lindl.

Taxonomic and Nomenclatural Links

Additional Photo Sources

General References