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

Epilobium torreyi (S. Watson) Hoch & P.H. Raven
brook spike-primrose (Torrey's willowherb)
Onagraceae (Evening Primrose family)

Introduction to Vascular Plants

© Norman Jensen  Email the photographer   (Photo ID #8379)

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Distribution of Epilobium torreyi
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This tiny June-flowering species occurs in seasonally wet shallow depressions (vernal pools and associated habitats) from southwest British Columbia to northwest California, including Idaho and Nevada. In BC, it is known from two sites on southern Vancouver Island. It is a habitat specialist with strict growing requirements as is typical of vernal pool species. Rainfall and groundwater provide moisture requirements, and nutrient levels are low at these sites. Seeds germinate following submersion in winter and spring, however dispersal capabilities of the species are low.

No plants of this species have been observed at the two known sites since 1966 and 1993 respectively, and the species is potentially extirpated from BC. It is possible that the seed bank for this species persists and that restoration work at the sites might provide a way to rescue the species where invasive species might be influencing persistence. However, water deficits in regional groundwater recharge were observed during climate data analysis and may have contributed to population loss and invasions at these sites.

Read the COSEWIC status report for this species.

Species Information

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Annual herb from a taproot; stems ascending to erect, 10-60 cm tall, usually branched from base, peeling below; plants greyish spreading-hairy.
Opposite only near base, linear or narrowly lanceolate, reduced above, entire or remotely fine-toothed, hairy but glabrous near base; nearly stalkless.
Inflorescence loose to somewhat crowded in leafy, terminal spikes, glandular, flower-leaves similar to others but entire and smaller; flowers generally fertilized in the bud, not opening; hypanthium 0.4-1 mm long; petals 1-3 mm long, pink or white; sepals 0.7-2 mm long; stigmas rarely 4-lobed.
Capsules, cylindric, about 8-13 mm long, flexible, curved near tip, long-hairy, short-beaked, 4-chambered; valves adhering to partitions, the axis breaking-up as seeds shed; seeds 6-8 per chamber, 1-1.5 mm long, netted, glabrous, without a tuft of hairs.

Source: The Illustrated Flora of British Columbia

Habitat / Range

Moist grasslands and open slopes in the lowland zone; rare on SE Vancouver Island; S to ID, NV and CA.

Source: The Illustrated Flora of British Columbia

Additional Notes


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 stricta (A. Gray) Greene
Gayophytum strictum A. Gray

Taxonomic and Nomenclatural Links

Additional Photo Sources

Species References

COSEWIC 2006. COSEWIC assessment and status report on the brook spike-primrose Epilobium torreyi in Canada. Committee on the Status of Endangered Wildlife in Canada. Ottawa.

Klinkenberg, Brian and Rose Klinkenberg. 2007. Draft National Recovery Strategy for Brook Spike-primrose (Epilobium torreyi) in Canada. Parks Canada, Victoria.

General References