Epilobium pygmaeum (Speg.) Hoch & Raven
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Family: Onagraceae
Genus: Epilobium pygmaeum
Species Synonyms: Boisduvalia glabella (Nutt.) Walt.
Boisduvalia glabella var. campestris (Jepson) Jepson
Boisduvalia pygmaea (Speg.) Munz
Oenothera glabella Nutt.
Common Names: smooth willoweed
smooth boisduvalia
smooth spike-primrose
Canada: south-central British Columbia, southeastern Alberta – south-central Saskatchewan
Saskatchewan: southwestern – south-central Saskatchewan; Leader – Cypress Hills – Val Marie, Wood Mountain – Mortlach
Ecoregion: Cypress Upland, Mixed Grassland, Moist Mixed Grassland
Saskatchewan: moist to drying, bare, clayey mudflats in prairie and field depressions, slough bottoms, and shores
Provincial Status According
to Harms (2003):
Nature Conservancy Status: G5 N2 S2
Saskatchewan Species at
Risk Status:
COSEWIC Status: None
Smooth willoweed is vulnerable because it is rare or uncommon in Saskatchewan. It is only somewhat regionally restricted extending to a limited extent into adjacent general regions of the province. Most local populations are small. Possible threats have been identified for this species.
Height: 10 – 30 cm
Roots: taproot
Stems: annual, creeping and spreading, often branching near the base, hairless to hairy
Leaves: alternate, sessile, 10 – 20 mm long, lance-shaped to oval, margin square-toothed to entire
Inflorescence: spikes leafy, terminal, flowers crowded
Flowers: inconspicuous; sepals 4, green; petals 4, < 3 mm long, purple or violet; pollen in tetrads; stigma head-like
Fruits: capsule 6 – 8 mm long, 4-ribbed, pointed but not beaked; seeds many
1 Seeds without a tuft of hairs at the tip; leaves always alternate; plants annual, in seasonally moist areas which are dry at time of flowering
E. pygmaeum
1 Seeds with a tuft of hairs at the tip; leaves alternate or opposite; plants annual or perennial, in permanently moist areas which are moist at time of flowering
2 Plants annual, with a taproot; epidermis on lower stem exfoliating; tuft of hairs on seeds pale yellow, deciduous
E. brachycarpum
2 Plants perennial, often with small orverwintering shoots or runners; epidermis not exfoliating; tuft of hairs on seeds whitish, persistent
3 Plants with thread-like, somewhat leafy runners with overwintering shoots; inflorescence white-hairy; stem leaves often inrolled
3 Plants without runner; inflorescences glandular hairy or hairless; stem leaves never inrolled
4 Leaves linear to lance-shaped; inflorescence without glands; flowers nodding in bud
E. palustre
4 Leaves linear; inflorescence with glandular and other hairs; flowers erect
E. leptophyllum
5 Plants to 60 cm high, not forming rosettes
E. halleanum
5 Plants to 190 cm high, forming rosettes
6 Stem leaves narrowly lance-shaped to ovate; inflorescence not leafy, branched; petals white to pink
E. ciliatum ssp. ciliatum
6 Stems leaves broader; inflorescence leafy, unbranched; petals pink to purple
E. ciliatum spp. glandulosum