Species: Epilobium pygmaeum (Speg.) Hoch & Raven

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Epilobium pygmaeum (Speg.) Hoch & Raven

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TAXONOMY

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

DISTRIBUTION

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

HABITAT

Saskatchewan:

moist to drying, bare, clayey mudflats in prairie and field depressions, slough bottoms, and shores

RARITY STATUS

Provincial Status According
to Harms (2003):

Vulnerable

Nature Conservancy Status:

G5 N2 S2

Saskatchewan Species at
Risk Status:

None

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.

SPECIES DESCRIPTION

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

EPILOBIUM KEY FOR SPECIES FOUND IN SASKATCHEWAN

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

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

3 Plants with thread-like, somewhat leafy runners with overwintering shoots; inflorescence white-hairy; stem leaves often inrolled	4
3 Plants without runner; inflorescences glandular hairy or hairless; stem leaves never inrolled	5

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

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