Smooth spike-primrose

Boisduvalia campestris Jepson, Fl. W. Calif., 330. 1901; B. glabella (Nuttall) Walpers; B. glabella var. campestris (Jepson) Jepson; B. pygmaea Munz; Epilobium pygmaeum (Munz) Hoch & P. H. Raven; Oenothera glabella Nuttall 1840, not E. glabellum G. Forster 1786

Herbs with 1 or more unbranched taproots. Stems usually suberect, rarely matted, terete, 1.5–50 cm, often with sprawling, decumbent proximal branches, rarely simple, glabrous proximally or throughout, sometimes ± densely strigillose and/or villous distally. Leaves crowded, subsessile, blade lanceolate to narrowly lan­ceolate or oblong, 0.8–3.5 × 0.2–0.6(–1) cm, longer than subtending internodes, base cuneate, margins evenly serrulate, 4–7 teeth per side, lateral veins obscure, 2–5 per side, apex acute, surfaces strigillose and ± villous, at least along veins and margins; bracts not much reduced. Inflorescences erect spikes, congested, unbranched, densely strigillose and ± villous or subglabrous. Flowers erect, often hidden by subtending bracts, often cleistogamous; buds 1.2–2 × 0.7–1.1 mm; floral tube 0.3–1.1 × 0.2–0.8 mm, raised ciliate ring proximal to mouth inside; sepals reddish green, 0.7–1.9 × 0.6–1.2 mm; petals pale pink, fading purplish rose, 0.9–3.5 × 0.7–0.9 mm, apical notch 0.3–1.3 mm; filaments light pink, those of longer stamens 0.5–1.5 mm, those of shorter ones 0.4–0.9 mm; anthers pale yellow, 0.4–0.8 × 0.3–0.5 mm; ovary 3–5 mm, usually densely villous; style pale pink, 0.6–1.8 mm, stigma clavate, irregularly 4-lobed to subentire, 0.5–1 × 0.2–0.6 mm, surrounded by longer anthers. Capsules cylindrical to subfusiform, ± terete, 4.5–8 mm, beak 0.8–1 mm, usually dehiscing on distal 1/3, sometimes tardily splitting to base, central axis prematurely disintegrating, villous; subsessile. Seeds 7–14 per tightly packed row, irregularly angular-fusiform, 1–1.3 × 0.4–0.6 mm, chalazal collar absent, surface irregularly reticulate. 2n = 30.

Flowering May–Sep. Vernally moist flats, depressions, shores, and open fields, usually clay soils; 30–3000 m; Alta., B.C., Sask.; Ariz., Calif., Idaho, Mont., Nev., N.Mex., N.Dak., Oreg., S.Dak., Utah, Wash., Wyo.; Mexico (Baja California); South America (Argentina).

Epilobium campestre is widespread in temperate western North America. Like E. cleistogamum, it also grows in habitats that are only moist early in the growing season, or otherwise ephemeral moist places, like shores of reservoirs with fluctuating water levels(P. H. Raven and D. M. Moore 1965), and consequently flowers earlier than most species of Epilobium.

The occurrence of this species in Chubut Province, Argentina, appears to be the result of natural long-distance dispersal, probably by birds.

Seeds of Epilobium campestre are inclined about 20° from vertical, which while unique and characteristic is a difficult character to observe. Seeds are tightly packed in rigid capsules, as described under E. cleistogamum.

Oenothera pygmaea Spegazzini 1899, an illegitimate name (not Douglas 1832), pertains here.