Epilobium glaberrimum

Barbey in W. H. Brewer et al.

Bot. California 1: 220. 1876.

Common names: Glaucous willowherb
Synonyms: Epilobium fastigiatum var. glaberrimum (Barbey) Piper
Treatment appears in FNA Volume 10.

Herbs with branching, wiry basal shoots with crowded, often dark, scales. Stems many, erect or ascending, often densely clumped, slender, terete, 5–75(–85) cm, simple or dis­tally branched, glabrous and glaucous, sometimes strigillose and/or mixed glandular puberulent distally, rarely with faint raised strigillose lines decurrent from margins of distal petioles. Leaves opposite and crowded proximal to inflorescence, alternate and widely spaced distally, subsessile and ± clasping; blade light green or blue-green, very narrowly lanceolate to narrowly ovate or elliptic, (0.5–)1–7.2 × (0.3–)0.5–1.8 cm, base cuneate, margins subentire or faintly denticulate, 8–15 teeth per side, veins inconspicuous, 3–6 per side, apex obtuse proximally to acute distally, glabrous and glaucous; bracts much reduced and narrower. Inflorescences erect racemes, glabrous or ± sparsely glandular puberulent, sometimes mixed strigillose. Flowers erect; buds 2.5–5 × 2–3.5 mm; pedicel 2–11(–20) mm; floral tube 0.7–2.3 × 1–2.5 mm, ring of spreading hairs at mouth inside or without a ring; sepals often red-tipped, sometimes keeled, 2.5–7.5 × 0.8–2 mm, abaxial surface glabrous or strigillose and/or glandular puberulent; petals usually light pink to rose-purple, rarely white, 3.4–10(–12) × 1.8–5 mm, apical notch 0.5–3 mm; filaments purple to white or cream, those of longer stamens 2.4–5(–6) mm, those of shorter ones 1.4–4 mm; anthers light yellow, 0.5–1.2(–1.5) × 0.3–0.7 mm; ovary 10–42 mm, subglabrous to sparsely mixed strigillose and glandular puberulent; style light yellow or cream, 1.7–5(–7) mm, stigma clavate to subcapitate, 0.8–3 × 0.5–1.2 mm, usually surrounded by, rarely exserted beyond, longer anthers. Capsules 15–75 mm, with small protuberance at base, surfaces subglabrous to sparsely mixed strigillose and glandular puberulent; pedicel 5–18(–25) mm. Seeds narrowly obovoid, 0.7–1(–1.3) × 0.3–0.5 mm, chalazal collar inconspicuous, light brown or gray, surface coarsely papillose in longitudinal rows; coma readily detached, white, 4–9 mm.


w North America, nw Mexico.


Subspecies 2 (2 in the flora).

Epilobium glaberrimum is restricted mainly to the Sierra Nevada-Cascade region, but also (subsp. fastigiatum) in the northern Rocky Mountains. It is one of the more easily identified species due to its consistently glabrous and glaucous aspect. Although the distributions and elevational ranges of the two subspecies appear to overlap extensively, they are largely allopatric with subsp. glaberrimum occurring in lower to mid montane zones and subsp. fastigiatum in upper montane to subalpine zones in the southern part of its range, and in lower zones farther north.

Selected References



1 Stems 20–75(–85) cm; leaf blades (2–)3–7.2 cm, very narrowly lanceolate to lanceolate or narrowly elliptic (length/width ratio more than 4); capsules 45–75 mm; petals (4–)5–10(–12) mm. Epilobium glaberrimum subsp. glaberrimum
1 Stems 5–35 cm; leaf blades (0.5–)1–3.4 cm, lanceolate to narrowly ovate or elliptic (length/width ratio less than 4); capsules 15–45(–55) mm; petals 3.4–8 mm. Epilobium glaberrimum subsp. fastigiatum