Herbs with small, 3–6 mm, round or oblong, compact turions 1–5 cm below-ground. Stems strict, erect, terete, 2–50 (–60) cm, rarely branched only in larger plants, subglabrous proximal to inflorescence except for raised strigillose lines decurrent from margins of petioles, or sometimes ± densely long-villous through­out with inconspicuous decurrent lines. Leaves opposite proximally, alternate on inflorescence, subsessile or proximally with petioles 1–1.5 mm; blade ovate proximally to lanceolate or narrowly elliptic distally, 0.5–4.7 × 0.2–1.4 cm, base rounded to cuneate, mar­gins subentire proximally to denticulate distally, 8–20 teeth per side, veins inconspicuous, 3–6 per side, apex obtuse to subacute, surfaces mostly glabrous with strigillose margins; bracts much reduced. Inflorescences usually nodding in bud, erect later, open racemes, sometimes congested, usually mixed strigillose and glandular puberulent, rarely also mixed villous, or rarely subglabrous. Flowers erect; buds 2–5 × 1–2 mm; pedicel 3–8 mm; floral-tube 0.5–1.7 × 0.8–1.6 mm, with slightly raised ring of spreading hairs at mouth inside; sepals green, 1.2–2.8 × 0.5–1 mm, abaxial surface subglabrous or sparsely glandular puberulent; petals white, often fading pink, 1.6–5.5 × 1.2–3 mm, apical notch 0.3–1.2 mm; filaments white or cream, those of longer stamens 0.6–2.5 mm, those of shorter ones 0.4–1.5 mm; anthers cream, 0.2–0.9 × 0.2–0.5 mm; ovary 10–14 mm, strigillose and glandular puberulent or subglabrous; style cream, 0.8–5 mm, stigma clavate, entire, 0.4–1.2 × 0.3–0.7 mm, usually surrounded by, rarely exserted beyond, anthers. Capsules very narrowly cylindrical, (15–) 24–60 mm, surfaces usually subglabrous to mixed strigillose and glandular puberulent, rarely sparsely villous; pedicel 8–40 mm. Seeds narrowly fusiform to narrowly obovoid, 1.1–1.6 × 0.4–0.6 mm, chalazal collar ± conspicuous, 0.05–0.2 mm, light-brown, surface papillose; coma easily detached, white, 3–6 mm. 2n = 36.

Phenology: Flowering Jun–Sep.
Habitat: Semi-shaded stream banks, wet grassy slopes or meadows, bogs, seasonally wet sites, vernal pools.
Elevation: 100–3700 m.

Distribution

• Generated Map
• Legacy Map

Alta., B.C., Sask., Ariz., Calif., Colo., Idaho, Mont., Nev., N.Mex., Oreg., S.Dak., Utah, Wash., Wyo.

Discussion

Epilobium hallianum has condensed fleshy turions and generally strict habit, suggesting an affinity with E. ciliatum or E. saximontanum, both with the AA arrangement. However, E. hallianum has the BB arrangement (S. R. Seavey and P. H. Raven 1978) and apparently more distant relationship to those other species.

In different parts of its geographical range Epilobium hallianum shows considerable morpho­logical variability, especially in leaf shape and margins, and in type and pattern of stem vestiture, including plants in the southern part of its range with densely villous stems that have been treated as E. ursinum. In part because of this variability and in part because the very characteristic condensed turions are easily lost during collection and/or often overlooked, E. hallianum is frequently misidentified.

Selected References

None.

Lower Taxa

None.