Epilobium affine Bongard var. fastigiatum Nuttall in J. Torrey and A. Gray, Fl. N. Amer. 1: 489. 1840; E. concinnum Congdon; E. fastigiatum (Nuttall) Piper; E. glaberrimum var. fastigiatum (Nuttall) Trelease ex Jepson; E. glaberrimum var. latifolium Barbey; E. platyphyllum Rydberg

Stems 5–35 cm, sometimes sparsely strigillose and glandular puberulent distally, rarely with faint raised strigillose lines decurrent from margins of distal petioles. Leaf blades usually blue-green, lanceolate to narrowly ovate or elliptic, (0.5–)1–3.4 × (0.3–)0.7–1.8 cm, length/width ratio less than 4. Flowers: floral tube 0.9–1.4 × 1–2.2 mm; sepals 2.5–5.2 × 0.8–1.6 mm; petals rose-purple to pink, 3.4–8 × 1.8–3.9 mm; filaments of longer stamens 2.4–5 mm, those of shorter ones 1.6–3 mm; ovary 10–34 mm, style 2.2–3.6 mm. Capsules 15–45(–55) mm. 2n = 36.

Flowering Jun–Sep. Rocky, well drained soil, moist alpine slopes, seepage, talus slope, stream banks, bogs, mainly upper montane to alpine; (1000–)1200–3500 m; Alta., B.C.; Calif., Idaho, Mont., Nev., Oreg., Utah, Wash., Wyo.

Subspecies fastigiatum occurs primarily along the Sierra Nevada-Cascade axis, but also ranges through the Basin Ranges to the Rocky Mountains from northern Wyoming to southern Alberta and British Columbia.