Arnica longifolia

Plants 30-60(-110) cm. Stems (often relatively numerous, clustered in clonal patches) simple. Leaves 5-7 pairs, mostly cauline (basal leaves usually withered by flowering); sessile or subsessile (proximalmost with connate-sheathing bases); blades lanceolate to lance-elliptic, 5-12(-15) × 1.5-3.5 cm, margins usually entire, rarely denticulate, apices acute to acuminate, faces scabrid-puberulent, sometimes glandular (distal leaves not much reduced). Heads 3-20(-35). Involucres turbinate-campanulate. Phyllaries 11-15(-20), narrow to broadly lanceolate. Ray florets 6-15; corollas yellow. Disc florets 6-11; corollas yellow; anthers yellow. Cypselae brown to black, 3-7 mm, glabrous or sparsely hirsutulous, stipitate-glandular; pappi stramineous to tawny, bristles barbellate to subplumose. 2n = 57, 76.

Flowering Jun-Oct. Montane coniferous forests to alpine, usually moist areas, stream banks or late snow-melt areas; 1300-3700 m; Alta., B.C.; Calif., Colo., Idaho, Mont., Nev., Oreg., Utah, Wash., Wyo.