Arnica chamissonis

Plants 20-80(-150) cm. Stems usually branched from mid heights or distally. Leaves 4-10 pairs, mostly cauline (evenly distributed; basal leaves often withered by flowering, 1-2 pairs, subsessile to short-petiolate); sessile (proximalmost with membranous connate-sheathing bases); blades lance-elliptic, broadly oblanceolate, or oblong, 5-20 × 2-6(-8) cm, margins entire or remotely denticulate to prominently dentate, apices acute, faces nearly glabrous or puberulent to sparsely or densely white-tomentose-pilose. Heads (1-)3-10(-16). Involucres campanulate (rarely hemispheric). Phyllaries 8-23, nearly linear to narrowly lanceolate (apices each with conspicuous tuft of white hairs). Ray florets 8-20; corollas yellow. Disc florets: corollas yellow; anthers yellow. Cypselae gray to brown, 3-8 mm, subglabrous to sparsely hirsutulous, stipitate-glandular; pappi stramineous, bristles barbellate to subplumose. 2n = 38, 57, 76.

Flowering Apr-Sep. Moist meadows and conifer forests, stream banks, late snow-melt areas, often montane to subalpine; 0-3500 m; Alta., B.C., Man., N.W.T., Ont., Que., Sask., Yukon; Alaska, Ariz., Calif., Colo., Idaho, Mont., Nev., N.Mex., Oreg., Utah, Wash., Wyo.