Arnica louiseana

Plants 5-20 cm. Stems simple. Leaves 1-3 pairs, mostly cauline (shorter plants often with leaves crowed mostly toward bases); petiolate; blades elliptic, oblong, or ovate-lanceolate, 1.5-7.5 × 0.5-2 cm, margins usually entire, rarely denticulate or slightly undulate, apices usually obtuse, sometimes acute or acuminate, faces glabrous or hispidulous-puberulent, ± densely stipitate-glandular. Heads usually 1, sometimes 2-3 (nodding at flowering). Involucres campanulate-turbinate. Phyllaries 10-20, narrowly lanceolate (stipitate-glandular). Ray florets 7-10; corollas yellow. Disc florets: corollas yellow; anthers yellow. Cypselae brown, 3-5 mm, abaxially glabrous, adaxially sparsely hirsute or glabrous throughout, usually stipitate-glandular toward apices, sometimes densely stipitate-glandular throughout; pappi white, bristles barbellate. 2n = 76, 95.

Flowering Jul-Aug. Exposed tundra slopes and calcareous rock slides; 1800-2100 m; Alta., B.C.