Snow arnica

Arnica louiseana Farr subsp. griscomii (Fernald) Maguire

Plants 5–40 cm. Stems usually simple, rarely branched. Leaves 1–4 pairs, mostly cauline; petio-late; blades elliptic, lanceolate, oblanceolate, ovate, or spatulate, 1.2–10 × 0.5–3.5 cm, margins usually denticulate to dentate, rarely entire, apices acute to obtuse or abruptly pointed, faces usually glabrous or sparingly hispidulous-puberulent, rarely stipitate-glandular. Heads usually 1, sometimes 2–3 (erect or nodding). Involucres hemi-spheric to campanulate-turbinate (bases sparsely to densely pilose, hairs white or yellow). Phyllaries 9–20, lanceolate to oblanceolate, not stipitate-glandular. Ray florets 6–17; corollas yellow. Disc florets: corollas yellow; anthers yellow. Cypselae brown, 2.5–6 mm, abaxially glabrous, adaxially sparsely hirsute or glabrous throughout, rarely glandular; pappi white, bristles barbellate.

Subspecies 2 (2 in the flora): North America; Asia (e Russia).