Arnica angustifolia is a member of the aster family (Asteraceae) with upright, showy yellow flowering heads and narrow leaves. This perennial forb grows from a rhizome, reaching up to 40 cm tall, found in floodplains, rocky slopes, and tundra on warmer slopes. The basal leaves are narrowly lanceolate and petiolate, simple, with entire margins, more or less densely hairy. The stems leaves are similar to basal leaves, oppositely arranged in 2-4 pairs, becoming smaller upwards. Stalks are densely white hairy. Plants are usually unbranched, with a single flowering head per stem, sometimes several. The involucres are 10-18-mm long. The ray and tube flowers are yellow, the rays (petals) are oblong and toothed at the apex. In fruit, the flowering head holds many narrow achenes (dry fruit), each topped with a tuft of white hairs, the pappus. Arnica angustifolia is distinguished from the other arnica species in the park by its narrow basal leaves, upright flowering heads and white pappus.
Arnica angustifolia typically flowers from June to August, depending on aspect and elevation.
Plants are monoecious. The showy flowers are visited by a variety of insects (Kevan 1972), but whether they are self-compatible or strictly outcrossed is unknown. Seeds have an attached parachute of hairs, aiding in wind-dispersal.
The Gwich'in people traditionally used arnica flowers to make tea for stomach ailments (Andre and Fehr 2000 in Aiken et al. 2003). This traditional use is contraindicated by current research on the commonly used European Arnica montana which has demonstrated side effects (such as burning of the internal mucosa) from internal use (Blumenthal 2000, Moore 1993).
Arnica angustifolia has a circumpolar, arctic-alpine distribution occurring across Canada and as far south as Colorado in the Rocky Mountains. This species occurs widely on tundra and open woodlands in Alaska. Narrowleaf arnica occurs primarily north of the Alaska Range and east of the McKinley River in Denali (except for one locality south of the Alaska Range on the Yentna River in the southwest corner of the park).
Narrowleaf arnica is common on south-facing slopes in Denali where it occurs at 200-1100 m on flat to steep inclines. Where it occurs on north-facing slopes the inclines are greater than 20 degrees. It is found most frequently from 900-1100 m in the sub-alpine and alpine life zones.