This photograph is from several summers ago. I hope I’ve identified the plant correctly. Arnica latifolia is commonly known as mountain arnica or broadleaf arnica. It is widely distributed in western North America from Alaska to northern California and east as far as Wyoming and Colorado. As one common name implies, it is generally a species of mid- to high-elevations. Habitats where it can be found vary, ranging from forests to rocky slopes to meadows.
Identification of Arnica latifolia can be problematic, as plants can be similar in appearance to Arnica cordifolia. The latter species, though, has pubescent leaves and achenes, larger capitula (flower heads) and a tendency to grow as single plants. Complicating the matter of identification even more is that the two species hybridize, and, to quote the Illustrated Flora of British Columbia, “numerous intermediates may be encountered”.
Digging a little deeper thanks to the late Dr. Gerald Straley’s 1980 Ph.D. thesis, Systematics of Arnica, Straley asserts that Arnica latifolia likely evolved from Arnica cordifolia, and, “The close relationship of these two species can be seen in numerous populations which combine many of the morphological characters of both species”. In turn, Straley also notes that Arnica latifolia is likely the progenitor species of the serpentine endemic Arnica cernua and perhaps a hybrid parent of the subalpine-alpine Arnica gracilis.
Something else I will have to keep in mind for future identifications in the field thanks to Dr. Straley is that Arnica cordifolia has leaves that are distinctly fragrant when bruised, compared with little to no fragrance in Arnica latifolia (now I have to wait until next summer to try this…).