This is a rhizomatousperennial herb producing one or more erect stems reaching a maximum height of about 60 centimetres (2 feet).[3] It has two to four pairs of leaves on the stem, each on a long petiole. The leaves are heart-shaped to arrowhead-shaped and finely toothed along the edges. The inflorescence bears one or more daisylike flower heads 5–9 cm (2–3+1⁄2 inches) in width,[3] lined with white-haired phyllaries and sometimes studded with resin glands. The center of each head contains golden yellow disc florets and a fringe of 10–15 bright golden ray florets approaching 3 cm (1+1⁄4 in) in maximum length.[3][4][5][6][7] The flowers usually bloom from April to June, but sometimes do so as late as September.[3]
The fruit is a hairy achene up to 1 cm (1⁄2 in) long, not counting its off-white pappus. Seeds are dispersed on the wind. An individual plant can live 12 years, surviving periodic wildfire by resprouting from its long, slender rhizome afterward.[7][8]
The species could be confused with the similar Arnica latifolia, from which it can be distinguished by the leaves. The leaves of A.cordifolia are larger and heart-shaped.[9]
^Klinkenberg, Brian, ed. (2017). "Arnica cordifolia". E-Flora BC: Electronic Atlas of the Plants of British Columbia [eflora.bc.ca]. Lab for Advanced Spatial Analysis, Department of Geography, University of British Columbia, Vancouver. Retrieved 2019-09-15.
^Giblin, David, ed. (2018). "Arnica cordifolia". WTU Herbarium Image Collection. Burke Museum, University of Washington. Retrieved 2019-09-15.
^"Arnica cordifolia". in Jepson Flora Project (eds.) Jepson eFlora. Jepson Herbarium; University of California, Berkeley. 2018. Retrieved 2019-09-15.