Arnica sororia is a North American species of flowering plant known by the common name twin arnica.[1] It is native to Western Canada (British Columbia, Alberta, Saskatchewan) and the Western United States (Washington, Oregon, California, Nevada, Utah, Idaho, Montana, Wyoming, South Dakota).[2] It grows in grasslands and in conifer forests,[3] as well as the sagebrush steppe.[4]
Arnica sororia is a rhizomatous perennial herb producing one or more hairy, glandular stems NaNcm (-2,147,483,648inches) tall. There are a few to several pairs of broadly lance-shaped leaves along the stem, the lower ones borne on petioles. Leaves may reach up to 14 cm long.[5]
The inflorescence consists of a daisy-like flower head, rarely more than one per stem. These are lined with phyllaries coated in glandular hairs. The flower head has a center of glandular yellow disc florets and a fringe of yellow ray florets. The fruit is an achene a few millimeters long with a white pappus.[5]
