Arnica cordifolia is a perennial herbaceous plant native to western North America, commonly known as Heartleaf Arnica or Mountain Arnica. It belongs to the genus ''Arnica'' within the family Asteraceae (sunflower family).
Description
''Arnica cordifolia'' typically grows 20 to 60 centimeters (8 to 24 inches) tall from a creeping rhizome. The most distinctive feature of the plant is its basal leaves, which are prominently heart-shaped (cordate), giving the species its epithet ''cordifolia''. These leaves are usually opposite, toothed, and somewhat hairy. The stems are generally hairy and unbranched or sparingly branched, bearing one to several flower heads. The flowers are bright yellow, daisy-like, with 10-20 ray florets and numerous disk florets, blooming from late spring to mid-summer. The fruits are achenes, often with a pappus of white bristles.Distribution and Habitat
This species is widely distributed across western North America, ranging from Alaska and western Canada south through the Rocky Mountains to California, Arizona, and New Mexico. It thrives in a variety of habitats, including moist to dry forests, open woodlands, clearings, and subalpine meadows. It is often found growing in coniferous forests, particularly under conditions of moderate shade.Ethnobotany and Medicinal Uses
Historically, various indigenous peoples of North America utilized ''Arnica cordifolia'' for a range of medicinal purposes. Applications were primarily topical, with poultices or infusions made from the leaves and roots applied to treat bruises, sprains, muscle soreness, arthritis, and skin irritations. Internally, it was sometimes used as an analgesic, for fevers, or coughs, though such uses require caution due to the plant's toxicity.In modern herbal medicine and homeopathy, ''Arnica montana'' is the more widely recognized species. However, ''Arnica cordifolia'' contains similar active compounds, primarily sesquiterpene lactones (such as helenalin), which are responsible for its anti-inflammatory and pain-relieving properties. Due to potential toxicity, especially when ingested, commercial use of ''Arnica cordifolia'' is less common than ''Arnica montana'', and internal use is generally discouraged without expert guidance.