Arnica discoidea is a species of arnica known by the common name rayless arnica. It is native to the woodlands, forests, and chaparral of the western United States. This is a rhizomatous perennial herb producing a hairy, hairy stem 20 to 60 centimeters tall. There are several pairs of toothed oval to spade-shaped leaves on long petioles around the lower half of the stem. The flower cluster contains a few to many flower heads which are coated with hairy hairs. Each head contains only disc florets, but some of the florets around the edge can be expanded and resemble ray florets, making identification of the plant by its flower difficult. The fruit is an achene about 7 millimeters long, not counting its light-colored pappus.