Arnica cernua is a species of arnica known by the common name serpentine arnica. It is native to the Klamath Mountains of northern California and southern Oregon, where it is a member of the serpentine soils flora.

This is a perennial herb growing one or more green to purplish stems up to about 30 centimeters tall. There are 3 or 4 pairs of leaves on long petioles. The blade is oval to spade-shaped and may be several centimeters long. The inflorescence contains one or more hairy, glandular, daisylike flower heads, each with a center of yellowish disc florets and a fringe of yellow ray florets which approach 3 centimeters in maximum length.

The fruit is a cylindrical achene about 7 millimeters long which is covered in stiff hairs and has a white pappus at one end.

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