The crowded leaves of hymenoxys cooperi
are concentrated around the base and lower stem, and are divided into an odd number of narrow, linear, well-separated lobes, The lower stems and lower leaf stalks are red to purple in color, and all surfaces have a covering of short glandular hairs. Plants usually have just one stem, or up to three, between 2 and 3 feet tall.
A small number of flowerheads are produced towards the top of the stems, in an open cluster. Each flower has 30 to 150 or more yellow disc florets, 9 to 14 yellow ray florets (about half an inch long), and two rows of green phyllaries, all reaching approximately the same height. Those in the outer row are broader and lanceolate in shape, while those in the inner row are narrower, more numerous, and ovate in shape. Ray florets have two notches at the tip.