Robyns' aster is an erect forb, 20cm-1.4m tall, with an inflorescence with few to several heads in an open cluster, with 20-50 pale purple petals, each 6-14mm long. Fruits are brown, inversely ovoid, cypselae 2-4mm, with faces that have infrequent or no stiff, sharply appressed hairs. Leaves are thick and firm, lance-shaped or elliptical, 4-17cm x 4-25mm, sessile, toothed or entire, and smooth except for the rough and hairy perimeter.