Stems erect, 20-80(-120) cm. Cauline leaf blades lanceolate to linear, reduced distally (becoming bractlike near heads), margins usually serrate apically, rarely entire. Peduncles stipitate-glandular, sometimes hispid as well. Involucres campanulate, (3.5-)5-8(-10) mm diam. Ray florets (10-)13-21(-29); corolla laminae 6-12 mm. Disc florets (20-)33-70(-108). 2n = 10, 12, 14.

Morphologic differences among the three varieties are slight and they form a closely coherent group within the genus; corresponding differences in geography, habitat, and chromosome number provide a rationale for maintaining the taxonomic and nomenclatural distinctions. B. L. Turner et al. (2003, vol. 1) treated var. hookerianum as including var. graniticum. B chromosomes sometimes are present and appear to increase the number by a pair (E. B. Smith 1966).