This is widespread across temperate North America but concentrated in southwestern regions and the Great Plains. It is disjunct in scattered regions of more eastern states, where it occurs locally in xeric calcareous clifftops, glades and glasslands (FNA 25). [An old record from FAYE is not accepted here, due to confusion with colls. of C.W. Short from "mountains of Kentucky".] Variation deserves further research; reportedly, 2n = 20 to 103 (FNA 25).