Broadly defined, this complex species is widespread on xeric base-rich sites across North America, with several regional or local segregates that can be recognized (SC, W; R. Dever & D. Ford-Werntz, pers. comm.). Some plants in w. Ky. (in rocky glades of LOGA) appear more robust and flower later, suggesting a transition to stellatum, but without the spreading stellate corolla of that species. See also notes under stellatum, which may have been confused in some cases; 2n = 14 in both species. With some biogeographic parallels, cryptic variants may also exist among associated xerophytic calciphiles in Sedum, Mononeuria, Cerastium, Houstonia, Rudbeckia and Sporobolus.