This northeastern species typically occurs on "calcareous rocks, ledges and cliffs along rivers" (FNA 20). In Ky. it is known from EDMO (DHL but perhaps mislaid): A.T. Hotchkiss 69-9-27-3, 27 Sep 1969, "in rocky crevices, moist sandstone cliffs above east end of Nolin River dam" [where there is much intermixing of base-rich and non-calcareous soil parent material]. It has also been reported from se. Ky., where there may be intergradation with arenicola. Plants along the Rockcastle (LAUR and PULA) main Cumberland (WHIT and some MCRE), Obed and Emory Rivers, have glabrous achenes as in typical arenicola, but relatively small heads. Plants along the Big South Fork in Ky. and Tenn. (including part of the MCRE material) have distinctly hairy achenes and smaller heads, with involucres only 5.5-7.5 mm long and more numerous per head (13-19), in more congested inflorescences. These characters suggest intermediacy between arenicola and racemosa. The whole North American complex based on simplex (sensu lato) includes a polyploid series (2n = 18, 36, 54), but only tetraploids (2n = 36) are known in arenicola and racemosa (FNA 20, Peirson et al. 2012).