This diploid (2n = 8) occurs on dry sandy soils in southeastern states east of the Mississippi Rv. In Ky. almost all records are from roadsides on or near sandstone outcrops in the southern Cliff Section of the Appalachian Plateaus. There are no records from nearby clifftops. The concolor group appears closely related to the pratense group, but there is striking divergence in relation to soil (acid versus basic). The concolor group has less branched stems, smaller leaves, smaller heads, and strigose seeds (versus glabrous); also n = 8 versus 10 (FNA 20).