As generally circumscribed (FNA 20), dumosum is a highly variable species or species-complex (with 2n = 16 or 32), and further analysis is needed. (In the Ozarkian region it is largely replaced by S. turbinellum (Lindl.) Nesom, with 2n = 96.) In Ky. dumosum is generally associated with acid soils and virtually absent from the Bluegrass region. The lone coll. from FAYE (EKY ex KY-Agr.) was labelled "Lexington... yard" (by H. Garman, 21Sep1933); however, it has been recently discovered in an old field of GARR (EKY) above the Ky. Rv. Palisades It is usually recognizable from its pale bluish flowers on relatively long peduculate branches with highly reduced linear to subulate leaves; leaves are usually glabrous; stems are usually colonial from spreading rhizomes. Var. dumosum sensu stricto is centered in northern Appalachian regions and unknown in Ky. (F; J.C. Semple, pers. comm.). The widespread southeastern segregate, A. dumosus var. coridifolius (Michx.) Torr. & Gray, has been combined with typical dumosum in most recent treatments. However, it does appear distinct and includes most dumosum in Ky. Var. coridifolium occurs mostly on open grassy uplands with seasonally dry, acid soils. Although occasional hybridization and intergradation with other species has been suspected, there is no clear evidence of such processes in Ky.