This occurs on well-drained base-rich soils in east-central states from the Mississippi Rv. to the Appalachians, and it appears to be adventive in northeastern states (K). Although generally considered a distinct species, calycosus varies much in flower color, flower size, leaf width, and pubescence. Typical plants on lowlands in w. Ky. (CHRI, LYON, etc.) and most plants in Tenn. (D. Estes, pers. comm.) have flowers flushed with lavendar to purple, generally glabrous stems except for lines of hairs, and generally glabrous leaves (Pennell 1935). Colls. mapped here from CALL and MCRA (MUR) have relatively narrow leaves, suggesting transitions to laevigatus; see notes under that name. Most calycosus in the central Ohio Valley, at the center of its modern range, has whitish flowers and stems with distinctively dense short hairs (ca. 0.1-0.5 mm); some of these plants may be transitional to digitalis or alluviorum.