This occurs mostly on subhydric soils in the central Mississippi and lower Ohio Valleys. It is close to digitalis (Pennell 1935, W) but with smaller capsules (5-9 mm versus 9-12 mm), shorter corollas (mostly 15-23 mm versus 20-32 mm, and more often purplish), shorter sepals at anthesis (mostly 2-5 mm versus 5-8 mm, and less scarious-margined), inflorescences less glandular, leaves averaging narrower (mostly 2.5-4 cm wide versus 3-6 cm) and more pubescent, stems less lustrous and often more pubescent, at least in narrow lines. Ranges overlap, and mixed or intergrading populations have been found in Ky. (including some from plantings). Some authors have included alluviorum in digitalis (Cr, Y, FNA 17), but there may also be intergradation with laevigatus (D. Estes, pers. comm.). Indeed, alluviorum and laevigatus may not be clearly separable where their ranges overlap.