This is a largely midwestern species, mostly from Minn. and Wis. to e. Texas (K, W). There are scattered disjunct records east as far as the Ridge-and-Valley from Ala. to Md., but the identification of some eastern records may be doubted. S. drummondii is generally distinct, but it may occasionally hybridize or introgress with urophyllum, cordifolium, shortii and undulatum (Cr; FNA 20, Y). Introgression with cordifolium may have increased after settlement in Mo. (St). Compared to urophyllum (perhaps the most similar relative), drummondii is densely hairy (versus thinly); phyllaries usually have less elongated green blazes (L/W ca. 2-3 versus 4-5); and rays are usually bright blue (versus pale bluish, lilac or white); FNA 20 reported 2n = 16 and 32 versus just 16. However, drummondii is also uncomfortably close to cordifolium, with distinction based largely on the following characters (FNA 20): lower stems glabrous to sparsely hirsute (versus glabrous); upper stems densely hirtellous to hirsute (versus sparsely hirtellous or pilose); basal leaf blades averaging smaller, mostly 1-8.5 x 1-6 cm (versus 3.5-15 x 2.5-7.5 cm); lower leaf surface scabrous to densely piloso-strigose (versus glabrous or sparsely to densely strigose-pilose); phyllaries with green zones lanceolate to linear-lanceolate (versus lanceolate to ± diamond-shaped). Thus, relatively hairy forms of cordifolium may be impossible to separate from drummondii.