Mapping here is provisional. S. lowrieanum is often considered to be a largely Appalachian taxon close to cordifolium (Cr, W), and it has been combined in some treatments (FNA 20). In more distinctive plants, leaves are glabrous and slightly glaucous, with less serrated margins, less cordate bases (at least in upper leaves), and more winged petioles (F, J); phyllaries usually lack purplish tips. Those plants appear closely related to urophyllum, differing in their more obtuse phyllaries, with shorter green blaze (l/w ca. 1-1.5); and perhaps more open inflorescences (Cr, W). However, colls. mapped here mostly appear closer to typical cordifolium, and are assigned here based only on their virtually glabrous (and often slightly glaucous) leaves. These plants are largely restricted to Appalachian regions, but also extend west into more hilly sections of the Knobs and Bluegrass. Occasional colls. appear hybridized with other species, especially undulatum (e.g. from HARL at EKY, PERR at KY). Cronquist (1980, Cr) and others have suggested that lowrieanum is derived from hybrids between cordifolium and laeve (X schistosum (Steele) Nesom), but plants mapped here rarely occurs in the same habitat as laeve.