This is a widespread eastern species of somewhat mesic woodlands and edges. Most plants mapped here appear to be typical cordifolium, but variation needs further study; 2n = 16, 32 (FNA 20) and perhaps other numbers (Cr). See also notes under lowrieanum. Occasional plants appear hybridized with undulatum (e.g. NELS & ROWA at KY), urophyllum (JESS at KY), laeve (B), or other species. Some colls. (ADAI & TAYL at Field) are referable to var. polycephalum (Porter) Nesom, which is not recognized in recent treatments. Typical cordifolium is distinguished from related species by its rays usually bluish to pale purplish (versus brigher blue to white); phyllaries have obtuse to acute, purplish tips (versus usually more acute to acuminate, green tips) with moderately elongated blazes (L/W ca. 2-3); lower leaves are deeply cordate (versus usually less cordate to truncate) and deeply toothed (versus shallowly toothed to entire), with scarcely or obscurely winged petioles (versus often strongly winged). Plants vary in pubescence, but are typically not glabrous or densely hairy. More western plants in Ky. may have paler colored rays in general, and further investigation is needed; a similar trend appears to exist in S. prenanthoides.