This is a relatively uniform diploid (2n = 34), widespread in thin woods and edges across eastern and southeastern states (K, FNA 21; Stephens et al. 2015). However, there is some variation in leaf pubescence and glaucousness, which may warrant further investigation (W). Also, there may be rare hybrids with divaricatus (especially), hirsutus and other species. In addition to its distinctively small heads (with involucres only 5-7 mm high), microcephalus has leaves with usually tomentulose lower surfaces (versus less densely hairy in divaricatus and hirsutus), petioles mostly 0.5-2.5 cm long (versus sessile in divaricatus) and stems glabrous (versus hirsute in hirsutus).