This largely northeastern and Appalachian species is generally distinct from the more southern rotundifolium (F, FNA 21, W), but it has often been treated as a variety (Cr). E. pubescens appears to be an apomictic allopolyploid (mostly with 2n = 30), derived from rotundifolium and perhaps sessilifolium; occasional plants with more elongated leaves may be transitional to (or confused with) X godreyanum (pinnate-veined versus trinerved from near the base) or even to sessilifolium var. brittonianum (L/W ca. 3 and glabrous below infloresence). There may also be some intergradation between pubescens and rotundifolium across their ranges (F, Cr), as suggested by some colls. from Ky. (e.g. B). Chemistry of the rotundifolium complex has received little investigation, but its sesquiterpene-lactone can inhibit tumors (Herz 2001, and citations); smell and taste can induce nausea in people working with large volumes of material (J. Seymour, pers. comm.).