This largely midwestern diploid (2n = 34) is generally assigned adventive or uncertain status in most southeastern states (F, Cr, FNA 21, W). The species is probably native to Ky. in some remnants of grassland on deeper calcareous soils; it is locally abundant in remnants on the dolomitic foothills of LINC, GARR and MADI. However, it also appears to have spread locally along roadsides and into old fields of the Eden Shale Hills. There has been some confusion with giganteus and maxmilianii, and hydridization has been reported. H. grosseserratus (on more base-rich soils) and the closely related giganteus (on medium acid soils) are among the tallest perennial herbs in Ky., reaching 4-5 m under optimal conditions; see also Sida hermaphrodita. Compared to giganteus and maxmiliani, grosseserratus has leaves with longer petioles (ca. 1-5 cm versus 0-1.5 cm); also, the blades are larger (mostly 10-30 x 3-5 cm versus 8-20 x 1-3.5 cm), usually deep-serrate (versus shallow- to subentire), paler and densely puberulent below (versus green and scabrid-hirsute). Its rhizomes tend to be more elongated, sending up colonial stems that tend to be less hairy in the inflorescence and more glaucous, but these are not diagnostic differences. Heads of grosseserratus tend to be larger, with rays 2-4.5 cm (versus 1.5-3 cm), and with less marginal pubescence on phyllaries and disc florets.