This is widespread in eastern states except the upper mid-west, ranging from dry sites to (especially further south) damp sites, In Ky. it is the most common "greenbrier" of Smilax section China (all with 2n = 32), and especially common in understories of subxeric woods, but rare to absent on richer soils. Descriptions differ and variation deserves further study (e.g. D, F, SC, Y, FNA 26). Its peduncles are generally short, more or less equalling petioles, unlike other greenbriers in the state, but this character alone can be unreliable. Umbels tend to have relatively few flowers (usually 4-10 versus 8-25 in other species). An acutely obvious character is that stout greenish prickles are scattered along most internodes except smaller branches (versus concentrated towards plant base). Also, in dry upland habitats of Ky. most internodes are clearly 4-angled (versus terete or slightly angled); however, the status of var. quadrangularis (Muhl. ex Willd.) Wood remains uncertain. The leaves of rotundifolia dry to pale brownish-green with a raised network of veins; minute irregular projections are usually scattered along thin margins and on veins below, at least towards the base. Leaves are strictly deciduous in Ky. (not even semi-evergreen as indicated further south), unlike the other species, but stems remain green and much browsed by deer (Campbell 2013). Plants have spreading rhizomes, while distal internodes often develop a highly branched, shrubby growth form. Two species of southeastern lowlands resemble rotundifolia in their relatively short peduncles: S. walteri Pursh (with red versus black berries, plants drying more reddish, leaves narrower, revolute and smooth, stems less angled, prickles subulate and concentrated at bases) and S. laurifolia L. (with unilocular ovaries, purplish berries, narrower more coriaceous evergreen leaves, and fewer distal prickles). Reports of those two species from Ky. have likely been erroneous (M), but walteri has been verified from nc. and w. Tenn. (Wilbur 1967; Ch).