This is a distinct and relatively uniform northeastern species. It is locally common in the Cumberland Mts. of Ky. but rare further west. Some of the outlying colls. from FRAN (KY-Agr.), OLDH (DHL), MASO (M), MEAD (PH) and TAYL (KY) might be from escaped or cultivated plants, but the species is considered native in s. Ind. (D; M. Homoya, pers. comm.). The genus Rubacer contains only one other definite species, the western R. parviflorus (Nutt.) Rydb. It differs from Rubus sensu stricto as follows (FNA 9, W and citations): leaves simple, palmately lobed (versus 3-9-foliolate); stems perennial with peeling bark, unarmed (versus generally biennial with distinct primocanes, not peeling, armed with prickles); 2n - 14 only (versus 14 to 63). Rubacer is close to the few species placed in Oreobatus Rydb., which occur from southwestern states to Guatemala; those species have smaller leaves and hairy styles (FNA 9). The combination of these two genera can be described as follows (Huang et al. 2023): "shrubs, erect or spreading, bark thin and peeling, unarmed, leaves simple, maple-like, digitately ribbed and lobed, styles club-shaped, glabrous or hairy, stigmas slightly 2-lobed, receptacles flat, drupelets capped by hard hairy cushions or without cushions; diploid".