Mapping is provisional, pending further revision. Widrelechner (1998; see also K) interpreted this species as widespread across northeastern states and especially in the upper midwest. Ladd & Thomas (2015) stated that it appears to be the second most abundant Rubus in Mo. after argutus, but with the same habitat; but they appear to have inc,uded most "pensilvanicus" records. R. frondosus is reported to have relatively numerous large foliaceous bracts, but their distinction and correct name remains uncertain; see notes under pensilvanicus, which may be difficult to distinguish. Compared to argutus, both taxa have broader ovate terminal leaflets on primocanes, widest at or just below the middle (versus above), also their leaves tend to be thinner and more softly pubescent (Ladd & Thomas 2015).