This diploid is widespread on wet lowlands across most of eastern North America, but concentrated on somewhat acid (or oligotrophic) soils. It is uncommon to absent west of the Mississippi Rv. and on the Gulf Coastal Plain (K). In Ky. it is largely absent from the Bluegrass region. R. palustris differs from carolina in its stouter, often hooked, infrastipular stipules (suggesting virginiana), its stipules with a longer adnate ("caniculate") portion, and its leaves with more numerous, finer serration (F). Stems of palustris are sometimes unusually red when fresh. BA's report of the more northern species, R. blanda Ait., was based on a misidentified coll. of palustris from EDMO (KY).