A genus of 5-8 species, shrubs and trees, of e. and sw. North America. The Southern Appalachians are a center of diversity of Robinia, with active hybridization, introgression, and formation of local (sterile) races involved; a fully satisfying taxonomic treatment of such a situation is not possible. Isely & Peabody’s (1984) and Peabody's (1984) treatment seems a reasonable approach, and I have largely followed it here, differing in the rank of some of the taxa.
ID notes:The key is differently structured than that in RAB or SE; it is presented as an alternative. This treatment may be altered substantially prior to publication. A variety of hybrids (including some cultivars) are known, including the following: Robinia ×longiloba Ashe (pro sp.) [R. hispida × viscosa], known from NC and SC; Robinia ×margaretiae Ashe (pro sp.) [R. hispida × pseudoacacia], known from NC, SC, and GA; Robinia ×ambigua Poiret (pro sp.) [R. pseudoacacia × viscosa], known from NC; Robinia hartwigii × hispida, known from Whiteside Mountain, Jackson County, NC; Robinia hartwigii × viscosa, known from Whiteside Mountain, Jackson County, NC.