This frequently planted diploid (2n = 20) is not native to Ky., and probably originates from the southern Blue Ridge in N.C. and Tenn. (Isely & Peabody 1984; W). It has been confused with the triploids (2n = 30), hispida and boyntonii, which are native to Ky.; see also note on hybrids under kelseyi. The "Arnot bristly locust" cultivar of fertilis was developed in the 1960s and became widely grown after 1971 for reclamation of coal mines as well as ornamental use, In Ky. fertilis often persists and escapes; the degree of naturalization is often unclear from collection data.