This small tree is widespread on well-drained fertile lowlands across southeastern states, but largely absent from the Appalachians and Interior Low Plateaus (K). Most or all Ky. colls. are referable to var. discolor (Pursh) Gray, which is a relatively western segregate (F) with leaves broadly elliptic to oblong-obovate, up to 4-8 cm wide (versus lance-elliptic to lance-ovate, up to 2-6 cm wide), and "velvety to tomentulose" below (versus glabrous to glabrate). However, Hardin (1957a) and others have not recognized this variety. Outlying colls. from HENR (KY) and ROWA (KY) may be atypical, and perhaps hybridized with other species. Alternatively, they may have come from cultivated or escaped plants. Unverified reports from FAYE (CW), FLOY (Gm), FRAN (K), MONR (Gm). OWEN (K) and SCOT (Gm) are not mapped here. Hardin (1957b) reported hybrids of pavia with A. sylvatica Bartr. from BELL (H.A. Gleason #8831 at NY) and from "southern Ky." (S.F. Price #2385 at GH). A. sylvatica is a more southeastern species, concentrated on the Piedmont and extending north in the Ridge-and-Valley region no further than Granger Co. in e. Tenn. (Ch). Moreover, DePamphilis & Wyatt (1989) and Modliszewski et al. (2006) indicated that flava and sylvatica in Tenn. and Ga. are partly introgressed with pavia; they discuss the potential for long-distance dispersal of pollen by humming-birds, spreading genes of southern populations into northern populations. The scarlet flowers of typical pavia appear especially suited to pollination by humming-birds, which also visit other species of Aesculus.