Without flowers or fruits, this largely midwestern species is often hard to distinguish from flava. Its bark lacks the frequent platy character of flava; its leaflets tend to be smaller (mostly 8-16 cm long versus 12-24 cm) and more fetid. The "stinking" nature of this species may be associated with its toxic saponin composition, which has been analyzed by Yuan et al. (2011). Hardin (1957b) considered that some colls. of glabra scattered west of the Appalachians in Ky. (BULL, FAYE, CLAR, MADI at GH), Tenn, Ohio, Ind., Ill., Mo. and Io. exhibit introgression from flava; see also Beatley (1979). But in many cases this conclusion just came from the presence of stipitate glands on pedicels and perianths. Evidence of introgression is clearest close to the Appalachians, often with stamens less exserted, greater differences between upper and lateral petals, and fruit spines relatively small or irregular. Past or present occurrence of glabra within the rugged Appalachian hills of Ky. remains uncertain. CW mapped it in CLAY based on a vegetative coll. (EKY) with identify uncertain. Gm listed several other Appalachian counties that are not mapped here. Yet glabra is known nearby from sites in s. W.Va., and more frequently in the Ridge and Valley of Tenn. and Va. (K). A. glabra is largely restricted to base-rich soils in Ky., where it can become locally dominant, at least in the subcanopy. Its early leafing in spring is associated with generally reduced ground vegetation during summer, especially Podophyllum, but perhaps the opposite for Laportea (Hicks & Taylor 2015). Cattle and deer can promote the glabra by browsing selectively on more palatable trees. In the central Bluegrass, Short (1828-9) noted: "This species is abundant throughout the forests in the rich lands of Kentucky ...it is sometimes eaten by cattle, and often with fatal effects." The national champion of glabra is in Lexington (FAYE at 38.06214, -84.51934): 141 cm dbh, 26 m tall and 17 m wide in 2011 (KDF 2020).