Broadly defined, this infamous species ("poison ivy") occurs across eastern North America and in se. China. Although widespread across Ky. and locally abundant, it is curiously infrequent at some west-central localities. It is eaten by livestock, which perhaps reduce it after long periods of intensive browsing. Rabbits may also eat it in winter (Terrel 1972). Variation needs more study, and segregates are not mapped here. Most plants in Ky. have glabrous fruit, and glabrous to moderately hairy leaves (glabrous above, strigose below); leaves are often notched to lobed. These characters match the largely midwestern var. negundo (Greene) Reveal. Var. radicans, with papillate to hairy fruit and largely glabrous entire leaves, is more common east of the Appalachians, especially on the Atlantic Coastal Plain (Cr, W). It was reported by Gillis (1971) from BELL to TRIG (Mich. State Univ.); see also W. Var. pubens (Engelm. ex S. Wats.) Reveal, with glabrous fruit but more hairy leaves (velutinous with erect hairs below, and somewhat hairy above), occurs mostly in the lower Mississippi Valley, especially on dry calcareous sites west of the river. It was reported by Gillis (1971) from FAYE in Ky. and from Rutherford Co. in Tenn. See also notes under T. pubescens.