Toxicodendron rydbergii (Small) Greene

• Authority

  Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.

• Family

  Anacardiaceae

• Scientific Name

  Toxicodendron rydbergii (Small ex Rydb.) Greene

• Description

  Species Description - Vigorously rhizomatous and colonial, suberect, simple or sparingly branched shrub to 1(–3) m; lvs tending to be approximate toward the top of the stem; petioles elongate, glabrous; lfls broadly ovate to suborbicular, tending to be openly folded along the midrib rather than flat, glabrous on both sides, or strigose beneath and often with a line of minute, curly hairs along the midrib above; infl unbranched (racemose) or sparingly branched, usually with fewer than 25 fls; frs 4–7 mm thick, smooth, sessile or subsessile and crowded in a ± erect infl; otherwise much like no. 4 [Toxicodendron radicans (L.) Kuntze], with which it intergrades to some extent; 2n=30. Open, sunny habitats; widespread in w. U.S., extending e. in n. U.S. (especially north of the 42nd parallel) and s. Can. to N.S. and N.Y., thence s. at upper elev. to Va. and W.Va.

• Common Names

  western poison ivy