Vincetoxicum nigrum (L.) Moench
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.
Species Description - Climbing, 1–2 m; lvs short-petiolate, oblong to ovate, 5–10 cm, acuminate, rounded to subcordate at base; fls mostly 6–10 in umbelliform cymes on peduncles 0.5–1.5 cm; cor purple-black, its lobes rather fleshy, ± deltoid 1.5–3 mm, with tiny hairs 0.1–0.2 mm on the upper surface; corona inconspicuously 5-lobed; fr slender, 4–7 cm; 2n=44. Native of s. Europe, occasionally escaped from cult. in our range, and locally established in woods and moist, sunny places. June–Sept. (Cynanchum n.)