Cynanchum louiseae (Vincetoxicum nigrum; Cynanchum n.) Louise’s swallow-wort; black swallow-wort Asclepiadaceae VINI*p; Bx, pb; NY, ct; Q a; K, m; R;

Vincetoxicum nigrum.commons.wikimedia.org

Vincetoxicum nigrum.commons.wikimedia.org (Accessed 7/2014).

Cynanchum louiseae is a perennial, herbaceous, twining vine 1-2 m long, from a large root crown and colonial from rhizomes, usually unbranched. 

Leaves opposite, stalk short; blade 5-10 cm long, oblong to egg-shaped, tip long-pointed, base rounded to slightly lobed. 

cynanchum-louiseae-black-swallow-wort-flowers-title-pic-sleloinvasives-org

Cynanchum louiseae.black swallow wort flowers-title-pic.sleloinvasives.org

Flowers blackish-purple, radially symmetrical, petal lobes 5, triangular, fleshy, 0.2-0.3 cm long; inflorescence, umbrella-shaped, rather few-flowered; blooming June-Sept. 

Fruit dry, hollow pods in pairs, 4-7 cm long, narrowly elliptic; seeds brown, flat to 0.7 cm with winged margin and silky plume (Uva et al. 1997).  

Wetland status: UPL. 

Frequency in NYC: Infrequent. 

cynanchum-louiseae-fruit-leslie-j-mehrhoff-university-of-connecticut-bugwood-org-sleloinvasives-org

Cynanchum louiseae fruit.Leslie J Mehrhoff.University of Connecticut.bugwood.org.sleloinvasives.org

Origin: Southern Europe. 

Habitat: Moist, open or partly shaded habitats. 

Notes: Very aggressive, smothering native vegetation, can kill small trees. Listed as one of the NYS ”top twenty” invasive plants by the DEC Natural Heritage Program.