Cynanchum louiseae (Kartesz & Gandhi)
Synonym: Louis' swallow-wort
Black swallow-wort is native to Europe, and may have been introduced intentionally for ornamental purposes or imported unintentionally on other plants or materials. It threatens native flora in fields, forest edges, woods and open disturbed areas. It grows vigorously and densely, blocking light from reaching the plants it scrambles across, often leading to their death. Black swallow-wort spreads vegetatively and by seeds dispersed by the wind. Black swallow-wort is particularly troublesome in open areas and along edges and banks where it grows over other vegetation, blocking light and creating tangled thickets. It alters and degrades natural habitat by crowding out native plants and is a threat to rare species. Because there are many native milkweed species in the United States, correct identification of this plant is imperative.
Black swallow-wort it is known from only two places in Indiana: a backyard in Marion County and at Hayes Arboretum near Richmond (Wayne County).