Black dog-strangling vine, black swallowwort
Vincetoxicum nigrum (L.) Moench


Cynanchum louiseae is an herbaceous, twining, unbranched, perennial vine which can grow up to 6.5 ft. (2 m) in length.
Leaves are opposite, dark green, oval, and shiny with entire margins. Leaves are from 3-4 in. (7.6-10.2 cm) long and 2-3 in. (5.1-7.6 cm) wide. A short petiole attaches the leaf to the vine.
Clusters of 6-10 flowers bloom from June to September. Five lobed dark purple corollas are approximately 0.25 in. (0.6 cm) across and covered with short white hairs on the upper surface.
Fruit are pods, similar to milkweed pods, which are slender, 2-3 in. (5.1-7.6 cm) long and split to reveal small seeds with tufts of white hairs. The hairs allow the seeds to be readily dispersed by wind. Plants have rhizomes that sprout new plants.
Ecological Threat
Cynanchum louiseae readily invades upland areas. It tolerates a wide range of light and moisture conditions and can be found invading a wide variety of upland habitat types. It is native to Europe. The history of its introduction is uncertain, but it may have escaped from a botanical garden.


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EDDMapS Distribution

EDDMapS Distribution - This map is incomplete and is based only on current site and county level reports made by experts, herbaria, and literature. For more information, visit

State Regulated List

State Regulated List - This map identifies those states that list this species on their regulated list. For more information, visit

Taxonomic Rank

Kingdom: Plantae
Phylum: Magnoliophyta
Class: Magnoliopsida
Subclass: Asteridae
Order: Gentianales
Family: Asclepiadaceae
Genus: Vincetoxicum
Subject: Vincetoxicum nigrum (L.) Moench

Synonyms and Other Names

Other Common Names:
Louis' swallow-wort

Related Scientific Names:
Cynanchum louiseae Kartesz & Gandhi (Synonym)
Cynanchum nigrum Kartesz & Gandhi (Synonym)


Plants - Vines