(Kleopow) Borhidi [= Vincetoxicum rossicum (Kleopow) Barbar.] and Cynanchum louiseae (L.) Kartesz & Gandhi [= Vincetoxicum nigrum (L.) Moench]. Can. J. Plant Sci. 85: 243-263. Cynanchum rossicum (dog-strangling vine) and C. louiseae (black dog-strangling vine) are introduced, perennial herbs or small twining vines in the Milkweed family (Asclepiadaceae). Generic placement of these two species has been problematic, but are here treated as members of Cynanchum subgenus Vincetoxicum. The species occur primarily in natural upland areas, including understories of woodlands, pastures, old fields, shores, flood plains and ruderal areas of southern Ontario and Quebec and the northeastern United States. Ecosystems on well-drained, stony soils are often densely colonized, but both species can tolerate a wide moisture regime. Plants establish in full sun or under forest canopies and may form monospecific stands in all light conditions. They often form dense colonies which smother other vegetation and reduce invertebrate and vertebrate biodiversity. Reproduction is by polyembryonic, wind-dispersed seeds. Effective control is primarily by herbicides, since mechanical control is difficult and no biological control agents have been developed. A third European species, C. vincetoxicum, has been reported as an occasional garden escape in southern Ontario and the northeastern United States, but has not yet become naturalized. Information on this species is included because of its close relationship with C. rossicum and its better known biology. DiTommaso, A., Lawlor, F. M. et Darbyshire, S. J. 2005. Biologie des plantes exotiques envahissantes au Canada. 2. Cynanchum rossicum (Kleopow) Borhidi [= Vincetoxicum rossicum (Kleopow) Barbar.] et Cynanchum louiseae (L.) Kartesz & Gandhi [=Vincetoxicum nigrum (L.) Moench]. Can. J. Plant Sci. 85: 243-263. Cynanchum rossicum (cynanche) et C. louiseae (cynanche noir) sont des herbacĂ©es vivaces ou de petites vignes exotiques de la famille de l'asclĂ©piade (AsclĂ©pidadacĂ©es). La dĂ©ter-mination du genre des deux espĂšces s'est avĂ©rĂ©e difficile, mais on a convenu de les classer dans le sous-genre Vincetoxicum de Cynanchum. L'espĂšce affectionne surtout les plateaux naturels, y compris les sous-Ă©tages des boisĂ©s, des pĂąturages, des champs en friche, des rivages, des plaines inondables et des zones rudĂ©rales du sud de l'Ontario et du QuĂ©bec ainsi que du nord-est des Ătats-Unis. L'Ă©cosystĂšme des sols rocailleux bien drainĂ©s est souvent densĂ©ment peuplĂ©, mais les deux espĂšces tolĂšrent de fortes variations d'humiditĂ©. Elles s'Ă©tablissent au soleil ou sous la canopĂ©e forestiĂšre, oĂč elles constituent parfois des peuplements monospĂ©cifiques, peu importe la luminositĂ©. Leurs denses colonies Ă©touffent souvent les autres plantes et rĂ©duisent la biodiversitĂ© des invertĂ©brĂ©s et des vertĂ©brĂ©s. Les deux espĂšces se multiplient au moyen de semences Ă embryons multiples dispersĂ©es par le vent. On en vient surtout Ă bout avec des herbicides, car aucun agent de lutte biologique n'a Ă©tĂ© mis au point et le dĂ©sherbage pa...