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Ministry of Agriculture, Food and Rural Affairs


Scientific Name: Vincetoxicum nigrum (L.) Moench

Other Names: cynanque noir, Black swallow-wort, Cynanchum nigrum (L.) Pers.

Family: Milkweed Family (Asclepiadaceae)

General Description: Perennial, reproducing by seed and by spreading underground rhizomes. All parts of the plants may contain small quantities of white, milky juice.

Habitat: Dog-strangling vine occurs in several localities in southern Ontario, growing in ravines, hillsides, waste areas, fence lines and hedges.


  • Vine-like
  • Herbaceous or with woody base which overwinters successfully in Ontario
  • 1-2 m (3-6 ½ ft.) long
  • Scrambling or climbing over fences and other vegetation


  • Opposite (2 per node)
  • Oval to oblong with rounded bases and abruptly pointed tips


  • Purple-brown to dark purple
  • Small, in small umbel-like clusters at tips of stems and upper branches
  • Seedpods:
    • Slender
    • 4-6 cm (1 ½- 2 ¼ in.) long
    • Broadest near the base and long-tapered to a slender tip
    • Opening along one side and releasing many seeds
  • Seeds:
    • Small
    • Flat
    • Brownish
    • With long, white, silky parachutes
  • Flowers from late June until autumn

Often Confused With
Milkweed (for the pods)
Wild grape (for the twining vine)
It is distinguished by its perennial vine habit, opposite leaves, purplish flowers, slender seedpods with parachute seeds, and somewhat milky juice.

Dog-strangling vine

Dog-strangling vine. A. Base of plant with flowering branch. B. Twinning of branches with 2 open seedpods.Click to enlarge.