Root Out Invasive Weed: Dog-strangling Vine

Dog strangling vine smothering other plant material.

Pink star-shaped flowers on this dog-strangling vine will make thousands of seeds. Notice the spear-shaped brown seed pods.

Dog-strangling vine, a pernicious perennial invasive weed, from the milkweed family, is our own northern version of American kudzu , the “vine that ate the south”. Unlike our native milkweed, which is a host to the Monarch butterfly, Dog-strangling vine, or pale swallowwort (Vincetoxicum rossicum syn. Cyanchum spp.) has no redeeming qualities. It spreads by airborne seed and by roots, so it quickly chokes out native vegetation in meadows and forests. Parts of our Toronto Park system, and the Don Valley ravine are completely clogged with it. Helen Battersby, of Toronto Gardens blog has been on a mission to educate about dog strangling vine, and writes about this noxious weed’s impact on our environment:

If you like butterflies, you’ll be dismayed to learn that this milkweed relation confuses Monarch butterflies into laying eggs on it. Larva that hatch on these leaves don’t get the protection that milkweed provides. Bye bye, butterflies. And bye bye, native milkweeds, too, along with a host of other native wildflowers, choked out by the voracious growth of these bullies. Everywhere.

How to Identify Dog-Strangling Vine

The vines have a twisty growth pattern, winding around itself and/or other plants. A colony grows toward the light,  so in well colonized areas you’ll see many vines stretching out at the same angle, making a uniform pattern.

  • Single vines often pop up randomly in home gardens. Look for a sinewy upright growing stalk with arrow shaped opposite leaves. Cut them out where ever you see them.
  • Long, pointed seed pods are green, then turn brown, when mature
  • Seed pods are spear shaped, pointy at ends. Seed pods burst in August and float on the wind the way dandelion and milkweed seeds do

Get rid of Dog-Strangling vine the right way. 

  • Don’t pull vine upward, the way you do with other weeds: cut the vine stem at ground level with a knife. Pulling on stem breaks roots, causing more vines to start at the break.
  • If you have access, dig up entire root ball and destroy whole plant.
  • Don’t home compost the plant material or seeds
  • Dispose in garbage, not city compost. Or burn.
  • For heavily infested areas, remove all plant material, then smother area heavily with plastic for at least two years.
  • Be vigilant, destroy any new growth as soon as you see it.
  • Dog Strangling vine (DSV is its nickname) is on the Government of Ontario’s Invasive Species list, as part of their Invasive Species Strategic Plan for 2012. As for the scary-sounding name, here’s some reassurance that at least dogs aren’t actually harmed by this devious plant.

Its botanical name, Cynanchum, is from the Greek, kyon means dog and ancho to strangle, hence its common name, dog strangling vine, but there are no reports of it strangling a dog; plants, however, are another story.

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