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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