- Dog-Strangling Vine, Cynanchum rossicum, (also known as Pale Swallow-wort), is an invasive, perennial vine that can grow over 6 feet in one season. Once established in a garden, it is very difficult to eradicate. Early detection with removal, is the best opportunity to slow its ability to colonize gardens or natural areas.
2. The stems begin upright, with no support, and then begins to twine and climb dependent on available supports (i.e., fence, trees); or will twine with other DSV to create a mat covering the ground.
3. It resembles milkweed, having opposite leaves, with a similar leaf shape, milky sap and seed pod. Monarch Butterflies unfortunately mistake it for milkweed and lay eggs which do not survive when they hatch.
4. It has a small purplish-brown flower in May/June/July. It has been observed along roadsides, fences and trails in Southern Ontario.
5. It is harmless to dogs (although if ingested there is literature reporting that it can be harmful to mammals) however off-leash dogs can unwittingly spread seed on their coat. (…so can humans, on shoes, boots, bicycle tires etc.). In natural areas, leash your pet, CLEAN paws, fur, clothing, boots, shoes etc!
6. It reproduces by seeds and underground rhizomes (stems that are under the soil). One square meter can produce 20,000 seeds which are viable for several years. It colonizes on hillside, ravines, fences & disturbed soil in dappled shade & full-sun.
7. Dog Strangling Vine is a problem because:
- It shades out native plants that provide habitat and foraging areas for both birds and insects of our region
- It is toxic to leaf-eating insects from our region
- In forests, tree seedlings are unable to grow because they can’t compete for light and other resources.
8. Controls include:
- Cut the stem, just below the soil level, re-checking throughout the season, to prevent the plant from growing and producing flowers or seed. This will also eventually starve the roots.
- If you don’t have time for removal – cut off any flowers or seeds pods and dispose (see note re disposal) to reduce the ability to spread
- DO NOT try to pull larger plants. The roots will splinter and produce more plants!Remove rootstock and all plant parts from the ground so it doesn’t re-sprout
- Bag in contractor bags and place in the sun to solarize or put discarded plants in regular garbage (Do NOT compost or put in yard waste). Some people choose to compost stems and leaves, but roots and seed pods must be put in regular garbage.
- Mow plants consistently – preventing them from going to seed throughout the season
- NOTE: care should be taken in removal as it may cause skin reactions in some individuals (i.e, waterproof gloves).
9. Best Practices
- Plant areas with native species or cover crops to fill the area to prevent seeds from germinating
- Tilling the soil can increase infestation of DSV – as it cuts the roots into multiple pieces with potential to re-grow
- Mulching an area (thick layer of leaves or newspaper), immediately after removal may help in the recovery of native plants
10. If you see a new infestation of dog-strangling vine or other invasive species in the wild, contact the toll-free Invading Species Hotline:
- 1-800-563-7711 or visit EDDMapS Ontario to report a sighting. http://www.invadingspecies.com/dog-strangling-vine/