It is called dog strangling vine — and, although it does not actually harm any animals, cynanchum rossicum is one of the most harmful invasive species posing a threat to local biodiversity.
Janet Mills, co-president of the Bond Head/Bradford Garden Club, discovered a large patch of the plant next to the club’s pollinator patch at the Danube Seniors Leisure Centre.
At first, she said she did not recognize the species — but once she did the research, she was appalled.
Also called black swallow-wort, it is native to Eurasia and was introduced to North America by gardeners as an exotic plant and quickly escaped into the wild, according to Ontario’s Invading Species Awareness Program.
In its early stages, it stands one to two metres high and resembles milkweed, with its opposite leaves.
It is only later, as it matures, that it becomes vine-like, its stems intertwining, clinging to trees and shrubs, and creating a dense cover that will choke out most other plants.
It reproduces from seed, producing about 28,000 seeds per square metre, but also from plant fragments and roots — making it difficult to eradicate.
It is a particular problem in Ontario’s forests, where it can form stands that prevent the regeneration of the understory.
The only way to eradicate dog strangling vine is with repeated mowings. Pulling up the plants can leave root fragments that will regenerate quickly.
Clipping off the flowers and seed pods can also prevent its spread, but any cut plant material cannot be composted.
Instead, it should be bagged in a black plastic garbage bag, and left to “cook” in the full summer heat.
For more information on dog strangling vine and its eradication, visit invadingspecies.com.