Dog strangling vines, scientifically known as Cynanchum rossicum and Cynanchum louisae, were introduced to Canada by European settlers approximately 120 years ago. Like a wild fire, dog strangling vine spread across central and southern parts of Ontario and southern Quebec.
Figure 1. Picture of Dog Strangling Vine taken at Glendon Campus, York University.
What do they look like?
As observed in Figure 1, dog strangling vines grow 1-2 metres high and twine around plants, trees and structures, hence the name ‘strangling’. The leaves are green, oval shaped with a pointy tip. The leaves are 7-12 centimeters long and grow as pairs on opposite sides of the stem. Dog strangling vines grow dark purple/pink flowers which have five petals as shown in Figure 2. Lastly, the vines have long seed pods, about 4-7 centimetres long, which split in the late summer to release feathery white seeds as seen in Figure 3.
Figure 2. Photograph by Court Noxon. Dog Strangling vine flower.
Figure 3. Dog Strangling Vines feathery white seeds. Photo by Greg Bales, Ministry of Natural Resources.
What impacts do they have?
- Forms dense interwoven mats that crowd out native plants and saplings which leads to prevention of forest regeneration and loss of native species.
- They interfere with forest management and recreational activities.
- Browsing animals such as deer do not feed on dog strangling vine which increases grazing pressures on native plants that have already decreased in population size.
- Dog strangling vines closely resemble milkweed, which monarch butterflies lay their eggs on. However, on the vine the larvae are unable to complete their life cycle, and as a result the monarch butterfly is a species at risk in Ontario.
- Mechanical Control: physical removal methods of the vine species. Some examples of this are clipping, digging, and pulling.
- Chemical Control: use of prohibited herbicides and pesticides to control invasive species.
- Biological Control: use of another species such as herbivores, disease, or other natural enemy to reduce the population of invasive species.
- Report it: if you come across dog strangling vines, take a picture, record the location, and contact the invading species hotline 1-800-563-7711
- Stay on trails: don’t travel off trails in areas with dog strangling vines to avoid spreading seeds.
- Stop the spread: Ensure your clothes, shoes, pets, equipment, vehicles or anything that has been exposed to the invasive species are seed free
- Use native species in your garden and encourage your neighbors, friends and family to prevent use of invasive plant species.
Dog strangling vines are an invasive species in Canada that are spreading rapidly throughout Ontario and Quebec. We need to prevent further spreading of this species to protect our native species and thus native/natural biodiversity. On the bright side, however, dog strangling vines do not strangle dogs!