Dog-Strangling Vine
Cynanchum rossicum / Cynanchum louiseae
A twining perennial vine in the milkweed family that smothers other plants. It forms dense mats, climbs over vegetation, and releases fluffy wind-blown seeds from slender pods.
Dog-strangling vine — a twining vine that forms dense colonies.
Image source: Ontario weed-identification reference (OMAFRA / Ontario CropIPM)
At a glance
- Key clue
- Twining vine with dark star flowers and fluffy-seed pods
- Best months
- July to September, when flowering and seed pods are present
- Often found
- Backyard, Ravine edge, Vacant lot, Fence line
- Easiest to remove
- Spring (dig roots)
Why it's prohibited
Dog-strangling vine grows over and smothers native plants, shrubs, and young trees, forming dense monocultures and releasing chemicals into the soil that inhibit other species (allelopathy). It also harms monarch butterflies, which mistakenly lay eggs on it because it is related to milkweed.
Main identification features
- Twining vine that wraps around plants and stems, 1–2 m long
- Oval, pointed leaves arranged in opposite pairs along the stem
- Small star-shaped flowers, pink-brown to dark maroon, in summer
- Slender bean-like seed pods, 4–7 cm, that split to release fluffy seeds
- Grows in dense, tangled patches that choke out other plants
Similar plants & look-alikes
- Native milkweed — Milkweed stands upright and does not twine; it has larger pink flower clusters and thicker pods.
- Bindweed — Bindweed has white-to-pink trumpet flowers and arrowhead leaves, unlike the small dark star flowers of DSV.
Month-by-month identification timeline
July to September, when flowering and seed pods are present.
April–May (Early spring)
· 10–40 cmNew shoots emerge and begin to twine; paired oval leaves unfold.
Twining shoots with opposite leaf pairs.
May–June (Late spring)
· 0.5–1.5 mVines lengthen and climb over nearby plants and fences.
Rapid climbing, tangling growth.
June–August (Summer)
Small dark star-shaped flowers appear in the leaf joints.
Tiny pink-brown to maroon star flowers.
August–September (Late summer)
Slender pods form and split open to release fluffy, wind-borne seeds.
Bean-like pods releasing fluffy seeds (milkweed-style).
October–winter (Dormant)
Vines die back to straw-coloured tangles; roots survive underground.
Dead tangled stems; persistent root crowns.
Growth-stage photo gallery
Photos of dog-strangling vine at different growth stages — note the visual features described under each one to identify it confidently.
New vegetative shoots arising from the crown roots in early June, before twining.
A flowering plant showing the paired (opposite) leaves as the vine climbs and twines.
Patches of flowering plants along a trail in mid-June — it forms dense colonies.
Small star-shaped maroon flowers with darker, lobed centres.
Maroon flowers alongside slender bean-like pods that split to release fluffy seeds.
Click any photo to enlarge. Image source: Ontario weed-identification reference (OMAFRA / Ontario CropIPM).
How to remove it safely
Safest resident-friendly approach
Dig out the root crowns with a spade for small infestations — removing the root is essential because cutting alone won't kill it. Just as important, clip off and bag the seed pods before they open, so the patch can't spread by seed.
Tools & protection
- Gloves
- Spade or garden fork
- Bags for seed pods
Best time of year
Dig roots in spring or early summer; clip seed pods in August before they split open.
Monitoring
Check the area for new shoots through the season and for several years afterward.
Prevent regrowth
Remove pods every year before they open and keep digging root crowns; replant with dense native plants to compete.
What not to do
- Don't just cut the tops — it resprouts from the roots
- Don't leave pods on cut vines; they can still ripen and release seeds
Disposal
Bag vines, roots, and especially seed pods and put them in the garbage. Do not compost, as seeds and root fragments can survive.
Safety cautions
- Wear gloves; the milky sap can be mildly irritating to skin
- Bag seed pods carefully so seeds don't escape on the wind
When to get professional help
Large colonies, especially near ravines or natural areas, often need professional or coordinated stewardship efforts over multiple years.
Bag all plant material — vines, roots, and seed pods — for the garbage. Never compost dog-strangling vine.
Sources
Report a prohibited plant
Found this plant growing on a property? Report it to the City through official Toronto 311.
Report through Toronto 311This page is provided for general educational and reference purposes only. Plant identification results are not a legal determination. Always confirm prohibited plant information using official City of Toronto resources. For hazardous species or large infestations, consider seeking professional advice.
Image credits & usage
Plant photographs are reproduced for non-commercial public education and identification reference only. Sources include Ontario weed-identification (OMAFRA / Ontario CropIPM) and invasive-species fact-sheet materials; all image rights remain with their respective owners. If you are a rights holder with a concern, please contact us through the Feedback page. Photos on this page: Ontario weed-identification reference (OMAFRA / Ontario CropIPM). Contact us.