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Home > Plants, Pests & Pest Control > Bad Plants > Black Swallow-wort

Black Swallow-wort

Small, nearly black flowers hang in clusters at nodes.Common name: Black swallow-wort, Dog strangle vine
Scientific name: Cynanchum louiseae

Description: Black swallow-wort is an herbaceous perennial in the milkweed family. It is a vine with twining stems up to 6 feet long with dark green, glossy foliage. The lance-shaped leaves are opposite with smooth edges. Flowers are 1/8 inch, purple with a yellow center, star shaped, and borne in clusters at leaf axils. Fruit is a typical milkweed-like pod, 2-2 1/2 inches in length, 3/8 inch in diameter and smooth skinned. Like native milkweeds the seed is readily spread by the wind. Roots are fleshy with a thickly budded rhizomatous crown just below the soil surface.

Impacts: Black swallow-wort is difficult to control and has been noted to invade prairie areas. Stands can eventually cover several acres of land and exclude native vegetation.

History: Black swallow-wort is native throughout central and southern Europe and Asia. It was introduced into North America as a horticultural plant that quickly escaped cultivation. Today it is common throughout the eastern U.S., but it is also present in the Midwest and has been observed in Wisconsin, Iowa and South Dakota. The only known established population in Minnesota is being eradicated.

Habitat: It readily invades disturbed sites and managed landscapes. Black swallow-wort is commonly found in old fields, pastures, and fence rows.

View black swallow-wort distribution


Vines smother out surrounding vegetation. Smooth slender mildewed-like bods hand in pairs at leaf axels.

More Information

New Invasive Plants of the Midwest Fact Sheet: Black Swallow-Wort Cynanchum louiseae (pdf)


Click on pictures to see larger images to help further identify black swallow-wort.

Black swallow-wort flower
Black swallow-wort flower.
Black swallow-wort leaf  Black swallow-wort leaf
Black swallow-wort leaves. Notice the variation in leaf shape.
Black swallow-wort plant
Black swallow-wort plant.

Photos by Minnesota Department of Agriculture

If you suspect you have seen this plant in Minnesota:

Arrest the Pest Hotline
1-888-545-6684 (toll free)