Black and Pale Swallow-worts

Black and pale swallow-worts  (Vincetoxicum nigrum, Vincetoxicum rossicum ), also known as “dog-strangling vines,” are perennial, herbaceous vines that grow from 2 to 6 1/2 ft in length.

Origin/Introduction into the U.S.:

Black swallow-wort is native to Europe near the Mediterranean Sea, while pale swallow-wort is native to Ukraine and parts of Russia. Although swallow-worts’ weren’t highly valued as a horticultural specimen, they escaped cultivation in the 1800s’.


  • Swallow-worts aggressively choke out desirable species. They are problematic in Christmas tree plantations, perennial crop fields, pastures, roadsides, disturbed areas, and natural areas.
  • Pure stands of swallow-wort suppress the establishment of other species and interfere with forest regeneration.
  • Related to milkweeds, swallow-worts are toxic to livestock, deer, and monarch butterfly larvae, which are sometimes fooled into laying their eggs on these plants, but their larvae do not survive. Learn more about the impacts swallow-worts have on monarch butterflies.

Habitat: Both species of swallow-worts can be found in mixed hardwood forests to heavily shaded woods.  They also can be found in disturbed sunny areas, prairies, savannahs, open fields, and along roadsides in moist or dry soils.


Pale Swallow-wort (Cynanchum rossicum syn. Vincetoxicum rossicum)

Leaves:  Leaves are opposite in arrangement, oval to wedge-shaped with pointed tips. Generally, the leaves are 2.5″ to 4.5″ long and 2″ to 2.75″ wide, glossy, and medium green in color. In summer, the leaves begin to display a warm, yellow color.

dog-strangling vine, European swallowwort, Vincetoxicum rossicum (Gentianales: Asclepiadaceae) - 5492571

Flowers: The star-shaped flowers are small and fleshy, with 5 pink to reddish colored petals. They are borne in loose clusters and are visible in late May through mid-July.

pale swallow wort pic

Black swallow-wort (Cynanchum louiseae syn., Vincetoxicum nigrum)

Characteristics are similar to pale swallow-wort, but black swallow-wort leaves are dark green, shiny, and larger in size ranging from 3-4″ long and 2-3″ wide. Flowers are dark purple/blackish in color and bloom from June to July.

black swallow wort

 Fruit/Seeds: The fruit is a smooth, slender, pointed pod that looks much like a milkweed pod. The pods are light green in color and are frequently borne in pairs. They are abundant during July and August. Like milkweed, the pods open in late summer, disseminating large numbers of downy seeds. Can produce 2,000 seeds per square yard.

black and pale swallow wort collage

dog-strangling vine, European swallowwort, Vincetoxicum rossicum (Gentianales: Asclepiadaceae) - 5392102


Management Options: 

Prevention: Once established, swallow-wort is difficult to control. Monitor for populations in late summer, when the plants turn golden yellow and pods are present.  Initial control efforts should concentrate on plants in sunny areas since they will produce the most seeds. Stay out of infested areas during seed dispersal to prevent seed dissemination to unaffected areas. Likewise, clean boots, ATVs, and other equipment when coming out of infested areas.

Physical/Mechanical Control: Small patches can be dug out by hand. The entire plant must be removed and destroyed. To prevent seed dispersal, pods should be removed before they open and then burned.

Large stands can be managed by consistent mowing when pods are very small  (May-July).  Controlled burning is not effective and may improve site conditions for seedling establishment.

Chemical Control: Triclopyr or glyphosate can be applied to foliage prior to seed set typically in late June to mid-July for our region. The use of surfactants helps herbicides penetrate the waxy leaf coating. Cut-stem treatment with glyphosate is effective but labor-intensive. Use of systemic “Round-Up” herbicide is also effective in removing swallow-wort. Regional response teams have found success using a foliar application of glyphosate (Rodeo, Accord XRT-II, etc.) or triclopyr (Garlon 4 Ultra) at a 2 to 3% solution.

For More Information:

Center for Invasive Species and Ecosystem Health http://www.invasive.org/browse/subinfo.cfm?sub=3398

Michigan Department of Natural Resources Michigan Natural Features Inventory https://mnfi.anr.msu.edu/invasive-species/Swallow-wortBCP.pdf

Photo Credits:
Title photo and second flower photo of pale swallow-wort: The Michigan Nature Guys Blog, http://www.michigannatureguy.com/blog/tag/.

Title photo of pale swallow-wort flower: Early Detection and Distribution Mapping System, http://www.eddmaps.org/AT/distribution/point.cfm?id=2279104.Title photo of black swallow-wort flower: Kansas Department of Agriculture, http://agriculture.ks.gov/images/default-source/pp-priority-pest-list-weeds/black-swallow-wort-flowers.jpg?sfvrsn=0.

Bottom black swallow-wort photo :Les Mehrhoff, http://www.discoverlife.org/mp/20psee=I_LJM18444&res=mx&flags=no_slide_show:glean:.

Flower photo: Rob Routledge, Sault College, Bugwood.org.

Fruit/Seeds photo: John M. Randall, The Nature Conservancy, Bugwood.org.


Prevent the introduction of invasive species into the SLELO PRISM.

Rapidly detect new and recent invaders and eliminate all individuals within a specific area.

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Control invasive species infestations by using best management practices, methods and techniques to include: ERADICATION (which is to eliminate all individuals and the seed bank from an area), CONTAINMENT (which is reducing the spread of established infestations from entering an uninfested area) and SUPPRESSION which is to reduce the density but not necessarily the total infested area.

Develop and implement effective restoration methods for areas that have been degraded by invasive species and where suppression or control has taken place.

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Rob Williams
PRISM Coordinator

Megan Pistolese
Outreach and Education

Brittney Rogers
Aquatic Invasive Species

Robert Smith
Terrestrial Invasive Species