Skip to main content

Invasive Species: Black Swallow-wort

Black Swallow-wort (Dog-strangling Vine)

Cynanchum louiseae (Vincetoxicum nigrum)

*Detected in Michigan*

Report this species:

Use the Midwest Invasive Species Information Network (MISIN) online reporting tool

- Or - download the MISIN smartphone app and report from your phone -


A cluster of dark-purple, star-shaped black swallow-wort flowers hangs on a vine.

Photo courtesy of Leslie J. Mehrhoff, University of Connecticut, 

A dried seed pod is open, showing brown seeds with fluffy, white edges.

Photo courtesy of Leslie J. Mehrhoff, University of Connecticut, 

Black swallow-wort vines cover trees in a forest.

Photo courtesy of Leslie J. Mehrhoff, University of Connecticut, 


  • An herbaceous, perennial vine growing up to 7 feet in length.
  • Leaves are shiny dark-green and oval to heart-shaped with a pointed tip.
  • Small, star-shaped flowers are dark purple with 5-petals and grow in clusters of 6-10 blooms.
  • Seed pods are milkweed-like and full of flat, brown seeds covered in fine, white hairs.

Habitat: Black swallow-wort vines thrive in both shade and sun and are found in disturbed areas along roadsides, pastures, old fields and gardens as well as alvar and along fens.

Native Range: Southwestern and Northern Europe.

U.S. Distribution:  From the Atlantic coast to the Midwest and as far south as Kentucky and Missouri. Also present in Quebec and Ontario.

Local Concern: Black swallow-wort grows rapidly and can cover other vegetation. Seeds are carried on the wind or transported by water. Roots are toxic to mammals, including livestock. Plants are toxic to many insect larvae including monarch caterpillars.  


Black Swallow-wort Invasive Species Alert - Printable PDF

Best Control Practice Guide for Black and Pale Swallow-worts- This document provides in-depth information about black and pale swallow-worts in the state of Michigan, including identification, distribution, management and control options.