A tough invasive to swallow.

Black swallow-wort (Cynanchum louiseae) is an invasive perennial vine that can grow up to 8 feet tall. If it has nothing to climb on it will tangle around itself creating thick ropes which makes its common name – “dog-strangling vine”- understandable. Black swallow-wort has opposite green leaves and small purple five-petaled flowers. It produces long green pods in late July like other plants in the milkweed family. Seeds from these pods are dispersed by the wind. 

Black swallow-wort can grow in sun or shade and is allelopathic which means its roots release a compound that inhibits the growth of nearby plants. Black swallow-wort can also be harmful to Monarchs as they sometimes lay their eggs on the milkweed look-alike only to have the larvae starve once they hatch.

Black swallow-wort is difficult to control. If you plan to dig the plant up, make sure you get as much of the root crown and rhizomes as possible otherwise it will re-sprout. Bag the plants and dispose of properly as seed pods can still form even when out of the ground.