: Cynanchum nigrum
: Black dog-strangling vine, Louis' swallow-wort
: Grows rapidly over native vegetation; wind-dispersed seed travels long distances.
: Herbaceous perennial, both range from 0.6-1.8 m (2-6 ft) tall.
: Simple, opposite, narrow, oblong to ovate with a pointed tip, dark green leaves with a smooth, waxy coating; emits a pungent herbal smell when crushed.
: Twining; may climb or creep around adjacent plants.
: Small, five-petaled; clustered in leaf axils; slight rotting odor; purple-black; straight white hairs on dorsal surface; peduncles 0.3-3 cm; blooms June through August.
Fruit and seeds
: Seed pod, resemble those of milkweed, pods split open in mid-summer to release wind-borne seeds.
: Native to southern Europe. Found in hardwood forests, shaded woods, open prairies, fields, savannas, roadsides; can tolerate a range of light and soil conditions.
: By seed, vegetatively by rhizomes and shoots from root crown of parent plant.
: Native dogbanes (Apocynum spp.
) have similar seedpods but are not vines.
Monitoring and rapid response
: Monitor disturbed sites and also edges and paths in undisturbed sites; populations most visible in late summer when the leaves turn golden and seedpods appear. Hand-pulling difficult as roots are fragile, digging preferred, remove roots from site. Foliar herbicide treatment provides effective control; cut-stem herbicide application provides slightly less effective control and is labor intensive. Prescribed fire is not effective when used alone and may improve conditions for increased germination; fire may be useful following herbicide application to control seedlings with less developed root systems. Remove and burn seedpods; multi-year monitoring and follow-up required. Please report sightings with GPS positions to Dr. DiTommaso at: email@example.com.
: The Michigan Natural Features Inventory
(MNFI) has partnered with MISIN to provide the information in this fact sheet. Species images and/or information were used with permission from "A Field Identification Guide to Invasive Plants in Michigan's Natural Communities
" and "A Field Guide to Invasive Plants of Aquatic and Wetland Habitats for Michigan