Swallow-wort is the single most aggressive terrestrial invasive species found in the Eastern Lake Ontario region and elsewhere in New York and the lower Great Lakes. Native to the Ukraine and southern Russia, this plant is responsible for preventing forest regeneration, interfering with Christmas tree plantations, crop fields, pastures, and valuable natural areas. It also interferes with insect populations and bird populations with specialized feeding habits.

Significant monetary and technical resources continue to target the management of swallow-wort. Over the years, numerous best management practices have been the focus of attention for land managers. Some BMP’s include, herbicides, smothering, burying, and mowing. Recently, a biological control has been approved in the U.S. for use on swallow-wort populations and new studies are underway to develop additional biological controls for this species.

Black Swallow-wort
Pale Swallow-wort

Black and pale swallow-worts (Cynanchum louiseae, Cynanchum 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 U.S.:
Black swallow-wort is native to Europe near the Mediterranean Sea, while pale swallow-wort is native to the 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.

Habitat: Both species of swallow-worts can be found in mixed hardwood forest 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.