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Leaf and bud of pale swallow-wort. Photo by Rob Routledge, Sault College, Bugwood.org. -
Flowers of pale swallow-wort. -
Green seedpod before it dries, opens, and releases seeds. -
Infestation of pale swallow-wort. Photo by Rob Routledge, Sault College, Bugwood.org. -
Leaf is oval shaped with a pointed tip. Photo by Rob Routledge, Sault College, Bugwood.org. -
Dried seedpod of pale swallow-wort. Photo by Leslie J. Mehrhoff, University of Connecticut, Bugwood.org.
Common names: Pale swallow-wort
Scientific name: Cynanchum rossicum Kleopow
Legal status
All above and below ground parts of the plant must be destroyed. Additionally, no transportation, propagation, or sale of this plant is allowed. Failure to comply may result in an enforcement action by the county or local municipality.
Background
Pale swallow-wort is a vining herbaceous plant in the milkweed family. Originating from southwest Russia and Ukraine, pale swallow-wort was introduced to the United States in the late 1800s as a cultivated plant. Since then, it has spread throughout the eastern United States and parts of the Midwest, as well as southern Ontario and Quebec in Canada. In 2020, two populations were discovered in Scott County, Minnesota. Both populations are reproducing and spreading into adjacent areas.
Description
- Pale swallow-wort is an herbaceous, twining perennial vine growing up to 7 feet long.
- Leaves are oval to heart-shaped with pointed tips. They are shiny and medium green to yellow.
- Flowers are small, star-shaped and pale pink to reddish brown, with five petals. Flowers grow in clusters of 6 to 10 blooms.
- Fruits are typical milkweed-like pods full of flat brown seeds covered with fine white hairs.
- Unlike black swallow-wort, pale swallow-wort does not have rhizomes. It grows in clumps with multiple stems.
Habitat
Pale swallow-wort is an herbaceous vine that is tolerant of shade, sun, and a variety of soil conditions. It is commonly found in disturbed areas including old fields, woodlands, and brushy areas.
Means of spread and distribution
Pale swallow-wort seed can be spread by wind, allowing long-range dispersal. It can also spread by mowing or soil tillage that breaks up root pieces and moves them to new locations.
Impact
Pale swallow-wort forms dense and extensive patches that suppress native vegetation. This disrupts local ecosystems by reducing species diversity and wildlife habitat. Infestations can eventually cover several acres of land and the tangled vines form impenetrable thickets. Often, the vines are not noticed until they are well-established and difficult to control.
Pale swallow-wort may also have a negative impact on monarch butterflies as the plant is toxic to many insect larvae. Since pale swallow-wort is in the milkweed family, female monarchs will lay their eggs on pale swallow-wort, but they have a strong preference for common milkweed. Pale swallow-wort can also displace common milkweed, reducing habitat for monarchs.
Prevention and management
- Do not plant pale swallow-wort.
- Dig up or pull the entire plant, including roots, once or twice per growing season.
- Mowing is not recommended as it can spread seeds and root fragments.
- Plants can also be controlled with either foliar or cut-stem herbicide applications. For specific herbicide recommendations, contact your University of Minnesota Regional Extension Educator.
Toxicity
Pale swallow-wort is suspected to be toxic to mammals, including livestock.
