Native Range

Ukraine and Russia

Appearance

Pale swallow-wort is an herbaceous, perennial, twining vine with single or multiple stems growing from an extensive fibrous root system. Stems are erect initially, but as plants mature they twine around adjacent vegetation or each other for support, often forming impenetrable thickets. Vines are typically 2–6½ ft (60–200 cm) long. Stems are green and darken with age. Leaves are opposite and elliptical with a pointed tip and a rounded or heart-shaped base. Small, star-shaped flowers are produced in clusters at leaf axils. Each flower has five fleshy petals that are maroon to pinkish and often twisted at their tips. Fruits are thin pods that often occur in pairs and contain numerous tufted, wind-borne seeds.

Impact

Black swallow-wort grows rapidly, forming dense mats that smother and shade out other species. Large infestations are capable of altering plant communities by displacing native species, interfering with forest regeneration, reducing forage production, changing community structures, and disrupting ecological functions. This species negatively impacts monarch butterflies by replacing the monarch's native milkweed hosts. In addition, because swallow-worts are related to milkweeds, monarchs mistakenly lay eggs on swallow-worts, but larvae hatching from those eggs fail to develop.

Reference

Tewksbury, L., M. Szucs, L.R. Milbrath, R.S. Bourchier, and N. Capuccino. 2023. Swallow-worts (Vincetoxicum spp.): History and Ecology in North America. In: R.L. Winston, Ed. Biological Control of Weeds in North America. North American Invasive Species Management Association, Milwaukee, WI. NAISMA-BCW-2023-30-SWALLOW-WORTS-P. https://bugwoodcloud.org/resource/files/27697.pdf

Resources

• Biological Control of Invasive Plants in the Eastern United States - USDA Forest Service
• Element Stewardship Abstract - The Nature Conservancy
• Weed of the Week - USDA Forest Service
• Weeds Gone Wild: Alien Plant Invaders of Natural Areas - Plant Conservation Alliance
• Plant Invaders of Mid-Atlantic Natural Areas - National Park Service
• Fact Sheet - Ontarios Invading Species Awareness Program
• Best Management Practices - Ontarios Invading Species Awareness Program

Selected Images

Maps

Invasive Listing Sources

• Connecticut Invasive Plant List
• Connecticut Invasive Plant Working Group
• Hoffman, R. & K. Kearns, Eds. 1997. Wisconsin manual of control recommendations for ecologically invasive plants. Wisconsin Dept. Natural Resources, Bureau of Endangered Resources. Madison, Wisconsin. 102pp.
• Indiana Invasive Species Council - Invasive Plant List
• Indiana Terrestrial Plant Rule
• John Randall, The Nature Conservancy, Survey of TNC Preserves, 1995.
• Maryland Invasive Species Council - Invasive Species of Concern in Maryland
• Massachusetts Invasive Plants Advisory Group List
• Massachusetts Noxious Weeds
• Massachusetts Prohibited Plant List
• Minnesota Noxious Weeds
• National Park Service, Mid-Atlantic Exotic Plant Management Team Invasive Plant List
• National Park Service, National Capital Region Exotic Plant Management Team Invasive Plant List
• New Hampshire Invasive Species Committee. 2005. Guide to Invasive Upland Plant Species in New Hampshire. New Hampshire Department of Agriculture,  Markets and Food Plant Industry Division and New Hampshire Invasive Species Committee.
• New Hampshire Prohibited Invasive Species
• New Jersey Invasive Species Strike Team 2017 Invasive Species List
• New York Regulated and Prohibited Invasive Species - Prohibited
• Non-Native Invasive Plants of Arlington County, Virginia
• Ontario’s Invading Species Awareness Program Tracked Species List
• Pennsylvania Department of Conservation and Natural Resources Invasive Plants
• Pennsylvania Noxious Weeds
• Plant Invaders of Mid-Atlantic Natural Areas
• Rhode Island Natural History Survey
• Vermont Noxious Weeds
• WeedUS - Database of Plants Invading Natural Areas in the United States
• Wisconsin Noxious Weeds
• Wisconsin's Invasive species rule – NR 40

References