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Pale swallow-wort (Vincetoxicum rossicum)
Herbaceous, perennial vine that twines 3-6’ tall with small hairs on the stems and spreads vegetatively and reproductively. Dies back in the winter.
Pale swallow-wort is Prohibited (Red counties)
Other names for this plant include:
- Common names: European swallow-wort
- Scientific names: Cynanchum rossicum; C. medium; V. medium
- Invades the understory of forests, woodland edges, grasslands, and old fields covering native vegetation and forming dense thickets. Tolerant of sun and shade.
Classification in Wisconsin: Prohibited
Species Assessment Groups (SAG) were assembled to recommend a legal classification for each species considered for NR 40. The recommendation for pale swallow-wort was based upon this literature review developed by the department.
Leaves: Opposite, oval, and smooth. Dark green and shiny with pointed tips and short petioles; 2-5” long.
Flowers: Pale swallow-wort has maroon to pale pink flowers and petals that are twice as long as wide and are hairless. Umbel-like, branched clusters have 6-10 flowers that bloom June-July.
Fruits & seeds: Slender pods, similar to milkweed, are 2-3” long, form late July-August, and turn from green to light brown or golden as they mature. Seeds are flat and attached to thin filaments that aid in wind dispersal, similar to milkweed.
Roots: Root crown fragments support dormant pale swallow-wort buds that resprout if not damaged. Does not have rhizomes; creeping perennial roots.
Similar species: Black swallow-wort (Vincetoxicum nigrum; invasive) is very much the same with the exception of the flowers. Black swallow-wort has dark purple flowers with petals that are the same length on all sides and are hairy.
Counties in WI where pale swallow-wort has been reported (as of July 2011). Both vouchered and unvouchered reports included.
Currently, there have not been reports of pale swallow-wort in WI. Have you seen it? Send us a report.
If the entire infestation cannot be treated focus on plants that are growing in the sun because they produce many more seeds than plants in the shade.
Mechanical: Remove all seed pods before they open and either burn or dispose of in a landfill; most effective if done in mid-July. If plants are dug up, all root fragments and root crown must be removed before seeds ripen.
Chemical: Cut-stem treatment with glyphosate. Foliar spray or wicking in August-September with either triclopyr ester or glyphosate and a surfactant after the infestation is mowed and new growth has formed. Foliar treatment should begin after flowering, but before seed production.
View pale swallow-wort pictures in our photo gallery!
Sources for content:
- Czarapata, Elizabeth; Invasive Plants of the Upper Midwest: an illustrated guide to their identification and control. University of Wisconsin Press. 2005. Pg. 132-133
- Plant Conservation Alliance's Alien Plant Working Group. Weeds Gone Wild: Alien Plant Invaders of Natural Areas. Pale Swallow-wort
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