Black swallow-wort is an invasive species on the Prohibited Eradicate List. Plant must be destroyed and transportation, propagation, or sale of these plants is prohibited.
- Black swallow-wort grows in sunny and shady areas, such as gardens, roadsides, wooded edges, quarries, pastures and fence rows.
- It grows in a dense, viny mat.
- Leaves are fatal to monarch caterpillars who mistake it for milkweed.
- The Minnesota Department of Agriculture monitors this invasive species. Please report any black swallow-wort you spot at Arrest the Pest.
How to identify black swallow-wort
Black swallow-wort (Cynanchum louiseae) is an herbaceous perennial in the milkweed family.
- It is a vine with twining stems up to 6 inches long.
- Lance shaped with smooth edges.
- Opposite, dark green, and glossy.
- Star-shaped flowers are 1/8 inch, purple with a yellow center, and occur in clusters at leaf axils.
- Typical milkweed-like pod, up to 2-1/2 inches long, 3/8 inch diameter, and smooth.
- When mature, pods open to release rounded, flattened brown seeds with silky filament at the tip.
- Fleshy with a thickly budded rhizomatous crown just below the soil surface.
Reviewed in 2019