Terrestrial invasive species

Nature

Most of these invasive plant factsheets are created from the booklet Minnesota invasive non-native terrestrial plants, an identification guide for resource managers.

Check the additional resources and herbicides table for more information.

Black swallow-wort- Early Detection Species

Black swallow-wort is considered a early detection species not present or with a limited distribution in Minnesota.

photo: Asian long-horned beetle

Description:

Appearance: Perennial, herbaceous vine in the milkweed family.  Vines can grow up to 6 ft long.  

Leaves: Opposite, lance-shaped, with smooth edges.

Flowers: Purple flowers with yellow center, five petals with small hairs on the petals, flowers arranged in clusters from the leaf axils.  Flowers from late May to mid-July. 

Seeds: Seeds are in milkweed seedpods 1.5 - 3 inches long.  Seed pods open in late summer and early fall and release wind-borne seeds on silky filaments.

 

Ecological Threat:

  • Grows aggressively and forms dense patches that can cover other species in forests, grasslands, and savannas. 
  • May have negative impacts on monarch butterflies by displacing the native milkweeds upon which monarchs' depend.  Additionally, swallow-wort may serve as a fatal host to monarch larvae.  When monarch butterflies lay eggs on black swallow-wort, the butterfly larvae are unable to develop on black swallow-wort and die.   It is unknown how large of impact this has on monarch populations.
  • Black swallow-wort is a MDA Prohibited Noxious Weed (Eradicate List) in Minnesota meaning that above and below ground parts of the plant must be destroyed.  Additionally no transportation, propogation, or sale of black swallow-wort is allowed.

Report Black swallow-wort by emailing "Arrest the Pest" arrest.the.pest@state.mn.us or calling 651-201-6684 (metro) or 1-888-545-6684 (toll-free)

 

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