Connecticut Plants
Black Swallowwort
Cynanchum louiseae Kartesz & Gandhi

Black swallowwort was introduced to this country as a garden plant. It is now a common weed, both in gardens and in wild areas. A related plant, pale swallowwort, grows in the same habitats. The plants can be distinguished by the flowers. Black swallowwort flowers are always a very dark purple, nearly black. The petals are covered with fine white hairs, and the petal length is about equal to the width. Pale swallowwort flowers range from a light brownish color to dark red, but they are never nearly black. Pale swallowwort petals are hairless, and they are about twice as long as they are wide.

Black swallowwort is an invasive weed that threatens native plant habitats. More on this topic from Invasive Plant Atlas of New England.

  • Synonyms: Cynanchum nigrum, Vincetoxicum nigrum
  • Family: dogbane (Apocynaceae)
  • Habitat: roadsides, fields, edges of woods, rocky areas
  • Height: 3-6 feet
  • Flower size: 1/8 inch across
  • Flower color: dark purple-brown
  • Flowering time: June to September
  • Origin: Europe
Cynanchum louiseae Kartesz & Gandhi
Cynanchum louiseae Kartesz & Gandhi

The petals of black swallowwort are covered with fine white hairs.