Black Swallow Wort

Black Swallow Wort

Black Swallow-wort (Vincetoxicum nigrum) is an invasive perennial vine native to Europe. It has dark green, glossy leaves and small, star-shaped, dark purple flowers that bloom in late spring to early summer. This plant poses significant ecological threats as it aggressively spreads via seed, forming dense mats that crowd out native vegetation and disrupt local ecosystems. Its presence can negatively impact butterfly populations, particularly monarchs, as its leaves are toxic to their larvae. Black Swallow-wort thrives in a variety of environments, including forests, fields, and disturbed areas, making it challenging to control. Effective management often requires a combination of mechanical cutting (to control seed production and chemical treatments to effectively kill the plant at its roots.

Keys To Success

Black Swallow-wort disperses its seeds primarily through wind. The plant produces slender, elongated seed pods that mature and split open in late summer, releasing numerous silky-haired seeds. These seeds, equipped with tufts of silky hairs (similar to milkweed seeds), are easily carried by the wind, allowing them to spread over long distances. This effective wind dispersal mechanism enables Black Swallow-wort to rapidly colonize new areas, contributing to its invasive nature.  Managing the plant’s seed production is key to controlling its spread. If herbicide treatments are not possible before seed pod production, cutting back the plant to reset its growth trashing developing seed pods is recommended to keep its continued proliferation at bay.