Eastern Forest Threat Center - Black Swallowwort

Black swallowwort is an herbaceous perennial twining vine that grows 3 to 6 ft. in height depending on habitat and available support. Opposite leaves grow 2-4 in. long and are hairless and smooth, oblong to ovate in shape, and narrow to a point at the tip. Purple-black flowers borne in small clusters in the leaf axils have the scent of rotting fruit. Fruit pods are 1 ½ -3 in. long and split open to release tufted, windborne seeds. Black swallowwort can also spread clonally from deep rhizomes. It is found in a wide range of habitats from dry and sunny to shaded and moist, from shallow soils on limestone bedrock to deep well-drained silt-loam soils, and from wooded ravines and talus to alluvial woods, pastures and grasslands. Coastal and roadside infestations are common, indicating a probable tolerance of alkaline soils and a possible preference for calcareous soils. It is found in disturbed areas such as highway, rail, utility and other transportation corridors, limestone quarries, abandoned pastures, and old fields. It can invade natural areas and suppress other plant species by competing for soil moisture and nutrients, light, and other environmental factors.

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