Black & Pale Swallow-worts Black and pale swallow-worts, also
known as “dog-strangling vines,” are perennial, herbaceous,
twining vines that grow from 2 to 6 1/2 ft in length. Native to
Eurasia, these species are adapted to a variety of habitats.
Swallow-worts grow rapidly and once established can completely
smother native vegetation. Related to milkweeds, swallow-worts
are extremely toxic to livestock and monarch butterfly larvae,
which are sometimes fooled into laying their eggs on this plant.
Their wind-dispersed seeds can spread over long distances. Pale
swallow-wort prefers limestone-based soils. It is drought
tolerant and will thrive in a wide range of soil, moisture, and
light conditions with the exception of extremely wet soils.
Swallow-worts aggressively choke out desirable species. They are
problematic in Christmas tree plantations, perennial crops,
pastures, roadsides, disturbed areas, and natural areas. Turf
and annual crops, however, are generally resistant to
infestations. Swallow-worts interfer