Damage

Pale swallow-wort is a very aggressive non-native species that chokes out desirable species. It is problematic in Christmas tree plantations, perennial crops, pastures, roadsides, disturbed areas, and natural areas. It prefers limestone-based soils. Pale swallow-wort is drought tolerant and will thrive in a wide range of soil, moisture and light conditions. It will not tolerate wet areas. Pale swallow-wort can interfere with forest regeneration. (see Figure 1 below) The wind dispersed seeds are produced in large numbers and can travel a great distance. Once established, pure stands of pale swallow-wort suppress the establishment of other species. (see Figure 2 below) It also changes the microbial composition of the soil. Pale swallow-wort contains toxic substances; therefore, deer and other grazers will not eat it. Since it is a member of the milkweed family, monarch butterflies will lay their eggs on pale swallow-wort, but the larvae do not survive. This is not a turf weed or a problem in annual crops.