Vincetoxicum rossicum is a flowering plant in the family Apocynaceae. It is a perennial herb native to southern Europe and is a highly invasive plant growing in all of the Eastern United States, in the mid west, and southern Ontario and Quebec in Canada. It has several common names including swallowwort, pale swallowwort, and dog-strangling vine. There has historically been much confusion about the genus it belongs to, with authors placing it within Vincetoxicum and others within Cynanchum, but recent molecular and chemical analyses have shown it to belong in the genus Vincetoxicum. Description Leaves The leaves of the pale swallowwort are larger when they are closer to the stem and decrease in size as they move away from the stem. They are in the shape of an ellipse or an oval and contain smooth margins and major veins underneath. The glossy, dark green leaves grow opposite on the stem and are ovate to elliptical. The flowers appear near the top of the plant and grow on stalks that come from the leaf axils. Flowers The buds of the flowers have a pointed apex and are ovoid to conoidal. Also, petals that are unopened are twisted. The diameter of the flowers is 5–7 mm and they are 5-parted. Some of the petals are 3–5 mm in long and do not have hair. The margins of the petals are 0.05–0.15 mm wide and they are typically translucent. The 5-lobed corona is typically pink, red-brown or maroon, which is the same color as the corolla. The corona is sometimes seen as a lighter pink, orange or yellow. The fruits of the Vincetoxicum rossicum are 4–7 cm long and each flower typically contains two fruits. The seeds of the fruit are oblong and are either concaved or flattened on one side and convex on the other side. The seed color varies from light to dark brown. Each stalk has 5 to 20 flowers. The flowers are dark purple or dark brown. Roots It is a twining vine that grows to heights of . The roots of the pale swallowwort are thick. The rootstalk makes a rhizome shape with its roots. Stems are found intertwined in dense patches of plants. They will grow onto other plants when they are alone in order to have structural support. After a year of growth, the stem turns light brown and resembles a decaying stem and stops growing.