Cynanchum laeve is a vining perennial herb native to eastern and central U.S. states and Ontario. Common names include sand vine, honeyvine, honeyvine milkweed, bluevine milkweed, climbing milkweed, and smooth swallow-wort.
Like bindweed and some other members of the Convolvulaceae, Cynanchum laeve is a twining vine with heart-shaped leaves common in roadsides, fence rows, fields, and disturbed areas. However, C. laeve is easily recognized as a member of the Asclepiadoideae by its opposite leaf placement, milky sap and distinctive flowers and follicles ("milkweed pods"). The seeds are wind dispersed and can travel long distances.
Cynanchum laeve is considered a noxious weed in several states, and can be very difficult to eradicate from fields because of its deep, extensive root system. Like many other milkweed species, C. laeve contains toxic cardenolide alkaloids, and is a food plant for the caterpillars of monarch butterflies.
Synonymous plant names include Ampelamus albidus (Nutt.) Britton, Ampelamus laevis (Michx.) Krings, and Gonolobus laevis Michx.