Green milkweed is perennial from a vertical rootstock.
Stems are mostly solitary or in pairs, and are up to two feet tall. Leaves are usually opposite, up to four inches long, and extremely variable in shape. Plants from dry sites tend to have long narrow leaves, whereas those from moist sites are nearly round. About 20-80 pale green flowers occur in clusters. These are about two inches in diameter and are found in the upper leaf axils.