Tall Green Milkweed is one of the lesser known species of milkweed that is occasionally found in upland prairies. It is distinguished primarily by its greenish white umbels of flowers, lack of horns in the hoods of the flowers, and narrow alternate leaves. It also produces more umbels of flowers per plant than most milkweeds. Other milkweeds usually have opposite leaves. A somewhat similar species, Asclepias viridiflora (Short Green Milkweed), is a shorter plant with pairs of opposite leaves. It produces only 1-2 umbels of flowers that nod downward. Another similar species, Asclepias verticillata (Whorled Milkweed), is a smaller plant with whorls of grass-like leaves; these leaves are more narrow (filiform-linear) than those of Tall Green Milkweed.