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CommentsPrairie Milkweed (Asclepias sullivantii) somewhat resembles Common Milkweed (Asclepias syriaca) in appearance, but the former species has flowers that are slightly larger in size and its leaves are hairless on their undersides. Prairie Milkweed is usually a shorter plant than Common Milkweed, and it produces fewer umbels of flowers from the axils of its leaves. Another similar species is Purple Milkweed (Asclepias purpurascens). This latter species differs by having seedpods that are always smooth (rather than bluntly warty) and it has short hairs on the undersides of its leaves. In addition, the flowers of Purple Milkweed are slightly smaller in size than those of Prairie Milkweed, and they are usually more purple. Sometimes Prairie Milkweed has difficulty in forming seedpods because many flower-visiting insects are not very effective in removing and transferring pollinia from one plant to another. In addition, it is not uncommon for some of these insects to become entrapped on the flowers and unable to escape. Another common name of this plant is Sullivant's Milkweed.