The plants are 2-4 ft. tall with soft pink flowers. There is a white form also. The flower heads are 3 to 4 inches across.
The first photo shows flower details and that the horns are longer than the hoods. For more on the flower structure see Asclepias syriaca (Milkweed - Common) in this gallery.
The second photo shows the lance shaped leaves. The leaves are narrower and not as heavy and coarse as those of the common milkweed.