One reason why I wanted to see this species is because it is known from the Chicago Region, along a few railroad tracks, where it is considered introduced. I wanted to make sure that if I ever ran into it, I wouldn't confuse it for Asclepias syriaca. No way. Look at those hoods! They're enormous - over a centimeter long, in fact. In milkweeds, the hoods are the parts of the flower that arch upwards. The corolla lobes are reflexed. The horns are the incurved appendages coming out of the hoods.
In Asclepias speciosa, the pedicels, peduncles, backs of the corolla lobes, and the upper stems are densely white hairy, another character than can be used to distinguish between this and similar species.