You are thinking of a completely different plant called milkweed. The monarch butterflies lay their eggs on it and the caterpillars eat it as their exclusive diet, and become poisonous for it. Its not thorny at all but a broad leafed plant that flowers in the spring. Monarch butterflies can eat nectar from many kinds of flowers. It is a native plant and I have plenty of it growing.
https://en.wikipedia.org/wiki/Asclepias.

Interestingly both these plants have very similar methods of spreading their seeds, seeds attached to silky strands that float away on the wind.