I have it and the Monarch caterpillars do eat it. They actually prefer it to the tougher leaves of the common milkweed. It’s an annual for me, but for the past couple of years I always have some seedlings coming up. Funny looking plant. Last year I had one looking kind of like the Charlie Brown Christmas tree. Pretty much a tall stick with a bunch of seed balls. Wish I could find the picture I took.

Ralph, the milkweed we got from the fall swap was labelled 'Family Jewels", which would correspond to Gomphocarpus physocarpus a.k.a. Asclepias physocarpa. However, it seems that Gomphocarpus fruticosus looks similar so we may have to look closer at the flowers and fruits to tell them apart. BTW, ours has so far produced only small flowers - indeed on a tall stick, but no family jewels yet (wink, wink).

Well, mine was labeled “hairy balls”. All I have is a close up of the seed balls from last year. Flowering now, but I didn’t take any pictures yet.

The difference between G. physocarpus and fruticosus is well described here:

"The difference is that G. fruticosus is a smaller plant than G.
physocarpus and the seed pod is shaped a little different. For G.
fruticosus, the seed pod is slightly oblong and can resemble a swan
which is where the name “Swan plant” came from. G. physocarpus has a
seed pod that is more rounded and thus became known as “Balloon plant”.
Now the two common names of “swan” and “balloon” plant are interchanged
between both species."

Mine must be physocarpus then. It is currently 6 feet tall and has round spiky seed balls. I plan to save seeds and plant it for the Monarch caterpillars next year.