First and third look right as rain. Not sure about the middle since I’ve never grown it. It looks worthy of a pot and soil.

Thanks for the answer. Do you think they would survive winter in a pot outside in zone 7b/8a? Or should I plant them in the ground?

They are pretty hardy but the ground is always better than a pot. I have lost some Asclepias that we’re in pots but never any in the ground.

Thanks. Do you think they would survive winter in a green house?

Yeah, I often left a couple dozen seedlings in the gh over the winter, but I let mine get pretty cold. What was your min gh temp?

I haven't built my green house yet but will start building it in a few weeks. When it is built I will put all my asclepias in it. How hot does it have to be in a greenhouse to keep the plants alive.

32F.