I grew milkweed in 6 inch pots all last summer because I ran out of garden space. They seem to become root bound pretty quickly, but I'm sure they would do okay through the summer.
By the way... what a cute planter! Good luck.

Thx khakitag im ganna give it a try worst thing Id just have to transplant them.

Here is my Anise caterpillar planter ganna plant lots of parsley in this guy.
{{gwi:461307}}

Here is a link that might be useful: more homemade planters

Adorable containers!

Milkweed has very long roots, rather than spreading roots so that container seems good.

Here is a link that might be useful: Moths and butterflies

Angie, I grew milkweed from seed last year, and potted them up in 4 and 5" pots. They are coming back fine this year, so I'll plant them out now. Also, I had one in a 6" pot that I purchased from MON. I thought surely it had died over the winter because of being in such a small pot. But no, it's coming back better than last year! Don't know if this helps, but hope so.

Saturniidaebreeder - do you sell eggs? Lunas, Ios, and promeathea moths are indigenous to Oklahoma and I'd love to try some. I have lots of different host plants. Just wondering. I've raised lots of sphingid moths.

Susan