Out of the seed I got last year, I have three hearty little redring seedlings in a tray that are about three inches tall right now and need transplanting. Since they are so small, I'm kind of fearful of planting them out in my open grass prairie area that I have common milkweeds growing in for fear of losing them while so small.

Is it possible to grow them in containers? If so, how big of containers do I need? I have 5 gallon buckets, a couple 3-5 gallon nursery pots, and a couple three foot tall narrow garbage cans that I use to container grow horseradish that I can use if the buckets or pots aren't suitable. I'm not sure how deep of a taproot the redring milkweed gets.