You may have to start with a small pot first and pot up as the plants grow. I find they do much better in pots than in the ground, especially if elevated off the ground, but of course you will have to water them every day if you grow them this way. I have had some growing in 8 inch pots that have not gone into dormancy, yet all the ones in the ground have. The seedlings could be a bit soft before they develop their tubers. I use a very open, free draining potting mix with lots of perlite added. It holds enough moisture for a day, but drains very freely. They seem to love this.
Hope this helps, and I'm glad to know the progeny are still multiplying!