Not sure what would work..You dont want anything that would hold moisture next to the rhizome, which would promote rot..Something drought tolerant might work well. Try it you really dont have much to lose.

I've never grown bearded iris (assuming that's what you mean) in pots, but they're awfully hardy, I can't imagine much would give them issue.

dbarron- beardeds are hardy (withstanding freezes) but they are susceptible to rot in moist conditions as littlebit says. Keeping any groundcover off the tops of the rhizomes will help prevent rot. Succulents should work as they will accept the dryness between soakings.

If you have historics they are much more forgiving.

I guess having lived in Oklahoma and Arkansas, they mostly just grow and few are the ones I've ever seen rot in any siting.

However, we're probably in an ideal climate for them, with little rainfall during the mid to late summer dormancy.

We have no summer rain either. I've only experienced rot once. PU.