My best specimen Rex at the moment is my species B. rex. It's in a large azalea pot, clay, that I would guess is at least eight inches and probably more. It's dark out there and I don't wanna go look! I like to use clay 'bowls'--don't know what their proper name is, but they're bowl-shaped terra cotta and come in a lot of sizes (but right now I have more that are broken than are whole!) and sometimes ones that either seem tough or that seem to dry out too fast I put in plastic bulb pans. I don't ever grow them in standard pots, partly because I just don't think they look as good, but partly because I was told many years ago that I shouldn't (I tend to be a 'good girl' who does what I'm told, if I'm told by someone who knows what they're talking about!) They are shallow-rooted plants and there is some danger of soggy soil in a deeper pot which could cause root-rot. They will need to have old rhizomes removed every year or so to make really good specimen plants--you can just prune that out or re-pot at that time.

WOW! I'll bet an 8" pot of your species Rex is a sight to behold,Greenelbows. So, I take it the old rhizome eventually becomes non-productive and can be pruned off/out and discarded? judy

Yeah, or you can use it to propagate more. I remember visiting the local university's greenhouses a couple times when they'd been repotting rexes and other rhizomatous, and the wastebaskets would be completely filled with old rhizomes. Don't recall if I took any (with permission, of course--I'm really square!)