Well, mine aren't in 5 gallon buckets, but they are in planters, which is kind of the same thing. And they're doing just fine. One rhizome per planter as you suggested.
They will be going in the ground eventually. I just have to win the war with the vines that the previous home owners planted around my pergola.
Bottled: Oatmeal Porter, Double Chocolate Chipotle Porter
Kegged: IPA, Red Rye