Most of my irises are in the ground. I do have some that live in wheelbarrows, old tubs and buckets, and a few in pots. I was thinking about getting them all in-ground just in case I could not water them and they would perish. Then the flood waters rose and the in ground ones are the ones I lost. The others are doing fine.
There is no perfect solution so I guess it is what works best for each one of us. I do like being able to bring a pot of beauty up to the front entrance where every one can enjoy it and then trading it for another pot when the bloom fades.
I guess my point is to make sure the pot is a big one and if it does not have a saucer then put the drainage holes in the side of the pot an inch or so above the bottom. I like the lightest shade of pots I can find and I like them to be uniform in color, shape and size when possible.
