Susan: i'm sorry no one has responded to your question. I suspect that's because no one here has grown irises in a container. I tried many years ago, and they all died when I tried to overwinter them in a container. But, if I were ever to try again, I don't think I would try to grow more than one in a container that size. There is an iris forum where someone may be able to help.

Here is a link that might be useful: click here to go to the Iris Forum