You can move them at any time. It is best to wait until after they bloom but if they need to move it won't hurt them. I had one die and because I was supposed to have a garden tour I popped another iris out of a pot and into it's spot in early March (thought fans would look better than an empty space). It was happy with it's new home and bloomed. You should be past hard freezes by now so May and June would be great planting times.
