Keep in mind that cannas are going to grow much taller and
multiply more rapidly that your irises. You might consider planting the cannas
behind or at least leave plenty of space between plants if they are intermixed.
Kent

I would not do that, or plant anything else with Cannas. If they are hardy in the ground where they are, they will never stop creeping sideways.

Which way is sideways for a canna tuber? You bring up an interesting point because my canna area is definitely spreading faster in one direction than in the other direction 90 degrees to it. So it seems the tuber knows what is the right side but is there a way we can be sure when we plant so that we can judge how it might grow?