I have never heard of voles eating iris. I don't have many iris, but haven't seen any damage. I don't know why I can leave a hosta or a lily bulb laying on top of the ground and voles don't eat them, but the minute you plant them, - they eat them - lol. This year, the voles also ate the roots of some of my sedums, and people are telling me they are eating astilbe roots.
