Here in CA, the deer do not bother the irises.
Gophers, however, will eagerly dine on the rhizomes. I once had two patches of 'Arctic Express' mirrored across a path. Suddenly I started losing irises from one of the clumps. We caught the culprit in the act, literally, sucking an iris fan down a hole.
After that, we put irises in
that spot into gopher baskets, but they are imo a real danger as they are a tripping hazard. (I once tripped on one of them, and if someone hadn't been there to catch me, I would have probably whacked my head on a stepping stone, as I was definitely going down.) Moreover, the irises try to grow through the basket, which makes division a nightmare, and it is my gut feel (from observation here) that plants just generally do not perform to their full potential in these things.
Irises in other parts of the garden are
not in gopher baskets, and they seem to do okay. You just need to be aware of what critters are active where, and erect defenses accordingly. (I have read about people lining their beds with wire mesh, and I think that is what I am going to do the next time we replant iris in a potentially hazardous spot. (For that matter, that is what I am planning to do with some hosta.) I don't plan on letting the wire edges stick up, though, as in the case of the gopher baskets.)
As for groundhogs, sorry, no experience here. As they are a burrowing rodent, my kneejerk reaction is to be suspicious of them.... but I Google searched on groundhogs and irises, and at least two sites seemed to indicate that groundhogs don't eat irises (even though they may burrow right under them).
Since we are talking critters, I should mention that last fall a raccoon more or less dug up part of my patch of my sole iris seedling. They didn't eat the rhizomes, and (so far as I can tell) all of the rhizomes that I replanted bloomed this spring, but just an fyi.... critters can be annoying and destructive in other ways, apart from eating things.
Best wishes for you and your irises!
