I keep chickens and there might be a good reason the hens are scratching and pecking at your iris: IRIS BORERS. I had a terrible problem with these pests until my hens got in the bed and gave it a good going-over. NO MORE BORERS. They ate the eggs in the soil and in the summer they turned over some of the infested rhizomes and dug out the borers themselves. They may be doing you a favor....
If you want to keep them out of a bed, lay a piece of chicken wire OVER the bed, weighted down around the edges here and there with rocks. They won't be able to scratch and once stuff starts to grow up thru the wire, you can decide to either remove it or leave it in place. Hope this helps keep the hens out of the stew pot!
