Answer: I wonder if your iris leaves are being "chopped down" by slugs or snails--since they tend to come out at night, it makes sense that you have not seen them. To deter slugs, remove any dead leaves and debris around your planting. Don't mulch your bed--mulch provides a perfect hiding place for slugs. You might try sprinkling diatomaceous earth around and under your plants--though you will have to reapply this after any rain. And, of course, you can go outside at night with a flashlight and hand-pickthe critters!
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