Answer: After the flower stalks finish blooming they may be cut back. Foliage, however, should be left on the plant as long as possible to allow the plant to store up carbohydrate reserves for future growth and bloom.
Most types of iris should not be trimmed back in your location until the foliage dies back in winter. If you are growing a type of iris who's foliage turns yellow and begins to fade away this summer, then you can trim it back at that time.
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