Answer: The rhizomes should winter over okay in an unheated basement. They shouldn't completely dry out, but they shouldn't be kept too moist, either. Check them every 3-4 weeks to make sure they're not shriveling up. You might try spritzing them with water and burying them in peat moss or sawdust for the duration of the winter months. Plant them outdoors as soon as the weather permits.
Best wishes with your iris!
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