Answer: If you have the bulbous Dutch iris, you can dig them after they've finished flowering and store them until autumn, when they should be replanted. If yours are bearded or rhizomatous irises, the best time to dig and replant is late summer. I that presents too much of a wait, you can cut the flowering stalks back when the flowers are spent, then dig and divide right after flowering. While you're moving them, you might go ahead and divide them, cutting the foliage and roots back to about 6" and breaking or cutting the vigorously growing ends from the old, dead centers of the rhizomes. Toss the old centers and replant the ends. When replanting the new divisions, amend the bed with plenty of organic matter and plant the newly divided rhizomes so they are just below soil level. Then mulch all around the plants to help the soil retain moisture and to help suppress weeds.
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