Clumps of bearded iris should be dug and divided every three to four years to promote vigorous flowering. Use a garden fork to lift an entire clump and separate the rhizomes. Discard the old unproductive rhizomes.
Plant the divisions at least 12 inches apart in a sunny and free-draining location. The rhizomes should sit partially above the soil line. Water them well but infrequently – overwatering will cause the irises to rot.