Answer: Beardless, or Japanese Iris will perform better in clumps than other types of iris, but after a while, they all need to be divided. You can divide in the fall or in the spring by digging rhizomes and cutting or breaking the clump apart. Keep the fibrous-rooted rhizomes moist during the process of digging and replanting. Plant rhizomes 2" deep and 1 1/2' apart in a bed freshly amended with organic matter. Japanese iris demand moist conditions during their growing and flowering period and aged compost or peat moss will help the soil retain moisture.
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