Straight from The American Iris Society (www.irises.org/)

Culture of the beardless irises differs somewhat from culture of the bearded irises. They should be transplanted in the fall or in early spring. The roots should never be allowed to dry out while they are out of the ground and they should be watered heavily after transplanting. They should be set slightly deeper than the tall bearded. Japanese iris should be planted in a distinct "depression" in heavy soil to assist in supplying moisture to the plant. Siberians and the Pacific Coast Natives can tolerate light shade but the Spurias, Japanese and Louisianas demand full sun. Louisianas and Japanese require moist conditions during the summer months while the Pacific Coast Natives enjoy a very low humidity and dry soil no matter how hot it may get. All, except Louisianas, should be planted in a permanent spot where they can remain for many years as they resent being disturbed. Louisianas tend to "creep" and therefore, should be tended to every few years. All are heavy feeders and need to be fertilized regularly.