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The best time to move iris is six to eight weeks after they bloom. Division and transplanting can be done at the same time. I would try to flag them now with some type of marking system while in bloom so that you know what you are moving later.
You will want to dig and divide them every 3-4 years to remove the old rhizomes in the center of the clump that won't bloom again. This is usually done in August or September . Siberian iris can be fertilized in early Spring and after bloom with regular fertilizer (like 10-10-10). They like even moisture through the growing season. You don't have to remove the bloom stalks if you don't want to, or if you want them to reseed. After the leaves die back, cut them off a few inches above the ground. * Apply a thin layer of compost around the base of plants each spring, leaving the rhizome exposed.