Certified GKH Gardening Expert
It's best to wait 4 to 6 weeks following flowering to do anything to irises as the leaves need to replenish the rhizome. Do, however, remove the spent flower stalk. They are dormant in late summer to early fall and that is the best time to cut the fans back or dig and divide. When you cut back the foliage, leave 6 to 8 inches of foliage cut in an inverted V shape.