You can cut the spent bloom and its stalk if you feel you need to. It's not really necessary though. You can also cut any damaged or yellowing leaves. If you do cut, cut them just above the rhizome. Don't cut any healthy, green leaves though. Don't disturb the rhizomes by which the Iris propagates. The best blooms will occur between years 2 and 4 after original planting. After this the quality diminishes and they shoud be dug up, separated and replanted...