After the first hard frost of autumn, you should cut back the leaves to about 6 inches. To protect the plants from freezing, mulch the earth around their roots.
You should cut them back right after they finish blooming. Only cut back the stem that the flowers were on , unless you have any tattered or dead leaves. rim only dead or injured leaves and cut off the flower stalks.
The best way to control iris plants is to divide the roots. You can replant them in your garden or give as a gift. Planting needs to be done in late summer or early fall. Just lie the roots along the ground and cover with dirt. Firmly press the ground after planting and give a little water.
At the end of the summer, the plants should be prepared for the winter by cutting the leaves back to about four or five inch fans. Clear out all the dead foliage. If the rhizomes are overcrowded and "bubbling up" out of the ground, dig them up, thin, and then replant. Give the excess rhizomes to friends.