When Do You Cut Iris Foliage Back?

Spurias and Siberians

• Remove dead and diseased foliage from these as soon as you see them. Don't wait until their blooms have finished if the leaves die back or you see signs of fungus or bacterial infection. The foliage on Spurias and Siberians can be cut back to the ground after each bloom season has completed. Do not dispose of diseased foliage in the compost heap, to prevent spreading disease.

Japanese

• Remove the old foliage from Japanese irises after the first frosts. Look for any signs of thrips on the foliage, as well as borer eggs. These pests can often be controlled, however it's best to completely destroy the old foliage with these present. Also remove anything that appears diseased. Wait until you plan to divide these -- every two to four years -- then cut back all but one-quarter of the foliage. Plant Japanese iris in a different area than you've grown them previously.

The Bearded Group

• The tall and dwarf bearded varieties can be cut back in a couple of steps. First, when the blooms have finished, you can cut the tall bloom stalk back. Opinion varies as to whether to cut it halfway or fully down to the rhizome, so choose what works best for you. Allowing the leaves to remain awhile longer lets the rhizome receive further nutrients. Then, clip the foliage back in the shape of a fan, using diagonal cuts. Cut them back to 6 or 8 inches for tall varieties, and to about 2 or 4 for dwarf types.

Louisiana

• On the Louisiana group, you'll need to cut bloom stalks after the bloom season, unless you plan to let any of them go to seed. Cut out the dead leaves when they're nearly exhausted, and cut out anything that shows signs of disease or injury. Some Louisiana varieties will remain green until the end of summer, especially if mulched, while others go dormant.