Things You'll Need
Sharp knife or plant clippers
Sterile straw or salt hay
Iris plants are hardy perennials. The rhizomes are planted at the surface of the soil with the roots buried deeply in the flower bed. When the bed is well prepared and conditioned the iris plants rarely need any form of mulch or winter protection. Decaying leaves and detritus must be cleared away to prevent contamination of the plant bed. You have made an investment in purchasing and preparing a perennial garden. You have enjoyed the large colorful blossoms, and it is important to properly winterize the iris plants in your garden.
Cut back the leaves and stems of your iris plantings with a sharp knife or clippers after the leaves have turned yellow and become droopy. Leave the green growth intact as this is crucial to plant survival. The best time to do this is after the first frost in September or October.
Clear the iris bed of all plant debris including leaves and decaying matter.
Mulch the iris plant after the ground freezes with only one inch of sterile straw or salt hay in a zone where the frost will heave the rhizomes up and down. Iris in warmer areas are better without mulch.
Remove the straw or hay mulch immediately if the weather begins to warm up.
The green leaves must be left attached to the rhizomes as they are collectors of nutrients for the next growing season.