Dividing your irises every 3-4 years is important for continual bloom and vigorous and healthy plant growth.
Follow these easy steps:
Dig up the entire clump of rhizomes with a garden fork or split off
individual rhizomes. Try to avoid damaging the roots or the leaves (see
Shake excess dirt off and remove dead material from the clump. Remove enough so that the clump is fully exposed.
Break apart the rhizomes from the clump by using your hands or a knife (see photo 2).
Discard any rhizomes that are spongy, rotten, or have visible insect damage.
Trim the roots to about 2” long (see photo 3).
Trim the leaves down to 4-6”. Trim in at an angle on each side (see photo 4).
If necessary amend the soil of the planting location with bone meal or compost. So long as the soil is light your iris should do fine.
Replant rhizomes so that the top of the rhizome is visible and flush with the soil (see photo 5).
Pack soil firmly and water moderately.
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Things to Keep In Mind:
Sources: RainbowFarms; BHG.com
Work with one clump of iris cultivar at a time, so the rhizomes don’t get mixed up with other cultivars. Be sure to mark leaves immediately with a permanent marker or paint pen with the name or description of the cultivar for reference on the fan of the iris.
If storing the rhizomes, store in a cool, dry location. Irises can survive several months out of ground if properly stored.
It isn’t necessary to soak or wash rhizomes free of dirt if you are just moving them around the garden. Only wash rhizomes if the rhizome will be given away, shipped or sold to the public. If the rhizome has some rot that has been cut away, soak in a light bleach solution before planting.
Amend your soil if it has been a while since you have divided. Iris will often use everything they can get from the soil. Add compost and a balanced fertilizer to the soil to help get your iris off to a good start again.