How to transplant irises

Q. Can I still transplant my irises? I just cut them back and they are really thick!

Don from Canfield

A. Yes you can. Barb Delisio, OSU Extension Master Gardener, provides us with the details:

Hurry because August to mid-October is the best time to do it. Usually irises should be dug up and separated every three to five years.

Once the rhizomes (roots) of the iris have produced a bloom, they will not bloom again. Only the new rhizomes that form along the edge of the old one will produce flowers the coming year.

The first thing to do is to cut the top leaves off to about 3 to 4 inches high. You’ll need these leaves later to decide where to divide the clumps.

When you begin to divide the clump, use a garden spade or fork to dig up the clumps. Begin loosening the roots along the outside edge of your grouping, prying upward with each cut.

Shake as much soil off the clumps as possible. Then use the force of a stream of water from your garden hose to wash away remaining soil. Once all or most of the soil is gone, you can see the old, dried-out rhizomes and the strong good ones. Cut the old dried-out rhizomes away from the solid, growing rhizomes, which should have the leaves of this past year’s plant. Put them in the trash.

Save the good rhizomes that have four to five leaves in their fan. The area in which you are planting your new rhizomes should have at least six hours of direct sunlight a day. Make sure the area is drained well and properly fertilized. Avoid high-nitrogen fertilizers for they can promote bacterial soft rot in bearded iris rhizomes.

When you plant the iris, make sure the top of the rhizome is level with or just slightly below the soil surface. Do not mulch directly over rhizomes because mulch tends to retain too much moisture and may rot the rhizomes. Water the rhizomes deeply right after planting and once a week for a month.

Eric Barrett is OSU Extension educator for agriculture and natural resources in Mahoning County. Call the office hot line at 330-533-5538 from 9 a.m. to noon Mondays and Thursdays to submit your questions.