Iris are kind of an old school flower in that they are something we probably remember seeing in our grandparents landscapes, but they are still a favorite of many gardeners. Part of their popularity likely springs from the fact that they are pretty easy to take care of and one of the earlier plants to flower in the spring. In addition, if you live in an area where you have trouble with deer eating your plants, deer are not particularly fond of iris so they make a good flowering plant in these situations.

You can trace the name iris back to Greek mythology in which we find Iris as the goddess of rainbows. In addition, Iris was the messenger for the gods, bringing messages from the gods to the humans below.

While we love the flowers on our iris in the spring, it’s not uncommon for these plants to stop bloom if they get overcrowded. Iris grow from a rhizome which is like a continuous underground stem if you will. Rhizomes grow horizontally underground and serve as the place where the plant stores its nutrients. Over time, this growth can cause the rhizomes to get overcrowded, resulting in a little too much competition for resources. Because of this lack of necessary nutrients, the plants either reduce their blooms or stop blooming all together.

If you have had irises for several years and have not thinned them out, you are probably noticing this reduction in blooms. Late July and early August are the best time to thin out overcrowded iris. By thinning now, the plant will have plenty of time to develop a new root system for next year’s growing season.

To start the process, trim the iris leaf blades down to about 4 to 6 inches in length. Once you have accomplished this, you can dig up the rhizomes. When doing this try to dig around the rhizome and then life it up with your trowel or shovel being careful not to damage the rhizome. A garden fork works well for this also.

Once you have them out of the ground, you can begin separating them from one another. As you are thinning out these rhizomes, you’re looking for good, healthy rhizomes that are about as thick as your thumb with at least two leaf blades attached. If they are larger than this or squishy, just discard them.

Once you get them split apart into new plants, you can plant some back where you dug them up and transfer the others to a new location in your garden. Just know that iris like full sun and soil that drains well.

Since iris have shallow roots, you’ll only need to dig down about 4 or 5 inches to replant. You’ll need to make sure all the roots are underground, but the top of the rhizome should have a little bit of exposure to the air. If in doubt, it’s generally better to plant them too shallow than too deep. Once planted, give them a good soaking with your hose. The only thing left to do is look forward to seeing your beautiful iris blooms next spring. Good luck.

You can get answers to all your gardening questions by calling the Tulsa Master Gardeners Help Line at 918-746-3701 or by emailing us at mg@tulsamastergardeners.org. Photo: Tom Ingram