I’ve had iris for several years, but they didn’t seem to bloom as much this year as usual. Any suggestions? GM

There are some 200 to 300 varieties of Iris, but I am guessing you are talking about the most popular variety: Bearded Iris.

As the story goes, Iris get their name from Greek mythology. Iris is the goddess of rainbows and is the messenger to the gods bringing messages from them to humans. Iris also served nectar to the gods and goddesses. She was even part of the story in Homer’s Iliad. How the connection was made to the flower, who knows, but Bearded Iris are beautiful, easy to grow, and pretty drought tolerant. Deer don’t seem to like them much either, so if you have problems with deer eating your landscape, you might want to consider adding Iris to your garden.

If you used to have beautiful blooms but not so much anymore, your Iris are probably overcrowded. Bearded Iris have rootlike structures known as rhizomes which grow horizontally underground and are used for food storage. Over time, these rhizomes can get crowded, causing the plants to languish as they compete for resources.

For your Iris to thrive, they need to be thinned out every 3 to 5 years. Thinning is a great opportunity for you to expand your flowers into another area or share them with friends and neighbors. Late summer is the perfect time to divide or thin your Iris.

To thin, cut the leaf blades back to about 4 to 6 inches in length. This will help the plant concentrate on growing roots rather than leaves when they are re-planted. After trimming, remove the entire rhizome clump using a garden fork or spade.

Once out of the ground, you can divide the clump by pulling them apart by hand. They should break apart pretty easily, but you can cut them apart if necessary. A healthy rhizome should be about as thick as your thumb and have a one or two leaves attached as well as some small roots. Larger ones with no leaves should be thrown away. Rhizomes should also be firm. If any feel squishy, throw them away.

When replanting, remember they like full sun and well-drained soil. Also, do not mulch your Iris. Mulch is usually a must in gardens, but mulch tends to retain moisture which can contribute to fungal diseases in Iris. 

Iris have shallow root systems, so when replanting, you only need to dig down about 4 or 5 inches. Make sure the roots are underground, but leave the rhizome just barely exposed to the air. In this case it is better to be too shallow than too deep.

Once you get them re-planted, water them in and you should be good to go.

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.