Bearded iris are a staple in the landscape. They offer a burst of color when we need it the most in the spring. Late summer is a great time to rejuvenate your iris beds. Iris spread by underground stems called rhizomes. As they spread they tend to grow on top of neighboring plants.
Before you start to dig out the plants it is best to cut back the fans (leaves) to about six or eight inches off the ground. This will make working with the plant easier. Using a spade dig under the rhizome and slowly pop them out of the ground. You will here some popping and cracking and that is okay. Iris roots are surprising deep.
After you get the plants out of the ground it is best to use a sharpie to mark them if you know the names. This is important if you plan on sharing your plants with friends and neighbors.
If you have ever grown iris you are probably familiar with the dreaded Iris Border. This is the caterpillar of a moth that will do significant damage to any type of iris. The caterpillar at maturity is close to 1 1/2″ to 2″ long creamy white with a pink/blush back. The hatch from eggs in April on dead foliage and move into new growth. You will often see a water soaked areas on the leaves as they move down towards the rhizomes. If you are lucky you can squish the borer in the fans before they reach the rhizomes so monitoring the plants will be key. Once in the rhizome they rhizome they eat the stored starch found within. If left unchecked they can and will destroy an iris collection. Female moths will emerge late August and lay eggs on the dead foliage or debris of the plants so good fall clean up will help prevent an outbreak. Inspect all the rhizomes that you dig up for any signs of the borer and discard those plants. The iris borer will also open up the plant to bacterial diseases that can cause different types of rots.
Once the rhizomes have been inspected and cleaned they are ready to plant. Dig holes deep enough to accommodate the roots but keep the rhizome at the soil surface. They tend to rot if they are planted to deep.
Regular maintenance of iris beds will keep them healthy and continue to thrive for years to come.