Signs You Need to Transplant Iris
There are a few signs that you should consider dividing iris plants. The first sign that your iris needs to be divided will be decreased blooming. Overcrowded iris rhizomes will produce fewer flowers than uncrowded iris rhizomes. If you have noticed that your iris are blooming less than they usually do, you may need to transplant the iris in your garden. The next sign that you should consider transplanting your iris is if the rhizomes start heaving out of the ground. Overcrowded iris rhizomes will start to push on each other, which results in the entire root system of your iris plants literally pushing themselves out of the ground. The iris roots may look like a mass of snakes or a pile of spaghetti when they need to be divided. They may even stop putting up foliage and the plants may only grow foliage on the outside edges of the clump.
When to Transplant Iris
The best time when to transplant iris is in the summer, after the iris have finished blooming, up until fall.
Steps for Dividing Iris Plants
To divide your iris, start by lifting the clump of iris plants out of the ground with a spade or fork. If possible, lift the whole mass out whole, but if you are unable to do this, carefully break the clump into smaller parts and lift these out. Next, brush of as much dirt as possible from the iris rhizomes. This will make it easier to see when you are breaking the clumps apart. The next step in dividing iris plants is to divide the iris rhizomes. Each iris rhizome should be divided into pieces that are 3 to 4 inches long (8-10 cm.) and have at least one fan of leaves on the rhizome. Do not remove the roots from the rhizomes. As you get closer to the center of the clump, you may find large sections of rhizomes that have no leaf fans. These can be discarded. Check all of the divided iris rhizomes for iris borers and disease. The iris rhizomes should be firm and not soft. If the rhizome feels soft, throw it away.
Steps for Transplanting Iris
Once the iris rhizomes have been divided, you can replant them. First, trim all of the iris leaf fans back to about 6 to 9 inches tall (15-23 cm.). This will allow the plant to re-establish its roots without having to support a large amount of foliage at the same time. Next, plant the iris rhizomes in the selected location. This location should receive a good deal of sunlight and should be well draining. Dig a hole where the rhizome will settle into the ground just below the ground level. If planting several iris near each other, point the rhizomes away from each other and space them 18 inches (46 cm.) apart. Spread the roots out around the rhizome and then cover the roots and the rhizome with dirt. Water the newly transplanted iris plants well.
