Irises are a popular perennial plant that can bring pleasure to your garden for many years with little care. However, periodic division is an important cultural practice for maintaining plant health. When to divide the iris is a common question among gardeners, and the answer is that it should be done approximately every three to five years. Late July to mid-August is the best time to transplant or divide your iris, as this is when the plant is not actively growing and yellow foliage can be inspected for the dreaded iris borer.
The process of dividing the iris is fairly simple. Start by digging up all the rhizomes and removing soil from the roots. Break up and separate the rhizomes, discarding any small roots and old rhizomes farthest from the leaf fan. Cut the leaves roughly in half to make the plant more manageable.
When replanting, prepare the soil with a generous scoop of compost or peat to help break up hard clay soils commonly found in Minnesota. Plant the rhizomes very shallowly, covering only the lower half of the root and leaving the top half exposed to the sun. Water thoroughly and wait until next May for a wonderful reward of iris flowers!.