KC Gardens

It's time to divide iris

Photo by Malcolm Beck, Johnson County Extension Master Gardener

Tip of the Week

Early August is usually hot and dry. What a relief this year has been with the cooler than normal temperatures and much needed rainfall. The next few weeks might be one of the best times in recent years to get out into the garden and divide the overgrown clumps of the ever-popular iris.

Iris is one of the most easy to grow garden perennials. Although they provide years of pleasure with minimal care, periodic dividing is an important cultural practice for maintaining plant health.

Iris, as a general rule, should be divided about every three to five years. Without timely dividing, the plants simply outgrow their allotted space in the garden. The bloom quality of the clump also decreases when plants become overcrowded.

There is no simple way to approach a clump of overgrown iris but to just jump in and tackle the plant. Start by digging the entire clump. The good news is that the plants have a fairly shallow root system so deep digging is not needed. The recent rains will make it much easier to dig and prepare the soil.

Once out of the ground, start breaking the plants apart. Iris rhizomes are vigorous and almost indestructible. Knock the soil off the roots, then break and pull the rhizomes apart. You will end up with more divisions than anyone could possibly use, so discard small roots.

Iris rhizomes grow outward. The old rhizome furthest away from the fan of leaves can be discarded. All that is needed is the last knee or bump attached to the leaves. The rest is old, unproductive rhizome that is not needed for a healthy plant. Many prefer to cut the leaves back by one half to make the plant more manageable.

The hard part is now done; replanting the iris rhizomes is easy. Prepare the soil by spading and working in an ample supply of compost or peat moss to help break up the hard clay soils commonly found in our area. You are now ready for planting.

Iris rhizomes should be planted very shallow. Cover only the bottom half of the root and leave the top exposed to the sun. A nice size division or start is a grouping of about three prepared rhizomes. Point the leaves outward in a circle and cover lightly. Thoroughly water them in and the process is done.

Set back and wait till next May for a wonderful reward of iris blossoms. Enjoy one of this area’s easiest to grow perennials, as there is nothing finer than a graceful iris blossom. Mother Nature has graced us with almost perfect conditions so don’t miss your opportunity.

For more information on dividing iris view this short video produced by K-State Research and Extension. http://www.hfrr.ksu.edu/p.aspx?tabid=980&cat=FlowersandOrnamental_Grasses&itemid=93&cmd=view#93

(Photo by Malcolm Beck, Johnson County Extension Master Gardener)


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