How to Divide Irises

The home we moved into last year was blessed with many large clumps of German Bearded Irises.  So many, in fact, that I think there may actually be too many.   At least, in comparison to what other types of plants there are here, which is pretty much nothing besides lots of foundation shrubs.

In these pictures from early May, you can see just how many iris clumps there are.  

While they are beautiful in bloom, they aren't all that exciting once the blooming season is over.  And so I think using them as a foundation border, all alone in front of the boxwoods, is not the design I want to have for the front yard.  So I've decided to dig them up, divide them, and re-plant them around the yard and garden in some other locations to mix them in a little more to other perennials.

You may want to divide your irises because they've become overgrown and started to die out in the center of the clump.  Or maybe yours have grass and other weeds growing amongst them and you want to get that out.  Or you'd like to propagate your clump to create more plants.   Whatever your reason, you'll find that it's fairly straightforward to divide these pretty plants.

The best time to divide German Bearded Irises is about 6-8 weeks after they have bloomed, but a couple of months before the first freeze in the fall.  This gives them time to invigorate themselves after blooming but also gives time to root themselves nicely before winter.

Here is the clump I'm digging up and dividing today.

This tutorial is going to follow be very similar to my tutorial on how to divide hostas, which I posted a few weeks ago. The principles are exactly the same.  First, pull any mulch away from the clump.

Using a spade or a garden fork, dig around the base of the clump to loosen it.  The Iris clump is typically only 4-6" deep, and you can generally see the rhizomes along the surface of the soil, so you know how big the diameter of the clump is before you begin digging.

 Dig on all sides, to loosen the clump from the soil evenly.

Pry up the clump, and gently pull the clump from the dirt.  You can use a tool or you can just pull gently with your hands.  (Save your back, lift with your knees!)

I like to lay the clump on a tarp, so that my sidewalks and grass don't have soil all over them.

Shake any excess dirt from the clump of rhizomes.  You can then see the individual rhizomes that make up the clump.  

Use your fingers to gently wiggle the individual fans of leaves and the rhizome to which the fan is attached.  You'll find that these clumps separate fairly easily.  

Some of them are already separate, and others of them snap off easily at the joints. 

Continue to separate the individual fans of leaves and their rhizomes.   You'll get down to a piece of the "mother" rhizome which has no roots of its own, and has no leaves of its own.

Throw away (not compost) any rhizomes that are mushy, smelly, or filled with worm holes.

Usually, I find the last little bit is made up of a mother rhizome and then some "antler" looking pieces that are just old flower stalks, with no fan of leaves.   You can leave these together like this, or you can snap the sides off and throw away the mother.

I think this one looks like a lobster.  :-)

After dividing, this is what this clump yielded.

Before replanting, I like to trim the fans down to about 8-10".  This gets rid of the drying and straggly ends and gives the plant a nice neat appearance.

Now the individual rhizomes are ready to plant again.   Just dig a shallow hole, lay the rhizome in the soil with roots down, and tuck in just deep enough to barely cover the rhizome.   If you plant them too deep, they will more likely rot from too much moisture. 

Keep the divisions evenly moist over the next few months, allowing the roots to take hold.  The fans may develop new leaves, or may not, but most of them will return next spring with a beautiful fan of leaves.   Sometimes new divisions don't flower in their first spring, so don't be surprised or disappointed.  But they should come back strong in the next season, and bring your garden lasting beauty!

For more in my "how to" gardening series, check out this post:

Thanks for stopping by!   

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