Monday, August 27, 2018

It's Time to Divide Your Bearded Iris by Donna Duffy

Photo by Carol King
Iris are one of the superstars of the spring garden. Keeping them blooming year after year requires some work. Do you have bearded iris that you want to move, or that aren't flowering as well as they did a few years ago? It’s probably time to dig and divide them.

Clumps of bearded irises should be divided and replanted before they become overcrowded. A single rhizome will branch many times over the years, developing into a crisscross clump, often choked with old leafless rhizomes. If it is not divided, the mass of leaves will exclude sun from the roots. This will lead to poor flowering or no flowering and often weakens the plants making them more susceptible to insects and diseases.

Lifting an iris clump with a spading fork
August is a good time to do your iris division, when they are no longer blooming. Lift each clump by gently prying it loose from the soil. A spading fork is better for this than a shovel because it is less likely to cut roots and rhizomes. Lift the clump and carefully wash the soil away from the roots.

Rhizomes that have been divided and trimmed
Start by pulling the rhizomes apart carefully, keeping the roots attached. Use a sharp, strong-bladed knife to trim younger rhizomes into sections that include healthy-looking roots and one or two strong leaf fans. Trim the leaves to about 4-6" in a fan shape.

Diseased or damaged rhizomes should be discarded
Discard old rhizomes from the center sections. Also discard segments of rhizomes that are soft or riddled with holes. 

Rhizome ready to replant

Planted! Note the top of the rhizome above the soil.
When planting the rhizome, spread the roots out in the soil and position the top third of the rhizome above the soil surface. Arrange foliage to face outward away from the center of a group. Evenly spread the roots and firm the soil around the rhizome to eliminate major air pockets. When planted correctly, the top of the rhizome will be visible above the soil. Water the rhizomes well.

A bonus: you'll have lots of rhizomes to plant, trade or share! If you've divided several colors of iris, write the color name on one of the leaves to help you when it comes to replanting. 

That’s it! You’ll be rewarded in the spring with a new bed of blooming iris. Repeat this process when iris clumps become overcrowded again. For more information, check out Plantalk Colorado, “When Should I Divide my Bearded Iris?”

Photo by Carol King