When and How to Divide Iris

Table of Contents

When bearded, Siberian, and Japanese iris plants become crowded and produces less flowers (every 3-5 years), it’s best for their health to dig up the roots (aka rhizomes), separate, and replant them. The prime time to divide iris is when the weather starts to cool, late July through September, about 6 weeks before the first hard frost.


1. Dig and loosen the soil around the perimeter of the iris clump. Then gently lift the rhizomes from the soil with a spade or garden fork.


2. Separate the rhizomes with your hands or by cutting with a sharp knife that is dipped in a 10% bleach solution after each cut. The bleach solution prevents the spread of disease from one plant to the next.

3. Remove the soil from the rhizomes and inspect them. Keep firm rhizomes that have both roots and leaves. Discard any older rhizomes without leaves and areas affected by soft rot or iris borer (look for tell-tale holes in the rhizome).

Pro-Tip: To prevent iris borer, remove and destroy the iris leaves after the first hard frost each year.

4. Trim the leaves down on an angle to about 6″.

5. Prepare the new location for the iris by digging a wide, 3-5″ deep hole. Set the rhizomes in the hole and cover the roots with soil. The rhizome should be slightly exposed above the soil, otherwise it may rot.

Pro-Tip: Iris plants look best when 5-7 rhizomes of each variety are grouped together. Locate the groups of each variety 18″ apart.


6. Water the newly transplanted iris, but do not mulch. Mulch retains too much moisture, which can cause the rhizomes to rot.


Share on facebook
Share on twitter
Share on linkedin
Share on pinterest
Share on whatsapp

Leave a Comment

Your email address will not be published. Required fields are marked *

More Posts You Will Love

Flowers for kids - young girl inspecting a big yellow sunflower bloom.

5 Easy Flowers for Kids to Grow

Kids love any opportunity to get their hands in the dirt! Discover our top tips for gardening with little ones and 5 easy flowers for kids.

troubleshoot your garden

Troubleshoot Your Garden

Welcome to our garden troubleshooting page! Here you’ll find everything you need to know about tackling garden problems. From wilting plants to insect invasions, we