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How to Divide Bearded Irises in 6 Easy Steps

sky-blue Bearded Irises, ready to be divided
Image Credit:
freya-photographer/Shutterstock
Written By: Robin Sweetser Gardener
Almanac Guide to Herbs

The blooming of the bearded irises is something I eagerly await each spring. This year, I made a mental note to divide and move the irises in late summer or early fall, after blooming. Here’s how to divide irises—with step-by-step pictures.

Why You Should Divide Irises

Even though my irises were planted years ago and are terribly overgrown, the blossoms were still gorgeous this spring. However, dividing irises every 3 to 5 years is a normal part of iris care. This allows the clump to rejuvenate and bloom better (not to mention a way to multiply your irises to fill in the gaps). 

Also, it’s helpful to avoid the iris borer, a very destructive pest typically attracted to older, overcrowded gardens. 

All of my irises came from the gardens of family and friends, so they are precious to me, and I don’t want to lose them due to neglect.

When Should You Divide Irises

It’s important to divide and replant at the right time of year. In many regions, July and August are the best months to dig, divide, and transplant bearded irises. You can probably get away with dividing through mid-September, too. Do NOT divide in the spring. You must do this job post-flowering during the summer.

This is hot, heavy work involving a lot of digging, so I waited until the weather cooled down a tad before starting. My goal was to rework the iris beds, add some compost, eliminate the invading sedums and tree roots, and divide and replant the crowded rhizomes.

Best time: Divide bearded irises about 6–8 weeks after flowering, typically July through September depending on your climate.

irises and pachysandra.
The irises are getting crowded and encroached upon by pachysandra. The bed they are in is narrow and next to large rocks leaving the irises nowhere to go.
bare iris rhizomes
Even though bare rhizomes can survive out of the ground for 1 to 2 weeks without any damage, it is best to replant them right away.

How to Divide Bearded Irises

Step 1. Dig Up the Rhizomes

First, dig the rhizomes up. Try to dig carefully around the plants so as not to do any unnecessary damage to the rhizomes.

dug-up iris
Step 2. Inspect for Disease and Iris Borers

Check them for disease or insect damage We found some borer damage and mushy rhizomes that were discarded.

iris rhizomesiris rhizomes

Step 3. Remove Old Rhizomes

Snap or cut off the old part of the rhizome, since it will not flower again.

iris roots and rhizomes

The roots are quite long and will help anchor the newly planted rhizome in place.

Step 4. Prepare the Soil

Amend the soil with compost and dig a shallow hole or trench. Make a mound of soil in the middle to place the rhizome on, spread the roots out over the mound, and cover them with soil.

planted irises

Step 5. Replant the Rhizomes

Leave the top of the rhizome exposed.

planting an iris

Next season’s plant emerges from the fan end of the rhizome so when replanting, face it in the direction you want plant growth to travel. Space the pieces 12 to 24 inches apart for tall types, closer for dwarf ones.

irises that have been planted

I planted mine closer, for a more immediate display, knowing that I will have to divide them again sooner.

It is easier to plant if you cut the tops back to about 6 inches tall.

the tops cut off of transplanted irises

Step 6. Water and Care for Newly Planted Irises

Water well to settle the soil around the roots and continue to water deeply once a week until new growth appears. Once established, bearded irises are drought-tolerant and won’t need additional watering. Fertilize early in spring and again right after blossoming with compost or a low-nitrogen fertilizer.

It was sweaty work, even on a cool day, but so rewarding to see it done. We had enough leftover rhizomes to plant another bed on the other side of the stone wall. Next spring we should have twice the blossoms!

Frequently Asked Questions

How often should irises be divided?

Most bearded irises benefit from dividing every three to five years to prevent overcrowding and maintain vigorous flowering.

Should iris rhizomes be buried?

No. The top of the rhizome should remain slightly exposed above the soil to reduce the risk of rot.

Can you divide irises in spring?

It’s best not to. Dividing irises in spring can reduce flowering because the plants are actively growing. Wait until after blooming in summer.

Why aren’t my irises blooming?

Common reasons include overcrowded rhizomes, too much shade, planting too deeply, excess nitrogen fertilizer, or a lack of dividing every few years.

Learn more about growing irises in the Almanac’s Iris Growing Guide.

Transplanting
About The Author
Robin Sweetser

Robin Sweetser

Gardener

Robin Sweetser is a longtime gardening writer, editor, and speaker. She and her partner, Tom, have a small greenhouse business, selling plants and cutting flowers and vegetables from their home and lo...
Read More from Robin Sweetser

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Comments

<span>Joyce</span> Sun, 09/05/2021 - 12:42
The next to last picture and the last picture show different soil levels. Should the tuber be covered with soil, or not? What about wood chip mulch?
<span>Florence Welborn</span> Fri, 06/21/2024 - 10:37
Love the iris. Thank you for the help.
<a title="View user profile." href="/author/robin-sweetser">Robin Sweetser</a> Mon, 09/06/2021 - 09:26

The next to last picture is to show how the tubers were placed. In the last picture some of them have been covered with a thin layer of soil, which is okay. Much of it gets washed away when watering or during a rain storm. The trick is not to deeply bury the rhizomes. When you mulch, try not to cover the rhizome. Just put it on the bare soil around the plants.

 <span>Anita Anderson</span> Mon, 08/23/2021 - 13:31
Thank you! I'm leaving the state and going South soon! plan to bring some of them down there in my garden there ! I did not know about cutting the tops off. THIS WAS VERY INFORMATIVE and HELPFUL to me ! Thank you for having this for us faithful gardeners out there ! Does anyone know why my bearded irisses did not bloom this year ? A lady in my church said they only bloom every 4 years ? I never heard of that. They did bloom last year ! All of them! I do feed them in March and June. as all my plants.
<span>Frances Gale</span> Fri, 09/29/2023 - 03:42
my irises bloom every year
<span>Tobey</span> Sun, 08/22/2021 - 09:57
I have known for a long time that iris should be divided in August, but never found any detailed instructions for how to go about it. Robin to the rescue! Thank you so much for the invaluable step by step direction with great photos!
<span>Mike</span> Fri, 09/04/2020 - 22:40
I have Siberian irises. Noticed someone asked about dividing those. It's similar, but I didn't get small, tidy, individual stalks to replant. After 5 years, they slowed blooming and I could see the center was dead, an outer ring still green = time to divide. Ugh. Big chore. I only had 3 of them. Each had to weigh 40 pounds by the time I got them out, loaded with soil in the roots, etc. Tried different methods to separate clumps and get rid of the dead areas and after failing and struggling many times, I settled on a handsaw! Should have thought of that first. It worked. Put them all on tarps - lots of dirt, easier to clean up. Replanted the vigorous growth, dumped the dry, had lots for the back yard and front. The first spring, however, this year, only two flowers showed up after all that stress. The foliage is looking good, though. I'm feeling confident that they'll come back next year with a nice bloom. But seriously, be very cautious dividing irises or hostas or any well established perennial. I hurt my shoulder badly. Pinched a nerve. Weeks to feel better. Of course, that's just a cautionary message from a middle age dude! I should have grabbed that saw first thing. At least it's something that only has to be done every 3 to 5 years!
<span>El</span> Fri, 09/04/2020 - 07:29
Thanks for the (very timely!) article on dividing and replanting bearded irises. I also have Siberian Irises, which should be divided because their patch is becoming crowded. Do I follow the same steps as for the bearded irises? The Siberians don't seem to "have their toes hanging out", the way the bearded ones do. Or should they? Thanks for your assistance!
<span>Ashley</span> Wed, 07/08/2020 - 09:01
Wonderful guide to dividing and caring for Bearded Irises, thank you for sharing! I am moving in the near future and want to take my Irises with me as they were also gifts, I wasn't sure how to go about it, but now I'm a lot more confident about tackling the project. Thank you!
<span>Carolyn T Fields</span> Sun, 09/01/2019 - 13:14
I planted irises about a year and a half ago, in zone 7a -- Montgomery, AL. They have not bloomed. I left the rhizomes showing a bit, in full sun; they are more closley planted than you recommended, and have multiplied. Just no blooms. Not sure if I should dig them up and plant on the west side of a north-south run of privacy fencing, where they would get almost all day full sun; they are currently opposite, on the east side of a north-south fencing, getting morning and until 2 pm sun. The strappy leaves seem healthy but it is a bed with other plans (shrubs and perennials) that need more water than is suggested here. Do they like it drier?