How to Raise and Divide Irises

Updated on May 18, 2019
MariaMontgomery profile image

Maria is a Master Gardener, public health educator, grant-writer, artist, photographer, & proofreader. She lives in central Florida.

Dividing Irises Is Easy

The best time to divide irises is July through September. If you live in the South, however, they can be divided throughout the winter, but they may not bloom that spring.

I originally wrote this article when living in north central Alabama, but now live in central Florida. I moved some irises in January of 2014, and, to my surprise, one of them bloomed the following April. Usually when moved that late, they pout, and refuse to bloom that spring.

This article is about much more than how to divide irises. I will share what I have learned not only about how to divide irises, but also about raising irises, including their requirements, their tolerances, how to plant them (it's not the usual way), and even when to trash them.

I have been raising and dividing irises for many years, and have learned a lot about what works with them and what does not. They are easy to grow, drought-tolerant, and not overly choosy about their soil. Of course, the better the soil, the better they will grow, bloom, and show off for you.

I gained a love of bearded irises from my mother. Many people think of irises as old-fashioned flowers, but I find them to be exotic-looking and magnificent. They are one of many plants that gardeners often refer to as "pass-along plants" because they can be passed along from one gardener to another without harming the parent plant. That is how I received many of my irises, but first they must be divided.

Irises' Most Important Needs

Irises have few needs. But they really need those few things:

  1. Full sun — this means no less than six hours of sun per day.
  2. Well-drained soil.
  3. Rhizomes partly above the soil.
  4. No mulch on the rhizomes.

This bearded iris is called Feedback.
This bearded iris is called Feedback. | Source
Bearded iris rhizome.
Bearded iris rhizome. | Source

Rhizomes and Roots

In the above photo, you see the rhizome and roots of an iris. The large brown part is the rhizome. The long slender roots are the only part that should be underground.

Properly planted irises should look like little potatoes lying on the ground, as shown in the next photo. These are very drought-tolerant plants. So, if planted underneath the soil, or if mulched, the rhizomes will rot due to too much moisture.

Crowded irises.
Crowded irises. | Source

Irises Too Crowded

The above photo was taken in February or March after a very mild winter. The irises had just begun a new period of growth. They appear to have been planted correctly by the previous owner of this property, but they have grown far too crowded. It was past time for them to be divided.

Again, the best time to do this is from July through September. But it can be done at any time. I usually do it in late autumn or late winter because it is often too hot from July through September. However, if done in late winter or early spring, they probably will not bloom that year.

A temporary fix for crowded irises.
A temporary fix for crowded irises. | Source

A Temporary Fix for Over-Crowded Irises

If you do not have time to dig up the irises and separate them, there is another way. Be aware this is only a temporary fix.

Take a good look at your crowded irises. You will see some of the older, original rhizomes, from which newer plants have grown. Now that the newer plants are large enough, the older, "parent" plant can be removed. In this photo I have circled in yellow some older rhizomes to be removed. The pink circles are around two plants that I will dig up and place in another bed. The others I will leave in the same location until I decide what to do with them.

Here's how:

Take a sharp knife or, if stooping down is a problem for you, use a sharp shovel to sever the connection between the parent plant and the younger off-shoot plants. Then simply pick up the older rhizome and examine all sides of it.

If that older rhizome has the little rows of holes made by iris borers, (they're usually on the bottom) or if it is shriveled, soft, or has any wet rot, put it into the trash can. Do not put into your compost bin, because you could introduce the borers or any mold or disease from the rot into your compost.

On the other hand, if it has a tiny new sprout on the side, give a chance. Plant it and see what happens. If it has no roots, just lay it on bare soil, and press some soil up to it, but do not cover it — I have actually seen these plants take root when just lying on the ground. Then just give nature time to do her work.

This shows a partially rotted iris rhizome.
This shows a partially rotted iris rhizome. | Source

Never Mulch Irises

Iris rhizomes should never be mulched. This encourages moisture which will cause them to rot.

The above photo is an example of wet rot from too much moisture. This iris was probably planted in a good place, but mondo grass nearby has encroached on the irises in this bed. One of them has to go. It will be the mondo grass. Another problem causing wet conditions are the weeds and leaves that need to be removed. In autumn, be sure to remove fallen leaves from around your irises.

As you can see, the entire rhizome has not been damaged. I will cut or break off the tuber at the point where I have drawn the yellow line, throw away the rotted portion, then replant the remainder of the iris in a sunnier spot away from weeds and invasive plants such as mondo grass.

The rhizomes should look like little potatoes lying on the ground, with only the long slender roots beneath the soil. --Maria

Source

Never, ever put mulch

of any type on top of

your iris rhizomes.

— Maria

My First Hybridized Iris?

I didn't even try, but I may have a hybridized iris that needs a name.

I ordered a group of six irises from Springhill Nursery — one each of six colors: burgundy, purple, blue, white, yellow/purple, and orange.

The orange one was a free "bonus". This white/purple wasn't one of them. There was a white one that appeared to have died. Then this one (unfortunately, the photo has been removed by HubPages) came up in its place. Imagine my surprise when it bloomed.

I suppose it is possible that the growers sent me the wrong one, but I believe the purple one and the white one got together when I wasn't looking.Of the six plants, only 4 survived. The free one and one other one quickly shriveled up and rotted.

Maroon bearded iris.
Maroon bearded iris. | Source

Iris Day Is May 8

Did you know there is an Iris Day? It's May 8th every year, and is celebrated from late April through mid-June worldwide with festivals that include art shows, fun runs, beauty pageants, and much, much more.

This photo is of another iris whose name I don't know. It was on the property of our former home when we bought it. It didn't bloom the first year we were there, then we had some tree limbs removed and, with the additional sunlight, it began blooming each spring. Those irises demand their sunshine!

Digging in the Dirt

If you're like me, you're happier digging in the dirt, uh, I mean soil, than doing just about anything else. If you have garden stories, especially iris stories to share, please let me know. I would love to hear them.

Thank you for visiting my irises and me. I hope you enjoyed the article, and maybe learned a bit about this lovely, exotic-looking flower.

Questions & Answers

  • I have a 5-year-old bearded iris bed and great greens but they have never flowered. What can I do?

    By "great greens" do you mean great leaves? If they are not blooming, it could be that they are planted too deeply. It could also be they are not getting enough sun. Irises are sun-loving plants and need at least 6 hours of sun per day.

  • Which way do you orient the iris' rhizome so that the flower faces outward?

    Because iris flowers are the same all the way around, they don't face any particular direction. However, the rhizomes get longer and longer, seeming to creep across the soil as they grow, so I would suggest putting the end with the leaves facing an area that will give them space to grow across the planting bed. If you have plenty of space, it doesn't matter which way they face.

  • I’ve recently dug up my father’s very neglected iris garden. Many single irises have very long rhizomes. He said to just cut them in half. I see in your picture that you seem to have done the same. How do I know if there is a good cutting point?

    You can cut or break off the pups at the point where they are attached to the "mother plant". If you cut them, be sure to use a clean, sharp knife WITHOUT a serrated edge. Some of the older ones may appear shriveled or have rows of tiny holes in them. The shriveled ones have some rot. The little holes are from iris borers. Put either of these in the trash. Don't compost them. I have been known to cut off the shriveled parts, then plant the remaining part. If you do this, wash the knife very well before using it on additional rhizomes to avoid spreading disease to other plants.

  • My mother used to cut off the leaves about 8 inches up when she transplanted iris. I think that was to off-set the root shock. What do you, the writer of this article, recommend, should I cut my irises' leaves or leave them long?

    What she did is called fanning the iris. When cut like that, they look like an unfolded fan. It's done in the late spring or summer after they have bloomed. It makes transplanting easier, as removing the weight of the long sword-like leaves helps the plants remain stable until the roots have time to become re-established. I do recommend fanning them when transplanting, as well as every year after bloom season.

  • The iris that I bought are bulbs. What is the difference on planting them?

    I think you must have bought Dutch iris or Japanese iris. They can be planted rather than laid on the ground as are the rhizomes of bearded iris. The bulbs are winter hardy in zones 5 - 9. They should be planted 6 - 8 inches deep, and look best if planted in groups. If you want them to multiply and come back year after year, plant them in well-drained soil that is warm and mostly dry in summer.

© 2012 MariaMontgomery

Do You Raise Irises? Do You Need to Divide Your Irises?

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    • MariaMontgomery profile imageAUTHOR

      MariaMontgomery 

      3 days ago from Central Florida, USA

      Hi Diane, Sorry to take a week to reply, but we just moved, too, and I am still trying to find things. You should be able to dig them up in January. Planting them that close to spring, they may not bloom until the following year, but it's worth a try. I did move some to central Florida, but they lasted only a couple of years, then died. I was in Zone 9a at the time. I'm now in south Alabama in Zone 8b, the same zone as Tallahassee. All my research shows they should do well in this zone. Japanese iris and Dutch irises also do well in both Zones 9b and 9a. I hope this info helps you, and good luck with your move.

    • profile image

      Diane White 

      11 days ago

      Hi, I am moving from ky to tallahassee, fl in the very beginning of Jan. Can I dig up some of the iris and plant in fl in Jqnuary? I have bearded iris and I'm afraid if I dig them up now which is Nov. 12 they might not make it to January. Any suggestions when and how to dig up for fl?

    • MariaMontgomery profile imageAUTHOR

      MariaMontgomery 

      2 months ago from Central Florida, USA

      Hi Virginia, they are among my favorites, too. It's the perfect time to move them. I'm glad you have a sunny spot to put them. You should get lots of flowers next spring. Be sure to let me know how they do.

    • Virginia Allain profile image

      Virginia Allain 

      2 months ago from Central Florida

      Iris are among my favorite flowers, as my mom always had lovely ones. I'm going to move my ones in New Hampshire over to a new (more sunny) bed. It's the end of August, but I see in your article that the timing is OK. I'll make sure to leave part of the rhizome above ground and not to mulch them.

      Hopefully, next spring I'll get some flowers which I've been missing the last 2 seasons. Lots of big trees in my yard.

    • MariaMontgomery profile imageAUTHOR

      MariaMontgomery 

      4 months ago from Central Florida, USA

      Hi, Janice. If you clean all the soil off of them, then store them in a cool, dry place, they should be fine for a while. If it were me, I would lay them on top of the ground, and put a little soil over the long slender roots until I could see my kids. At that time you can simply lift them up and put them in a bag for the kids. Thanks for reading my article, and for commenting.

    • profile image

      Janice Kinder 

      5 months ago

      I divided my bearded irises the last week of June. Was it too early? (I live in Connecticut.) Also, I replanted, but I have a ton of good rhizomes left. How long can I keep them, because I want to give some to my kids, but I might not see them for a week or two. How long will they last?

    • MariaMontgomery profile imageAUTHOR

      MariaMontgomery 

      5 months ago from Central Florida, USA

      It could be one or more of several things. If they aren't getting enough sun, they will stop blooming. Full sun is 6 or more hours of sun per day.

      Often, soil will gradually build up around and even over the rhizomes. This can be caused by heavy rains washing the soil onto them, or just pushing into the soil as they grow. You can "lift" them if they have gradually gotten too deep.

      Look for horizontal rows of tiny holes on the rhizomes caused by iris borers. If you find that, spray with an insecticide. I use insecticidal soap or Neem oil. The soaps will need too be reapplied after rain or irrigation. The oils will melt and slide off in intense heat. If borer damage is really bad, you can cut off the compromised rhizomes and put them in the trash, not your compost pile or bin.

      Irises need some extended cold weather to thrive. I tried grow them here in central Florida, and they did fine for the first 3 or 4 years, but died by the 5th year. I finally gave up. I hope this helps. Good luck with them.

    • profile image

      Barbara Brewer Tobitt 

      5 months ago

      My irises look like they are dying brown leaves an very few blooms this year they were beautiful last year what should i do for them?

    • MariaMontgomery profile imageAUTHOR

      MariaMontgomery 

      5 years ago from Central Florida, USA

      @Richard1988: Thank you, Richard. I do enjoy digging in the dirt, and working with plants. Thanks, too, for the squidlike and for your comment.

    • Richard1988 profile image

      Richard 

      5 years ago from Hampshire - England

      Those garden tool sets look great! You're clearlyba bit if a green thumb!

    • MariaMontgomery profile imageAUTHOR

      MariaMontgomery 

      5 years ago from Central Florida, USA

      @favored: I bet it was breathtaking. Wish I could have seen it. Thanks so much for the squidlike and for such a nice comment.

    • favored profile image

      Fay Favored 

      5 years ago from USA

      I have used the same company with good results. I used to have a flower get with just Iris in it called "Iris Island." It had hundreds of plants and looked so lovely in full bloom. Thanks for the tips here, especially for composting.

    • MariaMontgomery profile imageAUTHOR

      MariaMontgomery 

      5 years ago from Central Florida, USA

      @GrammieOlivia: Aren't they just gorgeous? I have only a very few that I brought with me when we moved, because I didn't think they would grow here. Now I need to get more. Thank you for the squidlike and for your lovely comment. Thank you, too, for sharing it with weekend gardeners on FB. I need to check out that group. Do I need to request membership?

    • profile image

      GrammieOlivia 

      5 years ago

      Love Irises, they just bloom so quickly and then they are gone.... :( But the beauty they give while in bloom is to die for. Lovely lens and sharing it right now with our weekend gardeners on FB!

    • MariaMontgomery profile imageAUTHOR

      MariaMontgomery 

      5 years ago from Central Florida, USA

      @paulahite: Thank you so much. Thanks for the squidlike, too.

    • paulahite profile image

      Paula Hite 

      5 years ago from Virginia

      Lovely! and on Facebook today!

    • MariaMontgomery profile imageAUTHOR

      MariaMontgomery 

      5 years ago from Central Florida, USA

      @Zeross4: Thank you, Daisy for the thumbs up on this lens, and for your comment.

    • Zeross4 profile image

      Renee Dixon 

      5 years ago from Kentucky

      I love irises, they are so beautiful. I will have to remember this information in case I'm ever able to raise my own :)

    • profile image

      StrongMay 

      5 years ago

      We have purple irises. We pretty much ignore them, and they have bloomed beautifully like clockwork every year, without exception. We even transplanted them a couple times as we moved. They certainly multiply nicely! We give them lots of space.

    • MariaMontgomery profile imageAUTHOR

      MariaMontgomery 

      5 years ago from Central Florida, USA

      @takkhisa: I love them, too. Thank you so much for the squidlike and for your comment.

    • takkhisa profile image

      Takkhis 

      5 years ago

      I love Iris and it can be found where I live, especially in the public gardens.

    • MariaMontgomery profile imageAUTHOR

      MariaMontgomery 

      6 years ago from Central Florida, USA

      @anonymous: Thank you.

    • profile image

      anonymous 

      6 years ago

      pretty. you have green thumb

    • MariaMontgomery profile imageAUTHOR

      MariaMontgomery 

      6 years ago from Central Florida, USA

      @Frednun1965: Thank you! I do love my irises...

    • Frednun1965 profile image

      Fred Alb 

      6 years ago from Uruguay

      Wow!

      Very nice work!

    • MariaMontgomery profile imageAUTHOR

      MariaMontgomery 

      6 years ago from Central Florida, USA

      @tracy-arizmendi: Thank you, Tracy1973. They're my favorite flower. Happy New Year to you!

    • tracy-arizmendi profile image

      Tracy Arizmendi 

      6 years ago from Northern Virginia

      Beautiful photos. I love irises.

    • MariaMontgomery profile imageAUTHOR

      MariaMontgomery 

      7 years ago from Central Florida, USA

      @LiteraryMind: I'm so glad you found it helpful. Enjoy those iris. I still need to "fan" mine. Thanks for the squidlike on this, one of my favorite lenses.

    • LiteraryMind profile image

      Ellen Gregory 

      7 years ago from Connecticut, USA

      This came just in the nick of time. I have a clump of iris I need to move and until now, I had no clue what I was doing or how to do it.

    • MariaMontgomery profile imageAUTHOR

      MariaMontgomery 

      7 years ago from Central Florida, USA

      @Sylvestermouse: You're welcome. Thank you for the squidlike and comment. They are appreciated. I hope your irises do well.

    • Sylvestermouse profile image

      Cynthia Sylvestermouse 

      7 years ago from United States

      Iris are beautiful flowers! Thanks for the directions to properly separate/split tubers.

    • Mickie Gee profile image

      Mickie Gee 

      7 years ago

      Most excellent page about how to divide iris. Love the instructions and images. If you find that you are missing some tubers one day, don't ask me about them; I will deny everything--even knowing where you live!

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