how to divide irises

How to divide irises

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The front garden in my first home featured huge, gorgeous bearded irises that framed both sides of the front door. The massive blooms were a deep purple hue, and you had to be careful not to brush them with your clothes as you went into the house. Sadly, that house and garden were torn down after we sold, but luckily, I had divided some irises and gifted them to my mom, who in turn gifted some to me once I moved into my current house. These beauties live on in my front garden. Now it’s time to divide again, so here are a few tips that explain how to divide irises.

Even though they produce a rather short-lived bloom, irises remain one of my favourite ornamental plants. And I’ve found them to be pretty hardy and drought tolerant. Years ago, when I divided my first bunch, I was in the middle of overhauling my whole front yard, so they sat in buckets of water, as recommended by my neighbour (some for a few weeks!), before I was able to replant them. Once nestled safely in their new garden home, the irises all survived the winter. One thing to note, however, is that irises may not bloom the year after they’re divided or transplanted, but be patient. They should eventually rebloom for you.

deep purple iris

My first iris via my first home’s garden, via my mom’s last garden, now in my current garden!

How to divide irises

Mid- to late-summer is a good time to divide bearded irises. You want to make sure that the roots have ample time to grow before winter. You can usually tell that your irises are ready to be divided when a clump looks overgrown, with rhizomes starting to grow into each other and popping up from the soil. They also may not produce as many blooms. Every three to five years is a good rule of thumb for dividing irises.

knowing when to divide irises

A mess of rhizomes is a clear indication it’s time to divide your irises, especially when they’re pushing each other out of the soil!

I’ve read articles recommending using a garden fork, but I use a rounded spade as that’s what I have in my tool shed, and I find I don’t risk splitting any errant rhizomes. What I’ll do is I’ll put the tip of my shovel in the soil a few inches from the clump, dig down, and lift, going all the way around in a circle doing this until I’ve managed to loosen a clump. I’ll pull out the clump and then by hand, I’ll carefully separate the rhizomes, tossing any dead leaves or rhizomes without leaves attached into my compost-destined garden trug as I go.

This is a good time to amend the soil, though you want to make sure you don’t add too much nitrogen, as it can cause soft growth and make the plant susceptible to disease.

For the rhizomes you decide to keep, cut the leaf fans back so they’re about four to six inches long. This helps the plant focus on growing roots before winter.

Replanting your divided irises

Irises like sunny spots in the garden that get about six or more hours of sunlight a day. They’re also pretty drought tolerant, so a nice option for sunny areas of the garden. Irises also like well-drained soil. Though they enjoy a slightly acidic soil, they thrive in most conditions.

To plant, dig a shallow hole and create a mound in the middle where the rhizome will sit. Place the rhizome on the mound with the roots in your hole. Cover the roots and then place a thin layer of soil over the rhizome. You want the rhizome itself to be just below the surface, lightly covered in soil. Push any errant roots under the soil with your finger (they tend to pop up sometimes!).

replanting divided irises

I use scissors to cut the fan, before replanting my irises.

Plant rhizomes about 12 to 24 inches apart. If you plant them closer together, you just may find yourself dividing them sooner, but if you’re okay with that, then plant them as you will!

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49 Responses to How to divide irises

  1. Beverly Asleson says:

    Thank for the picture I’m visual 👍

  2. Margaret says:

    What a timely post! I have a huge clump of irises that I haven’t touched in the 9 years we’ve been here so it’s perhaps time that I did something about them 😉 Thanks for the tutorial, Tara!

  3. Barb says:

    Should you do this with Siberian irises?

  4. Cindy says:

    If you leave the top of the rhizomes out of the soil it helps them bloom. I like to leave some of it exposed so the sun can tell it to bloom. Just my own experience. I love the Iris too! Thanks for your work!

  5. Cory says:

    I have bearded iris that are in a crowded.container and haven’t bloomed for about 3 yrs. Does it matter what time of year i dig up and divide them since there’s no blooms. Would like to Thin out now.(mid April ).
    Thanks so much.

    • Tara Nolan says:

      Hi Cory, Mid- to late-summer is best. But if you’re eager to thin sooner, just be sure to wait until the soil warms up. They likely won’t bloom for you this year if you transplant, but you may have luck in the next year or two. 🙂

  6. Emily Bennett says:

    Thank you for posting…this was on my to-do list but thought I had to wait until fall. Now I know!!

  7. Cheryl Boulay says:

    Do you have a separate bed for your Iris? I have them in with my other flowers and wonder if they are not blooming because the rhizomes are not getting enough sun. Thank you.

    • Tara Nolan says:

      I have some in a separate bed and some in a new bed. The ones in the new bed didn’t bloom this year because I divided them last year. Sometimes it takes a year or two for them to rebloom. The garden where I took the divisions was business as usual this spring!

  8. Leems says:

    Will the rhizomes grow if still have roots but have been hacked apart?

  9. Paula says:

    We are in the process of reorganizing our perennial garden, so I am digging up all the iris and lily bulbs, and will replant them once we refill the garden with new soil. How should I store the bulbs over the next week or two until I can replant them? Thank you

    • Tara Nolan says:

      Hi Paula, the first time I divided my irises and didn’t replant them right away, I put them in buckets of water, just around the roots (as per my neighbor’s suggestion). They were fine. Now if I were to do it, I’d probably plant them in soil in buckets until they’re ready to go back in the garden.

    • GLENN TROESTER says:

      Schreiner’s, one of the largest iris growers in the world, warns that iris must not get too much water because it causes rot. So, NEVER put rhizomes in water for more than a few minutes.

    • Michelle says:

      I left them in a box in my kitchen for more than a season and they still bloomed once replanted, not the first year though.

  10. Kim says:

    I have a few large areas of irises that I need to divide. Rather than dig up the entire huge clumps, is there a recommended amount I could leave behind while I replant the newly divided rhizomes?
    Thank you!

    • Tara Nolan says:

      Hi Kim, it may be hard to not dig up the entire clump as they can become entangled. You may want to tackle one big clump at a time, gently disentangle them all and replant some in the original site, and then take the rest to the new area. How many you leave is a matter of aesthetics. 🙂

  11. B.Scott says:

    Thanks for the very much needed tips as I was given irises probably 8 years ago and never devised them but they just get bigger and bigger every year. That said a friend of mine requested a plant after they are done so this article is much appreciated.

  12. Lori says:

    I’m moving from Texas to Florida and want to take some of my bearded irises with me. I won’t be able to plant them (once dig up) for two weeks. How would you suggest I store them during that time? In water, soil, ziplock bag?

    • Tara Nolan says:

      Hi Lori, Irises don’t like to be too wet or too dry. I would put them in a paper bag with some fresh soil to transport.

    • Shawn says:

      The last time I moved, I took all my iris with me. I dug them up, left them all together, and packed them into paper bags with some soil. When I got to my new place, I separated them and trimmed them before replanting. They were in the bags for about 2 weeks and they did amazing. I think I may have spritzed them with water 1 time but that was all.

  13. Marilyn says:

    I transplanted last fall hardly any bloomed this year?

  14. Lori Skipper says:

    This is a great tutorial, to be never divided irises before and I have a huge patch of irises but I only get three or four blooms. I knew it needed to be divided.

    • Lori Skipper says:

      Sorry for the spelling errors, I haven’t ever divided irises before, I have a huge clump and hardly any blooms. Your tutorial will allow me to replant these for future beauty in my garden

  15. LuAnn says:

    Hi Tara, I’ve had a bed of irises for about 15 years and they have only been divided once. Up until the past year or two they were doing pretty good. Unfortunately that was the time frame I was diagnosed with breast cancer and was unable to take care of my yard. Now they don’t bloom and I have noticed that they are rotting quite a bit. Do I need to move all of good ones to a new flower bed? I’m afraid that if I leave any in the original flower bed they won’t survive.

  16. Cassie says:

    Do you water them after they die back? Thx

    • Tara Nolan says:

      I’ll give perennial gardens a good soaking here and there if we haven’t had rain. But generally I find irises to be pretty drought tolerant.

  17. MARY CHARBONNET says:

    Okay, I’ve dug them up and shaken off the dirt. How do I divide the risomes, with a knife or just break them? Most of them are grown into each other. Thanx.

  18. Nina says:

    My MIL tells me I should have the rhizome top uncovered so the sun can encourage flowering. Have you found this to be the case? I’ve about to transplant mine from the temp bed back to their usual spot after having the garden redone

    • Tara Nolan says:

      Hi Nina, I’ll lightly cover the rhizomes with soil, but I find they end up a little bit uncovered anyhow. It’s likely a transplanted iris won’t bloom that first year after you re-planted it.

  19. BARBARA ZIERLE says:

    I have trouble with wildlife eating bulbs (various kinds) that I plant. I have some established bearded, re-blooming Irises that have not been bothered. I purchased some (10″ X 10″ X 7 or 8 ” deep) plastic bulb cages. It seems like I might need one separate basket for each Iris bulb. I don’t see how the thick rhizomes can grow through the plastic top. Any ideas?

  20. Peter says:

    Is oct too late here in ny area? Been 55-70 degrees
    Ty

  21. Sheila Trott says:

    I have irises in container pots,should I take them in the garage or just leave them outside?

    • Tara Nolan says:

      Hi Sheila,
      I would either nestle the pot in a garden and put leaves or mulch around to protect, or put it in the garage. I haven’t grown irises in pots, so I’m not sure how vulnerable they are to the freeze-thaw cycles of winter. Also, if the pots are terra cotta or clay you’ll want to protect those, too.

  22. Carolyn Ramos says:

    It is now early November. What problems would i have dividing the rhizomes now.

    • Tara Nolan says:

      Hi Carolyn, I like to give divided irises time for the roots to become established before winter. Also, it’s possible they could heave as the ground freezes and thaws throughout the winter.

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