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How to divide iris rhizomes

Overview

Irises can become congested over time, which tends to inhibit flowering. This can be remedied by lifting and dividing their rhizomes to give them a little more space. Wait until flowering is over before dividing the iris clump, discarding any old, woody rhizomes and replanting only young, healthy plants into freshly-prepared soil.

How to do it

Irises being dug up

1Use a fork to dig up a congested clump of irises. Ease the plants from the soil, taking care not to spike the rhizomes.


Pulling apart iris rhizomes

2Pull the congested rhizomes apart by hand, or cut them with a knife. Choose healthy pieces with leaves and discard old, woody sections.


Trimming the leaves of an iris

3Newly-planted rhizomes are vulnerable to wind rock, so it's a good idea to reduce the leaves by half. Use a sharp knife to trim them.


Replanting irises

4Replant healthy rhizomes about 12cm apart with the leaves facing towards the sun. Make a shallow hole and half bury the rhizome, giving it a firm push to bed it in - they like to bake in the sun, so don't bury them too deep.


Adam's tip

It's a good idea to lift and divide clumps of irises every three years.



Discuss this project

Talkback: How to divide iris rhizomes
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molene 24/11/2011 at 15:28

I have some Iris's that I planted last year. They didn't flower then but I thought they would this year. Still no luck. What am I doing wrong?

luise_gregory 24/11/2011 at 15:28

Help! I am getting addicted to your website! Thank you so much for all your help and advice. I am a new gardener and you are my bible.
Question: Once Irises have stopped flowering. Can I cut off the flowering stem immediately? Do I leave it as with daffodils?
Thanks in advance for your reply.

Petew 21/08/2012 at 10:11

I Have planted iris's for the first time this year and they have come up a treat. Will I need to divide them this year or do I just leave them in the ground, also can i leave Gladioli corms in the ground or do I need to dig them up?

Berghill 21/08/2012 at 10:31

Lots of questions there. First of all first year Irises do not need splitting up. Next year maybe, if the rhizomes are overcorwded. Resons for non-flowering are many, but take your pick from, 1 too young, 2 underfed and 3 lack of sunlight on the roots last Summer.

1 Wait.

2. Feed with Maxicrop about now and Tomato type food in early Spring.

3. Move to a sunnier place. Or if the rhizomes are overshadowed or facing the wrong direction, change that. They should always be planted sp that the rhizomes are exposed to as much sun  as possible.

Next, o;d flowering stems. Cut the stem itself off back to where it emerged from the leaves. Clean up and remove and dead or dying leaves and you can if the tips are going brownl cut of the tops of the leaves, but to no more than half their length. The plant needs them for food production.

Gladiolus bulbs may be left in ,if you are on a well drained sandy soil and they were planted deeply enough for frost not to reach the corms, otherwise dig up and store over winter for replanting in Spring.

sotongeoff 21/08/2012 at 10:37

Berghill is right if these are flag irises-Petew- if they are dutch irises they can stay in-what sort did you plant do you know?

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