Bearded irises: divide them now for healthy plants, full of flowers next year

First published by Rattan Direct on 29 July 2016.

Iris, the rainbow goddess

Iris was one of the Greek goddesses of the sea and sky, and was associated with the rainbow. Iris flowers span practically all the colours of the rainbow, like the human eye’s coloured iris (also named after her).

There are different kinds of iris but in late summer, we’re concerned with taking care of the easy-to-grow bearded iris.

Bearded? Yes. All iris flowers are made up of three upright ‘standards’ and three ‘falls’ which droop. Bearded irises have small, soft, fuzzy hairs (the ‘beard’) in the middle. Click on the image below to see this in more detail.

Blue bearded iris. Bearded irises
Blue bearded iris by Chicken Freak. Work released into the public domain.

Irises like the sunshine

They need at least six hours of sunlight a day (a full day is even better) and well-drained soil to keep the rhizomes dry. Rhizomes are the thick root-like structures which produce leaves, flower stems and roots.

As the plant matures, more rhizomes develop and produce more roots, leaves and flowers. Eventually, they become congested, the original rhizome withers and dies and the plant flowers less. Dividing the plant before this happens, and removing and replanting the new small rhizomes allows more plants to develop and more flowers are assured.

Iris rhizomes in allotments in Tourcoing (Nord), France. Bearded irises.
Iris rhizomes in allotments in Tourcoing (Nord), France. © Jamain and licensed for re-use under the lCreative Commons Attribution-Share Alike 3.0 Unported Licence.

By late summer, depending exactly where you are, the bearded iris flowers are over and it’s time to divide the plants, if they need it. Although the best time is straight after flowering, this can be delayed until early September. It’s best to divide the plants every three or four years.

How to divide bearded irises

Bearded irises in Doddington Place Garden, Doddington, Kent.
Bearded irises in Doddington Place Garden, Doddington, Kent. © pam fray and licensed for re-use under the Creative Commons Attribution-ShareAlike 2.0 Generic Licence.
  1. Lift the clumps carefully with a fork or spade.
  2. Divide the rhizomes by pulling them apart with your hands or use a sharp knife if necessary. Keep rhizomes that are about as thick as your thumb with healthy roots and one or two leaf fans. Discard large, old rhizomes with no leaf fans; any that feel lightweight or hollow; and soft, smelly or rotting plants.
  3. Shorten any long roots to 3cm or so (1.5 inches). Cut the leaves back to a length of between 10 and 15 cms (4 and 6 inches). This helps the plant to concentrate on growing new roots rather than trying to maintain its long leaves.
  4. Cut off the end of each rhizome so the healthy piece remaining is 8cm to 10cm long (3 to 4 inches).
  5. Replant the prepared rhizomes by fanning out the fine roots and setting each rhizome so that part of its top surface is just visible at the soil surface. Enrich the soil with some garden compost. Remember they like a sunny spot!
  6. Space the plants at a distance of 30 to 45 cms (12 to 18 inches). For the best display, plant the rhizomes so the fan of leaves all face the same direction, towards the sun. Water them well at planting and keep moist until they are established.

You’ll have healthy irises, full of flowers, if you follow our advice. And you’ll increase your stocks of plants too. Not bad at all.

Purple bearded iris. Bearded irises
Purple bearded iris. © KarinConway and licensed for re-use under the Creative Commons Attribution-Share Alike 3.0 Unported licence.

Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s