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.
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.
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!).
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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