How To Plant Iris Rhizomes In Your Garden

This past weekend I transplanted a few clumps of "black" bearded irises in my garden. The first time I planted iris rhizomes I thought they were planted similar to canna rhizomes and planted them too deep in the soil. A couple of clumps of iris rhizomes never bloomed and some bloomed only sporadically over the next few years. While reading a garden book one day I learned that the reason for the poor flower production was probably due to planting the rhizomes too deep.

'black' iris growing in my urban garden. How to Plant Iris Rhizomes in Your Garden.

bearded iris divisions ready for re-planting in the garden.

When I dug up and divided these iris rhizomes I found that I had a problem with the iris borer that was bigger than I had estimated this past summer while doing some inspections in the garden. After tossing away the rhizomes that were infected by this pest I cut down the leaves to make sure any iris borer larvae that remained had less places to overwinter.

While replanting these I made sure the exposed rhizomes were facing south to receive as much sun as possible. I placed them on small mounds above the soil level as recommended, and spread the roots out to give them space to grow.

A side view to illustrate the soil mounds mentioned above. See how they raise the iris rhizomes higher than the ground? Make the mounds a good height because the soil will settle when you water or it rains and if they sink below a couple of inches they may rot. If you're planting them in a low spot in your garden where water is prone to pool, make your mounds even higher to accommodate any settling.

Once the rhizomes were positioned properly, I filled the area with garden soil making sure to cover the roots and leave just the rhizome divisions exposed.

The best time to plant bearded irises in your garden is July-September, because this gives them time to become established before winter and bloom the following spring. When I first planted the single rhizome that all of these, there's more than what's pictured here, came from I planted it in the fall because that's when I bought it and it bloomed the following spring. Irises are such low-maintenance perennials, perfect for beginner gardeners, that I recommend everyone should grow some.

Larvae of the iris borer that I found this summer in my garden. If you notice your iris rhizomes are rotting you may have some of these pests attacking your iris clumps.