Irises are funny things. They are a hardy rhizome, or at least I’ve always had hardy ones that seem to grow no matter what. I mean, as long as they have a little sunshine and something to sink their roots into they’ve grown for me, whether or not they were even planted in the ground or simply sitting on top of the soil. However, for best results, I have learned a few things over the years.
First is that you should divide them every few years in mid to late summer so they have time to redevelop the root system for the following year. You will know when, because undivided irises will have diminished blooms due to overcrowding. Fear not, as dividing means you’ll have plenty to give away to friends and family. Think of them like the Amish Friendship Bread of the flower world. After dividing, plant them every eighteen inches with the top of the rhizome as close to the soil line or slightly above and the roots below. Water well.
Secondly, you should trim the blades before autumn to about six inches from the top of the rhizome. Like with most bulbs and rhizomes, waiting until they have been able to absorb as much moisture and nutrients as possible before cutting them will ensure a fabulous display for next year. Irises actually have a much longer blade life than most bulbs, and tucked into and between other blooms they provide a nice foliage backdrop for annuals such as alyssum, lobelia and petunias, but also work well in a perennial garden. Think of them as fillers once the blooms have faded by simply cutting off the stem, which, in some varieties, will also stimulate reblooming.
Lastly, it is important to get rid of any rotting or diseased looking rhizomes. Typically this is caused by planting in clay or nearly impenetrable soil in which water sits on the ground for too long and causes the iris to rot. While it is possible to grow irises in clay soil, it is best if it is broken up and some form of soil amendment is added to keep it from forming a solid mass again. Old leaves, compost, even potting soil will help.
And so today after breakfast, I plan on taking those irises we gathered from the old house, which was only a small fraction as there are hundreds of them, and finding new homes for them both here in the yard and giving a few away to friends and family. I wish I would’ve taken more, but at the same time with as fast as they grow and so few places to put them here, I’ll have a replenished stock in no time.