Blooming in late spring (and some re-bloom in fall), these tough perennials flower in nearly every shade of the rainbow. Needing only a sunny spot, iris range from miniatures with flower stalks just six inches tall to towering types up to four feet tall. I've never seen an ugly iris.

Iris can persist for many, many years with little or no care. It's still possible today to come upon abandoned homesteads on Colorado's eastern plains where iris still grow, untended for generations. I have a few iris in my garden that were rescued from old homesteads. To my embarrassment, there are some clumps in my garden that have been nearly as neglected.

Ideally, clumps of iris should be lifted and divided periodically, usually every five to seven years. Without this rejuvenation, the plants deplete the soil they're in and decline in vigor and flowering. Iris may be divided at almost any time during the growing season. Usually gardeners do this in June or July, but rainy weather got in the way this summer. I'm finally getting around to some clumps of iris that have needed division for several years.

To divide iris, dig up a clump with a digging fork or spade. Tear it apart with your hands. Discard old, dry, pithy pieces of the rhizomes. Try to get down to single "fans" of leaves with two or three inches of form, healthy rhizome. Cut the foliage back by half so that the plants have less top growth to support as they re-establish their roots. This is the only time iris foliage should ever be cut back. Unless you're dividing, leave iris foliage alone or the plants can't collect enough solar energy to flower properly the next season.

Replant the fans in fresh soil, always in a sunny location. If you set some of them in the same place where they were growing, work in some compost to enrich the soil. Most iris rhizomes will settle in well during fall and may even bloom in spring. They'll get back to peak performance the next year.

Many nurseries are offering iris rhizomes right now. They're a very good investment, since iris are almost impossible to kill and persist for many decades. Expand your rainbow of iris colors this fall and you'll have lovely flowers for years to come.