by Jo Lucas, Guernsey County Master Gardener
After the rush of spring planting and lawn care, it seems like we have fewer things to do in our gardens as far as planting and making new beds. However, the weeks of summer can also be quite busy in the garden.
One chore that we can never seem to do enough of is “deadheading” or removing the spent blooms from plants to keep the plants blooming for a longer period of time and also to let the beauty of the new blooms to show without the distraction of faded, often mushy old blooms. Some plants benefit from being cut back almost to the ground so a flush of new growth can renew the plant while others such as lilacs, forsythia, and many other shrubs are already making the buds for the next year’s flowers. Those plants should be pruned immediately after the flowers fade so you don’t compromise the next year’s bloom.
Some perennials may become overcrowded, not bloom as well, and need to be divided every 4 or 5 years. One perennial that ends to become overcrowded is the bearded iris. The best time to divide these plants is right after they quit blooming, although with proper care they can be moved at any time.
Bearded iris, plant family Iridaceae, come in a wide range of colors, enjoy full sun, and usually bloom in June. They are a beautiful flower, very showy and bright, easy to grow, but a high maintenance plant. They need regular removal of old flowers – daily in many cases as each individual bloom usually lasts only one day. After all flowering is finished, the flower stalk should be cut down to the foliage. Leaves often become marred by different foliar diseases after flowering. These leaves should either be cut or pulled off to help control the diseases and to make the plant look more tidy through the rest of the summer. Often it is best to shear the foliage at 4-6 inches above the ground. Other problems iris are sometimes bothered by are borers and root rot. Dark streaking in the leaves are evidence of borers; prune off the leaves and dig out affected rhizomes (roots) and discard them. Do not put the infected plant material in your compost pile. Soft rot of the rhizome often comes from being overcrowded, planted in poorly drained soil or planted too deep.
Most varieties of iris are very vigorous growers and need to be divided every 3 to 4 years, as the best bloom usually occurs the second through fourth year. Iris will grow in almost any garden soil as long as it is well drained, as iris will not tolerate “wet feet.” They prefer a full day of sun, but will grow and bloom well with at least half a day of sunlight. When dividing iris, lift the clumps of rhizomes from the soil, separate them so each fan has its own rhizome. It is best to use a knife or scissors to cut them apart rather than breaking them apart, and then leave the cut rhizomes exposed to sunlight for a few hours before replanting or you can lightly dust the rhizomes with sulphur. When replanting, the soil should be worked up well and a small mound made to set the rhizome on, with the roots spread out. Cover with soil firmly packed down with your hands. The soil should not quite cover the top of the rhizome exposing it to sunlight. The leaves should be cut off about 6 inches above the rhizome in a fan shape so that it doesn’t fall over and disturb the rhizome from the weight of the leaves. The most attractive way to plant iris is to put the rhizomes in a triangle with the “toes” in and the “heels” (the end the leaves grow from) out, so that as they spread they will spread outward away from the toes.
Sometimes the rhizome develops a very long toe which should be shortened when replanting. A no-nitrogen fertilizer or super phosphate fertilizer at the rate of ¼ ounce per square foot, along with some rotted manure, may be dug into the soil just before planting. Fertilizers that are high in nitrogen or green manure should be avoided, especially in the fall as they cause lush green growth, few flowers, and may cause root rot. In established beds each spring as new growth starts one handful of 5-10-10 or similar formulation of fertilizer may be sprinkled in a circle around each clump, preferably before a rain. In southeastern Ohio iris do not need to be mulched and all mulch should be avoided as it may pack in around the rhizomes and trap moisture and encourage root rot.
If you are willing to put in the effort, bearded iris are truly a beautiful part of a perennial garden with a lovely show of color in June while many other flowers are not yet blooming. Iris are often referred to as the “rainbow flower,” Queen of the Garden, Goddess of the Rainbow, and the Perennial Supreme. Iris will give many years of enjoyment.
For more information on growing iris and other perennials contact the Guernsey County Extension Office at 489-5300 or go online at.