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The Almelund Threshing Show is over for 2008 and hats off to those who plan this event as it gets better and bigger every year. Peggy Boiko put together excellent displays on spiders, apple problems as well as weather related and disease problems of tomatoes. Each day, Richard Hanson brought in different samples of some of his 120 daylily varieties. All of these displays attracted gardeners with many different questions. We had several questions on the transplanting of iris plants, thus the reason for this article. Late August through early September is the time for planting, transplanting, and dividing the iris plants.

If you are preparing a new bed, remember that location is very important. New beds need to be free of debris such as rocks and roots. Work in organic material such as peat moss, fine compost or shredded leaf mulch. This should be worked into a depth of 10 to 12 inches. It may be beneficial to work in some 5-10-10 fertilizer according to the directions on the bag. This must be mixed into the soil very well before planting the bulbs. Plant irises in full sun and space plants at least eight inches apart. Adequate spacing improves air circulation, preventing disease development.

It is a good idea to divide the iris every three to four years. If your iris did not bloom as well as they used to, the problem could be improper soil, not enough sun, or poor soil drainage. These problems can be corrected by moving the plants to a better site or improving the soil.

Iris rhizomes sit just below the surface. To dig up a clump, slide your garden fork carefully beneath the clump and lift it out of the soil. Spread the clump out on the lawn and wash them off with a garden hose. Once you see the rhizomes, it's not difficult to cut each clump into smaller parts for replanting. Each clump of iris will have two or more fans of leaves growing out of the rhizomes. Use a sharp knife to divide the rhizome attached to it. Discard the oldest, woody, part of the original rhizomes, along with any parts that are soft or rotted.

Trim away any broken roots and cut the green foliage back to four to six inches. The divided rhizomes can go right back into the same spot if they haven't been diseased or to a new prepared location. Plant groups with a minimum of eight inches between rhizomes for expansion. They should be placed horizontally right below the surface. Dig a shallow hole for each rhizome, with a small ridge of soil for it to sit on. Spread the roots to both sides of the ridge. Put a light covering of soil over the rhizome and roots and water thoroughly.

The most serious problem for iris growers is the iris borer. The borer hatches from eggs laid on leaves in early spring. The borer goes down the stalk and settles in the rhizome. A sign of iris borer activity could be premature yellow and brown foliage on the entire plant. When you lift up the iris rhizomes, trim away any rotted portions or discard the entire plant. The borer causes a bacterial soft rot that eventually kills the entire plant. A spring spraying of a recommended product when the leaves are five to six inches tall, has been the usual defense. (Parts of this article were taken from an earlier writing by Starr Carpenter, another Chisago County Master Gardener.)

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