GROWING IRIS

Irises are an extremely simple perennial to grow in your garden and only require your attention every 2 to 3 years. They are grown from a “rhizome” which continually grow and multiply under ground and need to be divided occasionally to avoid over crowding. When you are ready to grow irises in your garden start with a little soil preparation first. Pick a location that receives plenty of sunshine then work the soil to a depth of 8 to 10 inches. Add some composted manure and bone meal for nutrient value and if your soil is heavy clay, add some course sand or perelite (not vermiculite).

When planting your iris it is important not to plant the rhizome too deep. Get the roots down deep but the rhizome itself should be just barely below the surface. Water thoroughly, and again, water weekly until your iris is established. Be careful at the time of transplanting that you do not allow the rhizome to dry out before planting.

After 2 to 3 years it is time for digging and dividing. Late summer to early fall is the best time for this operation. Using a shovel, simply dig the whole iris out of the ground. With a sharp knife, cut the younger, outward growing rhizomes into sections trying to leave as many of the roots and flowering buds on each piece as possible. Cut the leaves back to one-third of their original height, straight across or at an angle, it does not matter. Re-plant new, younger rhizomes (not too deep) and discard the old ones.

The adult iris borer is a moth that in late August and September lay clusters of eggs on the iris leaves and at the base of the stalks that winter over and hatch in April and early May. The small larvae crawl up on the young leaves and make tiny pinpoints holes as they enter then continue to tunnel their way to the base of the leaves throughout the spring. The damage appears as water-soaked, brownish spots and streaks on the leaves. By early to mid-July the larvae next tunnels into the rhizomes which is particularly damaging to the iris. Then the cycle repeats itself.

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Fall sanitation after the first hard frost as well as insecticides labeled for iris boror and sprayed in the early spring are the best methods for control. Also, dipping the rhizomes in the liquid insecticide at the time of division (late summer/early fall) or simply dusting them at that time is very effective.