Bearded Iris

Generally easy to grow, full sun, and well-drained soil are essential. Excellent drainage will aid in preventing bacterial soft rot. Although some cultivars are expensive, iris is an excellent plant to share among neighbors as it multiplies rapidly. Bearded iris in the perennial border should be divided and replanted in midsummer. The bearded iris has a fleshy rhizome or stem which grows along the surface of the soil. New side buds are developed each year until a large network of branched rhizomes is established. If large blooms are desired, the plants should be divided and replanted every three to five years, depending on the density of the clump. Iris not only flowers poorly when overcrowded, but also is more susceptible to disease and attack by iris borers. The best time to divide is immediately after the blooming season is completed. The operation may be delayed until fall, but summer is preferred. When clumps are divided at this time, the new plants will be well established before winter and ready to produce a fine crop of flowers next spring.

In preparing to replant bearded iris, cut the leaves back to about 6 inches. Then, with a pointed shovel, dig around all sides of the plant and lift the entire clump out of the ground. Wash away the soil. With a sharp knife, cut off the short side branches that have a cluster of leaves at the end. Discard the old center portion of the clump.

Inspect each rhizome for signs of insect feeding or decay. The most serious insect pest of iris, the iris borer, is often found at this time. Check the rhizome for the pinkish, 1 1/4-inch larvae with a row of black spots down the sides, and check the soil for the inch-long borer pupae. Destroy any that are found. Rhizomes infested with borers may also be infected with bacterial soft rot. Remove diseased areas with a knife. If extensive rot is present, discard the entire rhizome. The bottom of the rhizome may have a very uniform pattern of holes where old roots have died. If you see such repetitive patterns in nature, you can feel reasonably sure that it is not a disease or insect problem.

Replant the new divisions after cutting the feeder roots back to about 2 inches. If feeder roots are broken, new roots will develop quickly. Set rhizomes 12 to 15 inches apart. Plant in well-drained soil, and cover about 1 inch deep. In heavy or poorly drained soils, the top of the rhizome should be exposed to reduce the possibility of rot.

After the planting operation is completed, apply a side dressing of 5-10-5 fertilizer at the rate of about 2 pounds per 100 feet of row. Scratch the fertilizer into the top inch of soil and water thoroughly. Apply a very light mulch of sawdust or shredded leaves to conserve soil moisture. Do not use a heavy mulch which may increase the possibility of rhizome rot. Additional water may be needed every two weeks during periods of drought.

After the ground has frozen, apply additional mulch. This will conserve moisture and help prevent the alternate freezing and thawing of the soil that may push plants out of the ground.

Irises grown from divisions should bloom the next spring after planting. For a quick flower display, plant three individual rhizomes 8 to 10 inches apart. But remember, the closer together iris rhizomes are planted, the sooner they will need to be divided.

The same planting procedure is suggested for dwarf and intermediate bearded irises. Try some of these shorter types to add new interest to the garden. Dwarf varieties bloom in early spring, followed by the intermediate, and then the tall types. Some of the intermediate varieties produce a second crop of flowers in the fall.