SPRING IS HERE — the irises are coming

By Marilyn McKinley

OSU Extension master gardener volunteer

Soon another old-fashioned spring flower will be in bloom — the iris.

This old-time favorite is sometimes called “flags.”

Irises come in a kaleidoscope of colors, and some now are re-bloomers, also blooming in the fall.

I like irises because they are easy-to-grow perennials, versatile, reliable, easy to care for and easy to dig and divide. They are hardy to zone 3, and can adapt to different soils and light conditions.

The first iris to appear in the spring is the dwarf variety. It produces 6-inch-tall blue, yellow or purple flowers. It likes well-drained soil.

Next to bloom is the bearded variety. Its fleshy root is really a rhizome, which grows at the surface of the soil. Its stalks range from about 10 to 40 inches.

Then comes the Siberian irises, which are 2 to 4 feet tall. They usually have blue or white and violet flowers and tall grasslike foliage. It does well in cool and wet conditions. It thrives in the sun but will do well in part shade, too. Plant about 1 inch deep; divide in late summer when the center of the clump stops growing.

Japanese irises thrive in wet, acid, mucky soils. They grow nicely along a pond, stream, or in water gardens. They produce flowers on long stalks, 2-3 feet tall, with a range of color from white to lavender. Leaves are ribbed and upright, producing the largest flower of all iris varieties.

The Dutch variety is perfect for a cutting garden. This hybrid variety often is grown as an annual, can be planted in the fall or spring in our zone. The orchidlike flowers come in a wide range of colors and patterns. The bulbs can be planted in the sun to full shade, 4 inches deep.

Healthy iris plants will need to be divided every three to four years. A decrease in the amount of blooms is a signal that division is needed. Divide bearded varieties two months after blooming. Other types are best divided in the early spring or fall. Before you divide bearded irises, cut foliage to one-third of their original height. Dig the clumps and separate healthy rhizomes from older ones near the center. Cut the new leaves so each has at least one set of leaves or fan. Plant them 12 to 18 inches apart, just under the soil.

The most-serious problem with irises, particularly the bearded variety, is the iris borer. The eggs overwinter, hatch in the spring, tunnel into the leaves and eventually into the rhizomes. The leaves of infected plants will have yellow streaks and easily detach from the rhizome. The rhizome may be mushy or have small holes from the burrowing larvae.

To control this pest, remove foliage and debris around the plant in the fall. Discard infected rhizomes when dividing. Remove and destroy any infected foliage that appears during the growing season.

To learn more, goto: http://go.osu.edu/irises.