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Saturday, June 02, 2001

By Ellen Speicher, Phipps Conservatory and Botanical Gardens

One of my earliest memories as a young child was the intoxicating smell of the tall bearded irises in my parents' garden. These early summer flowers immediately attracted my attention with their large, unique blossoms, and strong aroma. As I grew older, I learned that this iris is only one of many types of beautiful irises that can be enjoyed in the garden.

	Correctly planted irises are bothered by relatively few pests. (Douglass Oster, Post-Gazette)

Irises, often called flags, are a wonderfully diverse group of plants. There are nearly 300 species of irises, ranging from a few inches in height to more than 3 feet. Some species of irises, such as the tall bearded ones, grow from rhizomes, which are large, fleshy horizontal stems. Others grow from bulbs. Irises also come in a wide variety of colors, and their bloom periods range from early spring to fall.

One small, early-blooming variety is Iris reticulata, whose vivid flowers emerge with the earliest crocuses in early spring. A small iris that grows from a bulb, it reaches only 4 to 6 inches high.

Another dwarf iris is Iris pumila, the small bearded iris. It grows from rhizomes and is similar in appearance and care to the much larger tall bearded iris. It grows 8 inches and blooms in early spring soon after Iris reticulata.

A must-have is Iris ensata, the Japanese iris. Unlike the bearded and dwarf irises that need well-drained soil, this one thrives in wet areas. Planted in a low area of the yard that stays damp this rhizomatous iris will bloom with large magnificent flowers in midsummer.

When purchasing irises, choose rhizomes or bulbs that are firm and free of soft spots. Bulbs should be planted 2 to 4 inches below the surface in loose, well-drained soil in a sunny part of the garden. Clumps can be divided and replanted in early autumn. Rhizomes also need a sunny site but should not be completely covered by soil. When planted, the top of the rhizome should remain visible. Be careful to determine whether your rhizomatous iris needs well-drained or wet conditions.

Irises that are planted correctly in the proper site are bothered by relatively few pests and diseases. The most common problem arises from irises that are planted in the wrong conditions. Irises that need well-drained soil but are planted in a wet or shady area will soon rot.

	Growing with Phipps Previous articles in a series Mixture must be in tune with plant All-America Selections For 2001 This is one of a series of periodic columns by staffers of Phipps Conservatory and Botanical Gardens. Ellen Speicher is Phipps' head of horticulture.

One common pest is the iris borer. This pest is a moth larvae which feeds on iris foliage and rhizomes. The larvae hatch from eggs that are laid on the iris foliage in September and October. When the larvae emerge in April and May, they begin feeding on the young iris foliage and slowly eat their way into the rhizome. Ragged edges and streaked or watery areas on new foliage in May or June is a sign of iris borers.

At this stage, borers can be controlled by removal of the infested leaves. By July, the borers reach the rhizome, where their feeding creates a soft rot. Inspect rhizomes and destroy any soft rhizomes found. The best way to prevent iris borers is to remove and destroy the previous year's dead foliage by the end of March. This removes the eggs from the garden before the larvae can hatch.

Many irises will grow rapidly and form large clumps within a few years. Rhizomatous irises can be divided four to six weeks after they finish blooming. Cut back the leaves, leaving about 8 inches of foliage attached to each rhizome. Dig the rhizomes and check them carefully for soft spots. Any part of the rhizome that feels soft should be broken off and discarded. The larger rhizomes from along the outer edges of the clump will produce the most flowers. Older rhizomes in the middle of the clump can be discarded. Replant the irises, spacing the rhizomes about 12 inches apart.

Irises are a beautiful addition to any sunny garden. With the many species of iris that are available, gardeners can enjoy the sight and smell of blooming irises from early spring until fall.

Bibliography:

"Irises: A Practical Gardening Guide" by Karen Glasgow. Timber Press, Portland, Ore.

"Irises: A Romantic History with a Guide to Cultivation" by Susan Berry. Running Press, Philadelphia.

"The Gardener's Iris Book" by William Shear. The Taunton Press, Newtown, Conn.