Add some irresistible irises to your garden

By Dawn Pettinelli - UConn Home & Garden Education Center
Feature Article - posted Thu., Jun. 2, 2011
- Contributed Photo

Irises have played a prominent part in lore, legend and religion for more than 4,000 years. According to the ancient Greeks, they were the personification of the goddess, Iris, and placed on the tombs of women. Of the more than 200 species, three are most commonly grown in New England gardens. They are the tall bearded, Siberian and Japanese irises.

Iris blossoms vary greatly in shape, color and size, but their overall structure is similar. Each flower consists of three upper petals called standards and three lower or outer sepals referred to as falls. Irises are divided into two major groups; those arising from rhizomes, which are horizontal stems growing at or slightly below the soil surface, and those growing from bulbs.

Some gardeners lament the relatively brief annual flowering period of irises. And it is true that even in good years weather-wise, you cannot expect more than two or three weeks of a spectacular show. These folks can be comforted to some extent by choosing early, mid-season and late species and varieties of irises, so the blooming period is prolonged. I like to think about it more like a special holiday one looks forward to each year. It just wouldn’t be appreciated as much if it occurred more often. And irises are just too magnificent to be taken for granted.

There is an iris suited to just about every location, whether you have a sunny site, part shade, alkaline or acid soil, or wet or dry areas. In general, irises are easy to grow, but an eye-stopping display does take a little work. The older varieties withstand a fair amount of neglect, while the newer hybrids require more attention to reach their full potential.

Taller irises make a nice backdrop for lower growing perennials. Shorter species, like the miniature bearded iris, or the crested iris (Iris cristata) look best planted in drifts in the front of the garden.

As far as the tall bearded irises go, your color choice is virtually unlimited. Lovelier shades become available each year. Also known as German bearded irises, they prefer a sunny, well-drained site with adequate moisture. They reach 2 to 3 feet in height and come into bloom from mid-May through early June.

Siberian irises bloom slightly later than the bearded irises. They also grow from rhizomes but the rhizomes are quite small and they readily form a fibrous root system. Colors of Siberian irises are somewhat limited compared to their bearded cousins. They range from white to blue, purple, violet and wine red. Their foliage is slender, almost grass-like.

Japanese irises flower in early to mid summer and can grow up to 4 feet tall. A fallacy concerning Japanese irises is that they need wet conditions to do well. In truth, they will grow in almost any well-drained, organic, slightly acidic soil as long as adequate moisture is supplied.

Another fallacy is that irises should not be fertilized. Mine seem quite appreciative of nutrients both during early spring growth and about a month after flowering. The bearded irises go into a resting stage after they bloom, which lasts about a month. Then they begin to produce new roots and leaf buds. Each rhizome only produces flowers once and then it retires to function solely as a food reservoir.

Division of bearded irises is best done in late summer. Use a sharp knife to divide the rhizomes, making sure each mature rhizome has one or more new leaf buds attached.

While Siberian irises are rarely bothered by pests, iris borers can be a problem with the bearded iris. Control consists of removal of dead leaves in the fall or early spring. If borer damage is noticed, usually because of zigzag feeding injury on leaves, dig up the clump, find the larvae and dispose of them. It is a good idea to dig and divide bearded irises at least every third year to scout for pests.

If you have questions about growing irises or other home- or garden-related queries, call the UConn Home & Garden Education Center (toll-free) at 877-486-6271, visit or get in touch with your local Cooperative Extension Center.

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