What You Need To Know About Growing Irises

These garden must-haves are bearded, beautiful, and full of grace.

June 23, 2016

There are more than 300 species of irises from all the temperate regions of the world and natural hybrids are common. Garden cultivars had appeared in Europe by the 16th century and followed settlers to the New World. A big boom in breeding came after 1830 and by 1939, the American Iris Society (AIS) counted more than 19,000 iris species and hybrids, with more introduced every year.

Here's what you need to know about growing these regal beauties.

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Most Are Bearded

Most irises are bearded and have a complex ancestry that includes an early hybrid, Iris 5 germanica, as well as various European species. What makes them bearded is the fuzz on the falls—which is actually a landing pad for the 10 insects you should actually want around your plants—the three sepals that drape gracefully down beneath the standards, and the three petals that stand up. Newer cultivars are ever more ornate, with elaborate ruffles and intricate patterns of color all across the rainbow.

They're Easy To Grow

Gardeners don't spend much time talking about iris care because bearded irises, especially older varieties, are so easy to grow. They need full sun and well-drained soil that is amply enriched with organic matter such as compost (check out these 7 things you didn't know you could compost). Mulch in cold winters and watering during dry spells can help, but old irises often thrive untended. Irises "don't take much mollycoddling," says Boyce Tankersley, director of living plant documentation at the Chicago Botanic Garden in Glencoe, Illinois. "I don't spray them, I don't fertilize them any more than I fertilize anything else, and they keep coming back and giving me a good show."

Related: 10 Houseplants You Hardly Ever Have To Water

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Planting + Pests 101

Bearded irises are best planted in summer or fall—no later than six weeks before your area's first freeze. Situate the rhizomes—swollen underground stem—just at the soil surface with the roots spread out underneath. When clumps get large, crowded, and flower less, which tends to happen every three to five years, it's best to divide the irises. Just lift the cluster of rhizomes with a garden fork, gently tease it into sections, and replant them, or give some away.

The only serious pest problem is iris borers, which are insect larvae that tunnel through the rhizomes. If you spot them, eradicate the infested plant, and plant different irises somewhere else in the garden.

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Vintage Irises

Just as heirloom tomatoes were rescued by gardeners who love both their flavor and their stories, old irises have found champions. The Historic Iris Preservation Society is dedicated to preserving iris varieties including bearded irises that are more than 30 years old. They're fascinated by older varieties that have simpler, cleaner lines and fewer frills, but usually more toughness and fragrance. These types of irises have fallen out of catalogs, surviving only in old gardens, cemeteries, and other out-of-the-way places.