Bearded Iris: Care and Growing Guide

The bearded iris is beloved for its large, showy, fragrant flowers. It has six petals: three upright or standard, three drooping or falling, and a frilly beard in the center that leads pollinators to the pollen-lined and sweet nectar spot. It also has long, strappy, sword-like leaves and some types can grow to a mature height of about 4 feet.

Bearded iris grows best in sandy or well-draining soil conditions with full sun exposure and is somewhat drought tolerant. They can handle a swing of temperatures but will develop root rot if the soil gets soggy or has too much soil moisture; never mulch. The bearded iris easily multiplies so divide them every few years to freshen them up and extend their life cycle. These plants are toxic to dogs and cats.

How to Plant Bearded Iris

When to Plant

Plant bearded iris from nursery starts in the spring and it will flower in its first year. Plant bare roots in the fall or the spring; bare-root plants may not flower robustly until their second year. Bearded irises have a moderate growth rate, growing 4 to 40 or more inches in one year.

Where to Plant

Give bearded irises full sun to grow and well-draining soil. Iris plants can't tolerate clay-like soils. In the hottest climates, the full sun might become too harsh for longer than six hours, so ensure it has some shade cover for a portion of the day. They can tolerate all-day sun in cooler climates, such as in the lower USDA zones 4 and 5.

How to Plant

Plant the rhizome rooting structures about 1 to 2 feet apart. They do not need to be planted too deep. Most iris rhizomes should be planted below the surface, exposing the top with any roots pointed downward. However, in a hot weather climate, at the upper range of USDA zones 7-9, cover the top of the rhizome with 1 inch of soil. Lightly water to settle the soil around the root structure.

Tall bearded irises require staking, especially during high winds or inclement weather. Use a long bamboo stake planted close to the base, but avoid harming the rhizome when digging it into the ground.

Bearded Iris Care

Popular bearded irises are easy to grow provided you plant them in a sunny site with well-draining soil. A major departure for growing irises compared to other perennials is that they do not like mulch. Mulches (as well as deep planting) encourage the rhizomes to develop rot, so let your soil remain bare. Space plants at least 12 inches apart to prevent the need for frequent dividing.

Here are the main care requirements for growing bearded irises:

• Plant in a sunny location.
• Ensure it has well-draining soil.
• Do not layer the top of the soil with mulch (in most zones).
• Only water when the top 2 inches of soil are dry.
• Give low-nitrogen fertilizer in the spring to encourage bloom.
  

Light

Irises need full sun to thrive. In full shade, they produce fewer blooms and may suffer from an increase in diseases.

Soil

Heavy clay soils do not work well for growing iris, but sandy or gravelly soils are excellent. If your native soil is heavy, you can plant your iris bulbs in raised beds to help drainage. To lighten the soil, you may also amend your soil with gypsum or organic matter like compost.

Water

Although irises like moisture, they also need good drainage to prevent rot. Water them when the top 2 inches of the soil feel dry. These plants have a good drought tolerance.

Temperature and Humidity

Irises are notorious for their hardy disposition. They don't mind temperature extremes if the soil allows excess rain or snowmelt to drain away. Irises damaged by heavy winds or hail can be susceptible to iris borer larvae.

Fertilizer

In the spring, apply a low-nitrogen 6-10-10 fertilizer around your irises. Too much nitrogen will encourage foliage at the expense of blooms. Bone meal is also a good fertilizer.

Types of Bearded Iris

Iris groups are categorized as "bearded," "beardless," and "crested." Japanese, Dutch, and Siberian iris are among those that fall into the beardless category. There are also subcategories based on stature and varying bloom times. Look for robust irises to plant that have won awards, such as the Dykes Medal. Here are a few award-winners that are widely grown:

• "Celebration Song": A tall, pink, or lavender bearded iris that grows to 37 inches.
• "Abiqua Falls": This is a true blue tall bearded iris that grows to 39 inches.
• "Again and Again": The yellow, reblooming, tall bearded iris grows to 36 inches.
• "American Classic": This tall iris is white with blue-violet highlights and grows to 36 inches.
• "Beatnick": This dwarf bearded iris grows to 14 inches and has purple flowers with white highlights.
• "Big Blue Eyes": The dwarf bearded iris is white and violet, and grows to 14 inches.
• "Dusky Challenger": This dark purple iris grows to 39 inches tall.
• "Thornbird": This is a beautiful yellow iris that grows to 37 inches.
• "Queen's Circle": An iris with white flowers and blue-lavender fringes grows to 32 inches.
• "That's All Folks": The towering yellow-gold iris grows to 40 inches.
• "Jesse's Song": Another tall violet and white iris, this one grows to 35 inches tall.

Pruning

Faded, withered flowers should be pinched off immediately. Pruning irises may promote additional blooms or even a repeat bloom period later in the season.

Every three to five years, clumps of iris should be dug up, divided, and replanted to cull out diseased roots and iris borer damage. Dividing will keep iris plants vigorous and allow you to propagate new plants.

Propagating Bearded Iris

Dividing irises every few years keeps them healthy and multiplying. Dig up the rhizomes with a shovel in late summer and shake off all loose soil. Carefully pull or cut the rhizome cluster apart into sections, each with a fan of foliage about 3 to 6 inches. Cut away soft, rotten parts of roots or areas that have borer tunnels or worms.

Replant each root section, just barely covering the rhizome, and space roots at least 12 inches apart to quickly fill the space. Water thoroughly upon planting, then weekly until frost sets in. New foliage growth will probably begin in late summer and fall, and the plant will grow vigorously when it returns in the spring.

How to Grow Bearded Iris From Seed

Propagation by seed is typically handled by nursery professionals to breed new varieties by careful cross-pollination. However, you can grow iris from the tiny seeds in the green oval pods left behind after the flowers fade. Collect the seeds and plant them about 1/4-inch deep in the garden, and they will sprout and mature into flowering plants within three years.

Most garden iris are hybrids, and usually do not "come true." The iris plants you propagate by collecting seeds may look quite different from the mother plant.

Potting and Repotting Bearded Iris

Though uncommon, you can grow irises in pots at least 12 inches wide. Use a loose, soil-free potting mix, and leave the tops of the rhizomes exposed or just barely covered. Do not overwater the plants.

In colder climates, move the containers to sheltered locations for the winter. Irises in containers may need dividing and transplanting about every other year.

Overwintering

Trim back foliage fans to about 6 inches in the fall to tidy the garden, reduce leaf surfaces for fungal disease to flourish, and remove caterpillar eggs. Destroy the removed foliage but do not add it to a compost bin.

If plants show signs of rot or damage from borers, dig up the roots in early fall. Cut away diseased or worm-damaged sections and replant the healthy roots several weeks before freezing weather sets in.

Common Pests and Plant Diseases

Though irises do not suffer many problems, routine lifting and dividing are necessary to combat iris borer worms and keep plants healthy.

The iris borer is a serious pest. In the spring, caterpillars hatch and tunnel through leaves, reaching the rhizome by summer, making the plant vulnerable to bacterial rot.

Major disease problems include bacterial soft rot, crown rot fungus, and fungal leaf spot. Mottled leaves and flowers suggest the mosaic virus. Remove and destroy affected plant material (do not compost). Good hygiene is usually enough to control these diseases; fungicides aren't usually needed.

How to Get Bearded Iris to Bloom

Bloom Months

Bearded iris typically blooms in April or May. Some reblooming cultivars may rebloom in summer or fall.

What Do Bearded Iris Flowers Look and Smell Like?

Bearded iris flowers are known for their large, show-stopping flowers. They have six petals—three upright standard petals and three floppy petals that fall downward. The petals have a central, bearded line leading inward to the flower center.

Of the irises, bearded irises are the most fragrant. Some cultivars are more fragrant, with scents ranging from orange blossom to grape soda.

How to Encourage More Blooms

• Proper planting depth: Don't plant the rhizomes too deeply. When replanting divisions, ensure the rhizome crown is barely covered with soil.
• Give ample sun: Ensure the iris gets at least six hours of direct sunlight daily.
• Do not overfeed: Too much fertilizer causes the iris to put energy into leaf growth at the expense of flowers. All it needs is a single feeding in the spring.
• Divide every few years: Flowering will fall off radically when root clumps become too dense. Dig up your irises every few years to divide and replant them.

Common Problems With Bearded Iris

Of the irises, the bearded iris is arguably the most popular and easiest to grow. Bearded irises are largely trouble-free but can develop a few issues.

Leaves Turn Yellow or Brown

Yellowing and browning can be a sign of root rot caused by excessively wet soil or extensive damage from iris borers. Immediately lift affected root clumps, cut away soft, decaying areas, and replant in porous and well-draining soil.

Flower Stalks Topple Over

Some bearded irises grow as much as 40 inches tall, and staking may be required to support the huge flowers. Irises that grow in shady conditions may get even leggier, making staking a necessity.

Leaves Have Yellow and Brown Spots

Spotted leaves are the result of bacteria or fungal infections. Bacterial leaf spot usually begins on the edges of the leaves, gradually enlarging. Fungal leaf spots typically appear on the inner part of the leaves, and they do not enlarge in size. Affected plant parts should be removed and destroyed. Keep the ground around the irises free of mulch and debris. Good garden hygiene usually controls leaf spot diseases. Serious fungal infections can be controlled with fungicides.