Iris

The spring is a great time for our gardens. Plants are starting to wake up from a long winter dormancy and it allows us to get outdoors once again to break the cabin fever. One of our early blooming perennials in the spring is Iris.

About Bearded Iris

Bearded Iris, Iris x, is a perennial plant that we grow from a rhizome, an underground running stem. There are over 200 different species and many varieties of Iris within those species giving many options for color, size, and blooming habit. The flower is comprised of 3 outer flower petals, called falls, and 3 inner flower petals, called standards. The standard petals tend to stand more upright while the fall petals droop downward. This iris is called bearded iris because there is a thick, bushy “beard” on the flower falls. Bearded Iris have fans of bright green, sword-shaped leaves.

Varieties

There are tons of different varieties of Iris to choose from. They range from 2-8 inches tall up to 40 inches tall. They have slightly different bloom periods and some can even rebloom in the fall. The color range is vast with many color combinations and even some with ruffles on the edges of the petals. Look through garden catalogs and local nurseries to find the variety that best fits your needs. You might also look for local iris exchange activities where groups get together to divide their iris to obtain new colors for their landscape.

Dividing Iris

Bearded Iris are grown from a rhizome, which is an underground running stem. We plant a piece of a larger rhizome from division to get new plants that look just like the parent plant. Every 3-5 years, Iris plants need to be dug and divided to prevent a dead plant center and to encourage more vigorous flowering. If you aren’t sure when to divide, when the plant develops a dead center or when the rhizomes start showing above ground is a good time to dig and divide the plant. This is an easy task, just dig the plant and use a sharp spade to cut the rhizomes apart. Each division should have a fan of leaves and a section of rhizome. Cut the leaves back by two-thirds before replanting. Replant newly divided plants and share extras with friends and family. It is fun to switch with friends to gain many new colors and sizes and bloom times. Transplanting and dividing Iris should be done in late summer to early fall with July through early August being the best time.

Growing Conditions

Bearded iris plants prefer to grow in full sun with well drained soils. Often, these plants will grow very well in a rock garden and can be damaged in excess moisture. Iris plants bloom early in the spring and give us a green, thick, grass-like texture through the rest of the year. Leave the foliage on the plant through the growing season so plants can build sugars throughout the summer to store in their roots to use for blooming early the next spring. If desired, the flower stalks can be removed after blooming to clean up the plants, but the leaves should be left until they turn yellow in the fall.

Pests of the Iris Bed

Grasses are a common pest of iris beds. It can be fairly difficult to remove grasses once they have moved into our iris beds. The grass can also be moved with the iris’ as they are divided and relocated. Mulching around the iris plants can help to stop the grass from moving in or becoming established. There are selective herbicides that can be used that won’t harm the iris which are those that contain fluazifop, which is commonly found in Grass-B-Gon among others.

Iris Borer is another common pest of iris and is the most destructive pest. Borers feed through the leaves an into the rhizomes causing water streaks in the leaves. The feeding in the rhizomes can kill the plant. The best way to control iris borer is by cleaning up the leaves in the fall to disrupt the egg laying portion of the life cycle of the borers. You can also use an insecticide in late April through early May to reduce the damage. Insecticides with bifenthrin, cyfluthrin, permethrin, or spinosad can be used. Follow-up with a second application 10-14 days later. Or use a single application of a systemic insecticide such as one containing imidacloprid.

Iris Leaf Spot is common in iris plants. The leaf tips will get small brown spots with a water-soaked margin or a reddish-brown margin. These spots can quickly multiply turning into mostly brown leaves. It can decrease the vigor in the plant and can cause early leaf dieback. This is a problem disease in wet seasons or where the iris is not planted in full sun or with correct spacing. Fall clean-up of iris should provide control for this disease in most situations. Division will help with better airflow to reduce the disease.

Bearded Iris plants are a great addition to many landscapes. Because there are hundreds of varieties to choose from, anyone can find the right size, color, and blooming preference to fit their landscape. They are great plants to divide and share with your friends as they grow. Swap your color of Iris with flowers of a different color from a friend or family member so you can both increase the flower variation at your home. So the next time you are looking for a plant for great spring color, choose Iris.

*Reference to commercial products or trade names does not imply endorsement by Nebraska Extension or bias against those not mentioned.

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