When to Cut Back Irises for More Beautiful Blooms Next Spring

It’s no surprise that irises are one of the most popular landscape flowers among gardeners. Their showy blooms come in a rainbow of colors and carry a subtle floral fragrance. Most iris varieties flower from late spring to early summer, bringing pops of color to garden spaces and flower vases.

While irises are fairly easy to grow, knowing when to cut them back can maximize the plant’s health and long-term success. Here, our garden experts share helpful tips on when and how to cut back irises for peak performance and optimum health.

The Importance of Cutting Back Irises

Cutting irises back allows for bountiful blooms and helps mitigate pressure from disease and pests. “Fungal and bacterial pathogens such as rust and leaf spot can carry over onto old foliage, and a major iris pest, the iris borer, may lay its eggs on the leaves to overwinter,” says Britta Johnson, perennials manager at Plants Unlimited.

When and How to Cut Back Irises

There are a few times when you should cut back irises, including after they bloom, before winter, during division, and when the leaves wilt or brown. 

After Flowering

As soon as the blooms fade, cut the flower stalk at the stalk base on an angle using sharp pruners, says Eric Nieusma, co-owner of Maine Hill Farm. Wait to cut back healthy foliage until the fall. The foliage converts sunlight and carbon dioxide into glucose and oxygen, which creates larger rhizomes. (A rhizome is a thick horizontal underground stem that stores food produced by the plant's leaves). Larger roots mean larger iris blooms and better plant vitality the following year.

Before Winter

After a frost (but before winter), cut the Iris foliage back 6 to 8 inches above the ground. “Cut the leaves at an angle rather than straight across,” says Nieusma, similar to a fan shape. This angled cut allows for water run-off, which helps prevent diseases that form from excess moisture.

Cutting back your irises before winter helps protect them from certain pests and diseases. For example, iris borer is a common iris pest that overwinters its eggs in spent leaves. Signs of infestation include vertical streaks in the leaves.

Related Stories

How to Divide Irises for an Everlasting Supply of Blooms

How to Divide Irises for an Everlasting Supply of Blooms

When Foliage Is Unhealthy

Remove brown, yellowing, streaked, and spotted leaves by cutting them off as close to the ground as possible. “Where there is unhealthy foliage present, there could be an underlying problem such as pests or disease,” says Nieusma. After removing unhealthy leaves, carefully inspect the rhizomes; if they are soft or slimy, carefully dig them up and discard them in the garbage. Do not compost the compromised rhizomes, as this could spread disease.

When Dividing

Cut iris leaves back one-third of their length before you dig up the plant or after you've divided it. "The best time to divide the iris plant is 4 to 6 weeks after they bloom, giving it enough time to establish a strong root system before winter," says Nieusma.

In Late Summer

In late summer, iris plants can become disheveled-looking and even flop over. When this happens, Nieusma recommends cutting the entire plant back. “Trim the Iris leaves down to half of their height,” he says. This improves air circulation around the rhizomes and discourages future rot.