When to Cut Back Irises for Healthier Plants and More Flowers

Find out when to cut back irises to keep these perennials healthy and looking their best.

Blooming after early spring flowers such as tulips and daffodils fade, irises steal the show both in the garden and in a vase for weeks each spring. But when to cut back irises? After their colorful flowers wither, or should you wait until fall, or even until after winter? This guide explains how and when to cut back irises to encourage healthier plants and more flowers.

When to Cut Back Irises

Bearded irises are the most popular and well-known, but there are also beardless, Siberian, and some native species too. There’s a little variation for when to cut back irises depending on what type they are, but for the most part, there are a few ideal times to get out your pruning shears.

Related: The 12 Best Pruning Shears of 2024 to Keep Your Garden in Check

After Blooming

Don’t cut back the foliage but do cut off the flower stalk. If the foliage is green and healthy, wait until fall to cut it back. Here’s why: the foliage is an energy factory, transforming sunlight and carbon dioxide into glucose and oxygen. The glucose is a key component in developing bigger iris roots, also known as rhizomes. Large rhizomes produce large flowers and a more robust plant. Allow the leaves to stand to encourage a stronger plant to develop.

Do cut back the flower stalk on bearded and beardless iris as soon as the flowers fade. If old flower stalks are allowed to stand, the plant focuses its energy on making seeds for the next generation. By deadheading the flowers, you’ll divert the plant’s energy from making seeds to building a healthy root system.

Unless you want iris seeds (seedlings rarely resemble their parent), cut the bloom stalk back to a couple of inches above ground level. Cutting back the bloom stalks on Siberian iris and other species is not as critical as doing so for bearded iris.

Related: 4 Fun Facts About Irises That Will Make You Love Them Even More

To Remove Unhealthy Leaves

Yellow or brown streaks are signs of a handful of possible problems, from iris borers to iris leafspot to drought. Cut back yellow, streaked, or brown leaves as soon as you notice them. Removing the leaves can help limit the spread of plant diseases or pests. And if the leaves are completely dead, they’re not doing the plant any good so at least removing them will make things look tidier.

Sometimes unhealthy leaves indicate a problem below the soil level so take a moment to examine the rhizomes or roots while you’re cutting back the iris leaves. If any rhizomes are soft or slimy or emit an unpleasant odor, dig them up, carefully separating the infected parts from nearby healthy rhizomes. Continue to check the iris planting for signs of pests or disease weekly.

Tips

Bury any infected plant debris in a deep trench away from your irises or toss it in the trash to avoid spreading plant diseases or pests to more plants in your garden. Never compost infected plant material because conditions may not get hot enough to kill pathogens and pests.

When Dividing Irises

Cut iris leaves back to one-third their length either before you dig up the plant or after you’ve divided the plant and chosen the sections you want to replant. The helps reduce stress on the divided sections as they focus on growing more roots after being replanted. The best time to divide irises is 4 to 6 weeks after they bloom. This will give the newly planted divisions enough time to become well rooted before winter.

Tips

A healthy stand of iris will multiply rapidly. Plan to divide your irises every 3 to 5 years to prevent overcrowding and reduced flowering.

Before Winter

Cutting back bearded iris foliage helps prevent diseases and pests, especially iris borers, from overwintering in the leaves and causing problems next year. In fall, cut the foliage back to 6 to 8 inches above the ground. Cut the leaves at an angle rather than straight across to help water run off the cut surface instead of sit on top, which could encourage rot.

Make sure to clean your pruners with a disinfectant such as rubbing alcohol between plants to avoid spreading existing issues. Bury the foliage in a deep trench away from your irises or toss in the trash.

Frequently Asked Questions

When should you fertilize irises?

Bearded, beardless, and Siberian iris do not need fertilizer. Reblooming types of iris, however, do benefit from fertilizer. Fertilize repeat bloomers with a balanced fertilizer in spring and again after the first flowers of the season fade.

Do irises need to be mulched?

In areas with freezing winters, irises benefit from a 2- to 3-inch-thick layer of mulch the first season after planting. Cover rhizomes with bark mulch, straw, or evergreen boughs after the ground freezes. Remove the covering in early spring to make way for new growth.

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