When and How to Cut Back Iris Leaves After Blooming
By cutting back iris leaves and flower stalks after they finish blooming, you set up next spring’s flowers for even more vigor. Follow along as master naturalist and experienced gardener Sarah Jay walks through the steps for how to cut back irises after blooming.
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In the colder regions of North America, irises typically bloom in June. Where I live, here in Texas and in other warmer areas of the continent, they bloom in late spring and sometimes again in late fall. After they bloom, depending on the type you grow and your preferences, it’s time to cut back irises.
This task is perfect for coupling with others that bolster the health and well-being of your plants in the upcoming season. Whether you have another flourish waiting for you in fall or you have to wait until spring, these small jobs ensure better blooms down the line.
Knowing how and when to do each of the associated tasks helps you develop a regimen that repeats every year. That routine keeps you close to your iris beds, ready to tackle any pests and diseases that may arise. It also offers you the chance to do what you can to make those flowers pop.
Know Your Type
There are so many different irises out there with different habits. Before we get to how to cut back iris leaves, let’s cover a few of the overarching categories. The American Iris Society classifies irises into three main categories. These are bearded irises, aril irises, and beardless irises.
Native to central and southern Europe, bearded types generally bloom from late spring to early summer, depending on the climate and species. Some bloom singly, and others are reblooming. The bearded group includes favorites, like the deep violet ‘Stepping Out’ and peach beauty, ‘Beverly Sills’.
Arils include the oncocyclus, which have one bloom per stalk, and regalia irises which usually have two. While climate is always the determining factor, both tend to have split seasons where they bloom in early spring, and then in fall. These are native to east Asia and include among other species the unique and unusual Iris paradoxa.
Bearless types also bloom somewhere in early spring through early summer. Dwarf types sometimes bloom earlier than this, and not all have split blooming seasons. Iris tectorum or crested iris is a showy, yet irregularly-shaped beardless species. Most are native to Asia, but a small subset is indigenous to North America. This includes the gorgeous lavender wetland dweller, Southern Blue Flag.
Wait for Spent Blooms
Once you’ve determined which type grows in your garden, enjoy their succession of blooms, and wait for them to fade. For bearded and beardless kinds, look for blooms that last through late spring in warmer climates and early summer in cooler areas. Arils typically fade from March through May.
The blooming phase ends when flowers brown and stalks stop producing buds. At this point, the stalk may fall over among the still-standing foliage of the plant. This is possible for all types of iris. Once this occurs, it’s time to act. Get out your pruners and your garden gloves.
If you want to collect iris seeds, skip this step. Be diligent about the remaining steps, though, as they are important for keeping your plants healthy. Irises cross-pollinate, so your seeds may not breed true to type. However, seeing what does grow from the seeds is a fun and rewarding project that could result in you developing a new cultivar.
Clip the Flower Stalk
The process of cutting back irises has many benefits. Not only does this revitalize the plant, and redirect energy to root and foliage growth, it also reduces the likelihood of pests and diseases. This limits the ability of certain fungal diseases to take hold. These set in when areas of the plant decay.
Sterilize your pruners before you get to snipping. You don’t want to carry out a task meant to spare you the ills of pestilence only to spread it unwittingly. Take the flower stem, and trace it back to the base of the plant. Then snip it off as close to the ground as possible.
Remove Browning Leaves
As mentioned, cutting back an iris can help the plant later on. Removing the no-longer-growing parts of the plant limits the potential for pests and diseases that reduce iris vigor. The next thing to do is remove any spent or diseased leaves from the basal clumps. Any that are lying stray in the garden should be taken out too. This stops bacterial, fungal, and viral diseases that reside in downed leaves.
Look for partially browned leaves and use your pruners to snip those off just below the browned area. Feel free to omit the green areas of the plant, as they continue developing, feeding energy to roots. When it comes to diseased leaves, remove these at their base, cleaning your shears with rubbing alcohol or hydrogen peroxide in between snips.
This is a great time to look for water-streaked leaves and chewing damage indicative of iris borer. If they are, plan for a treatment of beneficial nematodes in the following spring before you plant your rhizomes. No matter the type of iris, leave any of the green and supple foliage on the plant. This remains through summer, and promotes stunning fall blooms for rebloomers, or spring ones for single bloomers.
Weed and Clean Up Debris
Diseases like iris leaf spot crop up if too much decaying foliage remains around the base of the plant. This is an unsightly to deadly disease depending on severity. Take out any plants that exhibit signs of ink disease, or black splotches on exposed rhizomes.
After you cleaned up the area, give reblooming types a feeding ahead of their second flowering season. Wait for about a month after the blooms fade, and fertilize them with an organic fertilizer with a 6-10-10 NPK. Many specialized iris fertilizers are formulated this way or similarly.
Cut Back Leaves
Single bloomers typically finish by late summer, while rebloomers produce a second set of flowers in early fall. In areas with pronounced winter seasons, when the first few fall frosts roll in, the once healthy leaves die back. The vegetative parts of the plant dissipate in order for the roots to enter dormancy.
This is the time to cut back iris leaves in preparation for next season. Cut them to ⅓ of their height. If your winter is mild, leave them and cover them with a good dose of mulch to protect the roots from the cold. In areas with consistently frigid winters, lift your roots to overwinter in storage.
Divide Them
As you prepare the rhizomes for storage, look for nodes at the base of the leaves. Observe which ones face the same direction. Use your hands to pull the rhizomes apart in divisions of one to three with leaves facing alongside one another. When you replant them, it will be easier to create a pleasing display with leaves facing the same way.
Then place them in a box with small holes in it to overwinter. Place the box in a cool, dry area with good air circulation. When the danger of frost has passed, plant your rhizomes 12 to 18 inches apart in your garden. Give them plenty of sun, a well-draining and rich soil, and water them so they receive one inch of water per week.
