Iris are stunning perennial flowers that bloom in a rainbow of colors. While most varieties thrive in zones 3-9, they do require some special care when cooler weather hits. Proper winter preparation is key to ensure your iris return healthy and vigorous the following spring.
Here is a complete guide on how to get your iris beds ready for winter so your plants survive and prosper.
Why Prepare Irises for Winter?
Iris are considered winter hardy in most climates. However, some protection and dormant season care will help them weather the cold months and re-emerge beautifully in spring.
Here are the key reasons for preparing iris for winter:
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Prevent damage to the rhizomes from extreme cold and freeze/thaw cycles
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Avoid rot issues that can happen if rhizomes sit in wet soil all winter
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Discourage fungal diseases like iris leaf spot
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Stop borers and other pests from overwintering in plant debris
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Reduce pest and disease problems in the spring
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Remove old foliage and prevent viral infections
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Promote vigorous, healthy new growth when blooming resumes
When to Prepare Iris Beds for Winter
The best time is late fall after the first hard frost. This is when the leaves have turned completely brown and the plants are going dormant.
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In colder climates, prepare iris in October or November
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In warmer zones, late November to December is fine
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Avoid pruning too early while plants are still semi-active
The precise timing will vary depending on your local climate and weather. Just wait until the plants look completely dried up and defunct for winter.
Step-by-Step Guide to Preparing Irises for Winter
Follow these simple steps to properly clean up and protect your iris rhizomes before winter:
1. Cut Back Leaves
The first step is cutting back the remaining iris foliage to about 6 inches above the ground. Removing the dead leaves eliminates places where diseases and pests can overwinter.
Use clean, sanitized pruning shears or garden scissors. Make cuts on an angle near the base of each leaf fan.
Discard the cuttings – do not compost diseased foliage.
2. Dig Up and Divide Congested Clumps
Overcrowded iris rhizomes will not thrive. After cutting back leaves, dig up any clumps that are congested.
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Use a garden fork to gently lift the entire clump.
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Shake or hose off dirt and remove weeds/debris.
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Cut rhizomes apart with a knife, ensuring each division has roots and a growth fan.
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Replant divisions 15-24 inches apart depending on variety.
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Share extras with gardening friends!
3. Clean Up Debris
Remove all the leaf cuttings and debris from the iris beds. Take out weeds, sticks, and rocks. Eliminate places where slugs and snails can hide.
A clean garden discourages diseases and pests. It also lets new foliage emerge unimpeded in spring.
4. Add Winter Mulch
Once beds are cleaned up, add a winter mulch or insulation:
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Straw or pine needles work well. Avoid hay which may contain weed seeds.
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Leaves also work but avoid thick piles, which mat down and hold moisture.
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Evergreen boughs are another option.
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Apply 2-4 inches of mulch over the tops of rhizomes after soil freezes.
The mulch helps moderate soil temperatures, prevents frost heaving, and keeps the rhizomes drier over winter.
5. Consider Winter Protection
In very cold climates, you may want an extra layer of winter protection:
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Place evergreen branches or twigs over the mulched iris beds.
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Erect temporary barriers around the beds using burlap, cardboard, straw bales or other materials.
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Cover beds with row cover fabric or perforated plastic sheeting. Avoid solid plastic which can lead to rot.
6. Water Sparingly After First Freeze
Once heavy frosts commence, iris plants become dormant and require very little moisture. Too much winter water promotes rot in the rhizome.
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Stop regular watering after first frost.
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Water sparingly once every 3-4 weeks if winter is very dry.
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The soil should be barely moist, not wet.
7. Apply Loose Winter Mulch
In warmer winter areas, a winter mulch may not be necessary. But a very thin layer of loose material can still be beneficial:
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Lightly mulch over the rhizomes with sand, gravel, or quartz chips.
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Use 1-2 inches maximum since the goal is not insulation.
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This helps moderate soil temps and retains a tiny bit of moisture.
8. Clean Tools
Finally, clean and sanitize your gardening tools after working with the iris beds. This prevents diseases from spreading between plants.
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Use a disinfectant or bleach solution.
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Wipe off soil and plant residues.
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Let tools dry completely before storing for winter.
Repeat this routine in late winter just before new growth emerges.
What to Avoid When Preparing Irises for Winter
When getting iris ready for colder weather, be sure to avoid:
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Pruning too early or late when plants are still active.
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Leaving fallen leaves and debris in the beds over winter.
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Allowing rhizomes to sit in overly wet soil during dormancy.
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Using solid plastic covers or heavy mulches that don’t allow airflow.
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Failing to clean up congested clumps and overcrowded areas.
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Forgetting to sanitize tools after working with diseased plants.
Caring for Irises in Early Spring
Continue proper iris care in early spring as well:
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Remove winter mulch as soon as new growth starts.
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Cut back any remaining dead leaves close to the rhizome.
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Divide and replant any crowded clumps before bloom season.
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Resume regular watering as plants come out of dormancy.
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Apply an organic fertilizer when new leaves reach 4-6 inches.
With proper winter preparation and early spring care, your iris will burst into gorgeous bloom when warmer weather arrives!
Common Issues With Irises in Winter
Here are some potential problems to watch for if iris winter care is insufficient:
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Foliage damage due to extreme cold.
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Heaving of rhizomes from freeze/thaw cycles.
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Rotting of rhizomes due to excess winter moisture.
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Spread of bacterial or fungal diseases.
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Infestations of borers, slugs, snails or other pests.
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Few or no blooms the following season due to stress.
Key Tips for Preparing Irises for Winter
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Wait until after several hard frosts and plants look completely dormant.
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Cut back leaves to 6 inches above the rhizomes.
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Dig up and divide any crowded clumps.
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Discard all garden debris and remove weeds.
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Add 2-4 inches of winter mulch like straw over the beds.
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In very cold areas, place evergreen branches on beds for added insulation.
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Water rarely once heavy frosts commence.
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In spring, uncover beds as soon as new growth appears.
With proper end-of-season care, your iris will thrive in winter and leap into vigorous growth and flowering next spring!
Cutting Back Iris For Winter
In late fall, cutting back the old top growth is a good way to keep this perennial from getting the most common pests and diseases. Irises with and without beards both have leaves that turn yellow at the end of summer and are mostly dead by the first frost of fall. Bulb-shaped plants lose their leaves early in the spring, but they should be left up as long as possible. This is the time when the bulb stores energy for next season’s blooming. Cut the leaves off until they are 4 to 6 inches above the soil. If there are no signs of disease or pests, compost the leaves. More of the iris’s leaves will fall off as it goes into dormancy, and they will break down in the garden over the winter.
Protecting Iris in Winter
Iris can handle being left in the ground all winter as long as the soil drains well and doesn’t flood in the winter. Bearded iris rhizome can be dug up in the fall, after the plant has lost all of its top growth, if you have winter drainage problems. Rinse the rhizome under running water to get rid of extra soil and any bugs that might be trying to spend the winter on the roots. Let the rhizome dry overnight in a plastic box or on a rack so that air can flow around the roots. Loosely wrap the roots in newspaper and pack them in a shallow layer. Place the box in a dark, frost-free spot over the winter. Check the rhizomes once a month for any pests or mold growing on them. The rhizomes should already have green growth coming out of the top when the garden soil is ready to work in the spring.
Irises that are left in the ground over the winter will do better in USDA growing zones 3 through 6. Cover the growth crown and root zone with coarse sand, evergreen bows, or arborist chips. Ensure that excess mulch is removed from the crown once the plant resumes growth in the spring. Iris borers may be able to spend the winter in heavier mulches like compost or shredded leaves, so they shouldn’t be used.
Iris Fall Cleanup for Bearded Iris Plants – do this before Winter
FAQ
Should iris leaves be cut back for winter?
How do you winterize iris?
How do you prepare an iris plant for winter?
Fertilizing is one of the most important steps in preparing an iris plant for winter. The type of fertilizer used will depend on the condition of the soil, the type of iris, and other factors. For best results, start by testing the soil to determine the current nutrient levels.
How do you take care of irises in winter?
Cut down the leaves to within 4-6 inches of the soil, and compost if there are no signs of disease or pests. As the iris goes further into dormancy, the rest of the foliage will fall off and decompose in the garden over winter. Irises that are left outside in containers may need to be moved out of the path of prevailing winter winds.
How do I prepare my Iris?
In preparing the iris, first, you need to make sure that the iris you are planting is appropriate for weather conditions, deadhead your iris every few weeks, cut down any diseased or damaged plants, place a layer of mulch, water sparingly, fertilize only when necessary, and mulch again in the spring to help keep the soil warm and moist.
Are iris plants ready for winter?
Tips For Preparing Your Irises For Winter Weather. Winterizing iris is an important part of keeping your garden healthy and blooming each spring. With the right preparation, you can ensure that your iris plants will survive the cold winter months and be ready to burst into life come springtime.