Iris plants are stunning perennials that bloom in a rainbow of gorgeous colors. While most varieties thrive in hardiness zones 3-9, they do require some special care when cooler weather hits. Proper winter preparation is key to ensure your irises return healthy and vigorous the following spring.
In this complete guide, you’ll learn all the steps for getting your iris beds ready for winter so your plants survive and prosper
Why It’s Important to Prepare Irises for Winter
Even though iris are considered winter hardy in most climates, providing 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 irises for winter:
- Prevent damage to the rhizomes from extreme cold and freeze/thaw cycles
- Avoid rot issues that can happen if rhizomes sit in wet soil all winter
- Discourage fungal diseases like iris leaf spot
- Stop borers and other pests from overwintering in plant debris
- Reduce pest and disease problems in the spring
- Remove old foliage and prevent viral infections
- 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.
- In colder climates, prepare irises in October or November
- In warmer zones, late November to December is fine
- 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:
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.
Dig Up and Divide Congested Clumps
Overcrowded iris rhizomes will not thrive. After cutting back leaves, dig up any clumps that are congested.
- Use a garden fork to gently lift the entire clump.
- Shake or hose off dirt and remove weeds/debris.
- Cut rhizomes apart with a knife, ensuring each division has roots and a growth fan.
- Replant divisions 15-24 inches apart depending on variety.
- Share extras with gardening friends!
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.
Add Winter Mulch
Once beds are cleaned up, add a winter mulch or insulation:
- Straw or pine needles work well. Avoid hay which may contain weed seeds.
- Leaves also work but avoid thick piles, which mat down and hold moisture.
- Evergreen boughs are another option.
- 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.
Consider Winter Protection
In very cold climates, you may want an extra layer of winter protection:
- Place evergreen branches or twigs over the mulched iris beds.
- Erect temporary barriers around the beds using burlap, cardboard, straw bales or other materials.
- Cover beds with row cover fabric or perforated plastic sheeting. Avoid solid plastic which can lead to rot.
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.
- Stop regular watering after first frost.
- Water sparingly once every 3-4 weeks if winter is very dry.
- The soil should be barely moist, not wet.
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:
- Lightly mulch over the rhizomes with sand, gravel, or quartz chips.
- Use 1-2 inches maximum since the goal is not insulation.
- This helps moderate soil temps and retains a tiny bit of moisture.
Clean Tools
Finally, clean and sanitize your gardening tools after working with the iris beds. This prevents diseases from spreading between plants.
- Use a disinfectant or bleach solution.
- Wipe off soil and plant residues.
- 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:
- Pruning too early or late when plants are still active.
- Leaving fallen leaves and debris in the beds over winter.
- Allowing rhizomes to sit in overly wet soil during dormancy.
- Using solid plastic covers or heavy mulches that don’t allow airflow.
- Failing to clean up congested clumps and overcrowded areas.
- Forgetting to sanitize tools after working with diseased plants.
Caring for Irises in Early Spring
Continue proper iris care in early spring as well:
- Remove winter mulch as soon as new growth starts.
- Cut back any remaining dead leaves close to the rhizome.
- Divide and replant any crowded clumps before bloom season.
- Resume regular watering as plants come out of dormancy.
- Apply an organic fertilizer when new leaves reach 4-6 inches.
With proper winter preparation and early spring care, your irises will burst into gorgeous bloom when warmer weather arrives!
Common Problems if Iris Winter Care is Insufficient
Here are some potential problems to watch for if iris winter care is poor:
- Foliage damage due to extreme cold
- Heaving of rhizomes from freeze/thaw cycles
- Rotting of rhizomes due to excess winter moisture
- Spread of bacterial or fungal diseases
- Infestations of borers, slugs, snails or other pests
- Few or no blooms the following season due to stress
Key Tips for Preparing Irises for Winter
- Wait until after several hard frosts and plants look completely dormant.
- Cut back leaves to 6 inches above the rhizomes.
- Dig up and divide any crowded clumps.
- Discard all garden debris and remove weeds.
- Add 2-4 inches of winter mulch like straw over the beds.
- In very cold areas, place evergreen branches on beds for added insulation.
- Water rarely once heavy frosts commence.
- In spring, uncover beds as soon as new growth appears.
With proper end-of-season care, your irises will thrive in winter and leap into vigorous growth and flowering next spring!
Planting, Growing, and Caring for Irises
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The tall, beautiful iris flower, named after the Greek goddess who rode rainbows, comes in many magical colors. Despite its divine origins, this beautiful flower is rugged, reliable, and easy to grow. Learn to plant and care for irises for long-term success in your gardens.
More than 250 species make up the genus Iris. The most familiar irises are the tall bearded irises (I. germanica), which reach 2 to 3 feet tall. Their distinctive six-petaled flowers have three outer hanging petals (called falls) and three inner upright petals (called standards).
Irises may be a bearded or crested (aka beardless) type. Bearded irises are so-called because they have soft hairs along the center of their falls. The hairs on crested types, like the Siberian iris, form a comb or ridge instead.
Most irises flower from late spring to early summer. Some—mostly bearded hybrids—are remontant, meaning they may flower again later in the summer. The blooming period of Siberian irises tends to follow that of the bearded types.
Irises attract butterflies and hummingbirds and make lovely cut flowers. For iris companions in the garden, look to roses, peonies, and lilies. Read Next
Irises bloom best in full sun, meaning at least 6 to 8 hours of sunlight daily. They can tolerate as little as half a day of sun, but it’s not ideal. Without enough light, they won’t bloom well. Bearded irises must not be shaded out by other plants; many do best in a special bed.
Provide well-draining, fertile, neutral to slightly acidic soil. Loosen the soil to 12 to 15 inches deep, then mix in compost or aged manure. Good drainage is critical: Irises prefer “wet feet, but dry knees.” They will not tolerate wet soil in winter. Learn more about preparing the soil for planting and organic soil amendments.
How to Plant Irises
- Plant bare-root rhizomes (the thick stems) horizontally, with the top exposed and only the roots underground. In areas with particularly hot summers, set the rhizome just below the soil surface.
- Dig a hole 10 inches in diameter and 4 inches deep. Make a ridge of soil down the middle and place the rhizome on the ridge, spreading the roots down both sides. Fill in the hole and firm it gently, leaving part of the rhizome and the foliage uncovered.
- Plant singly or in groups of three, 1 to 2 feet apart, depending on the fully grown plant’s size.
- Soak Siberian iris rhizomes in water overnight before planting, then set them 1 inch deep (2 inches, if the soil is sandy), 2 feet apart. Over a period of years, they will form clumps; divide when blooms get smaller and vigor declines.
- Do not mulch around the rhizome, as this may encourage rot.
- Water thoroughly.
Iris Fall Cleanup for Bearded Iris Plants – do this before Winter
FAQ
Should iris be cut back for winter?
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.
How do you winterize iris plants?
Trim Iris foliage to a height of about 6 inches. A clean garden will help prevent the spread of various fungal diseases and can discourage overwintering pests from building nests. Evergreen boughs or straw make a good winter protection for Iris, particularly in areas with especially harsh winters.
Do iris need to be dug up in winter?
A: Iris plants are best divided after flowering in late spring but no later than August to assure that the roots become adequately established before the onset of cold weather. It is not advisable to remove the rhizomes from the ground and store them indoors for the winter.
How do you prepare an iris bed?
Remove any grass, and dig down at least 12 inches to loosen the soil and remove any roots. The more roots you can remove now, the less grass you’ll deal with later. If you really want to cut down on weeding, outline your bed with an edging strip before you plant.
How to winterize an iris plant?
Winterizing an iris plant is an important step in the gardening process, as it helps protect the plant from cold temperatures and harsh winter weather. Properly preparing the soil before winterizing your iris plant is essential for its health. Here are some tips for how to prepare the soil for winterizing an iris plant. Step 1: Test the Soil
Can Iris grow in winter?
Iris plants are a beautiful addition to any garden. They are hardy and can survive in a variety of climates, including cold winter months. But for optimal growth, you need to make sure that your Iris is getting the right amount of sunlight during the winter months.
How do you keep Iris in winter?
Trim Iris foliage to a height of about 6 inches. A clean garden will help prevent the spread of various fungal diseases and can discourage overwintering pests from building nests. Evergreen boughs or straw make a good winter protection for Iris, particularly in areas with especially harsh winters. Apply after freeze-up.
Do Irises need to be mulched in winter?
Likewise, cold, hardy varieties like Siberian iris and Japanese iris can do with a little mulching during the winter, but you may have to dig out the rhizomes of other varieties and recultivate them come spring. For irises, winter care begins with fall pruning.
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.
How do I prepare my iris rhizomes for winter?
Effective overwintering involves minimizing moisture and providing protection. Bulbous Irises: These require specific winter care to prevent freezing and rot. To prepare your iris rhizomes for winter, follow these steps: Check the Leaves: Ensure the iris leaves are flat and sword-shaped before proceeding.