How To Overwinter Chrysanthemums – Keep Your Autumn Garden Alive
We all love the vibrant, fiery colors that chrysanthemums bring to our gardens as the summer heat fades. You have probably stood in the garden center, admiring those perfect mounds of gold, purple, and bronze, wishing they could last forever.
The good news is that you do not have to treat these stunning perennials as disposable annuals. Learning how to overwinter chrysanthemums is a rewarding skill that saves you money and allows your favorite plants to grow larger and more beautiful every year.
In this guide, I will walk you through the exact steps to protect your mums from the biting frost. Whether you want to keep them in the ground or move them into a cozy garage, I have got you covered with practical, field-tested advice.
Understanding Your Mums: Garden vs. Florist Varieties
Before we dive into the “how-to,” we need to identify what kind of plant you actually have. Not all mums are created equal when it comes to surviving a harsh winter.
Most of the mums you see at grocery stores or floral shops are known as florist mums. These plants are bred for their spectacular blooms and compact shape, but they often lack the underground stolons needed to survive freezing temperatures.
On the other hand, garden mums (often called hardy mums) are the ones we want. These varieties are true perennials that can withstand cold temperatures if given the right care and a little bit of love.
If you planted your mums early in the spring, they have had plenty of time to establish a deep root system. If you just plopped them into the ground in late September, they might need a little extra help to make it through their first winter.
how to overwinter chrysanthemums in the Garden: A Step-by-Step Guide
If you live in a region where the ground freezes, your main goal is to protect the crown of the plant. This is the area where the stems meet the roots, and it is the most vulnerable part of the chrysanthemum.
Follow these steps to ensure your garden mums return with a vengeance next spring:
- Keep Watering Until the First Frost: Many gardeners stop watering once the blooms fade. Don’t do this! Plants that are well-hydrated are much more resistant to cold stress and desiccation from winter winds.
- Stop Fertilizing: You want the plant to slow down and prepare for dormancy. Applying fertilizer in late fall encourages new, tender growth that will simply freeze and die, wasting the plant’s precious energy.
- Leave the Foliage Alone: This is the most common mistake. Do not cut your mums back to the ground in the fall! The dead stems and leaves provide a natural layer of insulation for the crown. Wait until new growth appears in the spring to prune.
- Apply a Heavy Layer of Mulch: Once the ground has frozen, apply 4 to 6 inches of loose mulch. Good options include straw, evergreen boughs, or shredded bark. This prevents the “freeze-thaw” cycle that can heave plants out of the soil.
By leaving the stems intact, you create a structural cage that holds the mulch in place. This setup mimics the natural winter protection these plants would receive in the wild.
The Secret to Success: Dealing with the Freeze-Thaw Cycle
Believe it or not, it isn’t usually the cold itself that kills chrysanthemums. The real villain is a process called frost heaving. This happens when the soil freezes and thaws repeatedly throughout the winter.
When the soil expands and contracts, it can literally push the plant’s root ball out of the ground. Once the roots are exposed to the dry, freezing air, the plant quickly dies. This is why insulation is so critical.
Your goal with mulching is to keep the ground consistently frozen. It sounds counterintuitive, but you want the soil to stay cold rather than warming up on every sunny winter day. A thick layer of straw acts like a thermos, maintaining a stable temperature.
If you notice your mums have popped up out of the dirt during a mid-winter thaw, gently press them back down. Add an extra layer of mulch immediately to prevent further movement.
Overwintering Potted Mums Indoors
Perhaps you live in a very cold climate (Zone 4 or lower), or maybe you have a favorite variety in a decorative pot. In these cases, the best way how to overwinter chrysanthemums is to bring them into a protected space.
Potted plants are more vulnerable because their roots aren’t insulated by the earth. A pot can freeze solid in a single night, killing the root system instantly.
Step 1: Preparation
After the first light frost has blackened the foliage, move your pots into an unheated garage, shed, or basement. The ideal temperature is between 32°F and 45°F. You want the plant to stay dormant, not to keep growing.
Step 2: Light and Water
Since the plant is dormant, it doesn’t need sunlight. However, it still needs a tiny bit of moisture. Check the soil every few weeks. If it feels bone-dry, give it a small splash of water—just enough to keep the roots from shriveling.
Step 3: Spring Re-entry
As the weather warms up in late March or April, move the pots back outside during the day. Gradually acclimate them to the sun and wind. This process, called hardening off, prevents the new growth from getting scorched.
Essential Tools and Materials for Winter Protection
You don’t need a lot of expensive equipment to protect your garden. Most of these items are probably already sitting in your garden shed or can be found for free in your backyard.
- Clean Straw: This is arguably the best mulch for mums because it is lightweight and traps air effectively. Avoid hay, which is full of weed seeds.
- Evergreen Boughs: If you have pine or spruce trees, their branches make excellent covers. They provide protection without smothering the plant.
- Garden Fabric (Frost Cloth): For those unexpected early freezes, a layer of horticultural fleece can save your remaining blooms.
- A Sharp Pair of Bypass Pruners: You will need these in the spring to clear away the old growth once the danger of frost has passed.
Using the right materials ensures that the plant can “breathe.” Avoid using heavy, wet leaves or plastic tarps, as these can trap too much moisture and lead to crown rot, a fungal issue that is often fatal.
Regional Strategies: Adapting to Your USDA Zone
The climate in Georgia is vastly different from the climate in Minnesota. Your approach to how to overwinter chrysanthemums should reflect your local environment.
In Zones 7 through 9, you might not need to do much at all. A light layer of mulch is usually enough. In these warmer areas, the biggest threat is often too much winter rain, which can rot the roots if the soil doesn’t drain well.
In Zones 5 and 6, you are in the “danger zone.” This is where the freeze-thaw cycle is most active. You must be diligent about mulching and leaving the stems intact to ensure survival.
In Zone 4 and colder, overwintering in the ground is a gamble. If you want to try it, choose cultivars specifically labeled as “extra hardy,” such as the Mammoth series developed by the University of Minnesota. Otherwise, the indoor storage method is your safest bet.
Regardless of your zone, always ensure your mums are planted in well-draining soil. Mums hate “wet feet” during the winter. If they sit in soggy soil while dormant, they will almost certainly rot before spring arrives.
Common Pitfalls and How to Avoid Them
Even experienced gardeners make mistakes. Here are a few things to watch out for so your chrysanthemums come back stronger than ever.
Cutting Back Too Early
I know it is tempting to “tidy up” the garden in November. Those dead, brown stems look messy. But resist the urge! Those stems are the plant’s primary defense against the cold. Think of them as a protective skeleton for the crown.
Using the Wrong Mulch
Avoid using whole maple or oak leaves. When they get wet, they mat down into a thick, soggy layer that prevents air from reaching the soil. This is a recipe for fungal diseases. Always shred your leaves first or stick to straw.
Forgeting to Water in Fall
A plant entering winter in a state of drought is much more likely to die. Ensure your mums get about an inch of water per week until the ground actually freezes solid. This helps the roots stay plump and healthy.
Spring Awakening: What to Do When the Snow Melts
The most exciting part of gardening is seeing those first green nubs peeking through the soil in the spring. Once the threat of a hard freeze has passed, it is time to get back to work.
Gently pull back the mulch to allow the sun to warm the soil. This is the time to finally cut back those old, dead stems. Cut them to about 2 or 3 inches above the ground.
As the new growth reaches about 6 inches in height, you can start a light fertilization program. This is also the perfect time to divide your mums. Dig up the clump, split it into smaller sections, and replant them. This prevents overcrowding and keeps the plants vigorous.
Don’t forget the “pinch!” To get that classic bushy shape, pinch off the top inch of each stem every few weeks until the Fourth of July. This encourages the plant to branch out and produce more flowers in the fall.
Frequently Asked Questions About how to overwinter chrysanthemums
Can I overwinter mums that were bought in full bloom?
Yes, you can, but it is more difficult. These plants have put all their energy into flowers rather than roots. To improve their chances, plant them in the ground as soon as possible, water them well, and follow the mulching steps outlined above.
Do I need to dig up my mums every year?
No, not if you live in a zone where they are hardy. You only need to dig them up if you live in an extremely cold climate or if you want to move them to a different location. Most garden mums prefer to stay put once established.
What if my mums start growing in the middle of winter?
If a warm spell triggers new growth, don’t panic. Leave the mulch in place. The new shoots might get nipped by the next frost, but the main crown should remain protected. Don’t encourage the growth by watering or fertilizing until spring is truly here.
Is it better to overwinter them in a garage or a basement?
An unheated garage is usually better because it stays colder. A basement can sometimes be too warm, which might cause the plant to wake up too early. The goal is total dormancy until the outdoor temperatures are safe.
Conclusion
Growing chrysanthemums doesn’t have to be a one-season affair. By taking a few simple precautions, you can transform these autumn favorites into permanent residents of your landscape.
Remember, the key is to protect the crown, avoid the temptation to prune in the fall, and provide plenty of insulation against the winter wind. It might seem like a bit of extra work, but the reward of seeing those massive, flower-covered mounds return year after year is well worth the effort.
Don’t be discouraged if you lose a plant or two along the way—gardening is all about experimentation and learning. Every climate is different, and you will soon find the rhythm that works best for your backyard.
So, grab some straw, leave those stems alone, and get ready for a spectacular show next fall. Your future self (and your garden) will thank you! Happy gardening!
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