How to Overwinter Mums and Keep Them Alive

To overwinter mums successfully, focus on four things: hardiness, establishment, drainage, and root insulation. Hardy garden mums growing in well-drained soil are usually the best candidates to survive winter outdoors. Potted mums need extra protection because their roots are more exposed, while unidentified supermarket or florist mums are harder to predict.

The most common mistake is to think winter survival depends only on how cold the air becomes. With chrysanthemums, repeated freezing and thawing, wet soil, poorly established roots, and exposed containers can be just as important.

If you are unsure whether your mum is hardy enough to overwinter, explore Gardenia’s Chrysanthemum collection or compare Chrysanthemums by hardiness, mature size, bloom season, and growing conditions.

1 First, Know Which Mum You Are Overwintering

You do not need a perfect botanical identification, but you do need to know how much confidence you can place in the plant’s winter hardiness.

• Named hardy garden mum: Usually the strongest candidate for outdoor overwintering when its USDA hardiness range matches your climate.
• Rubellum or heritage chrysanthemum: Often well suited to perennial borders and cold-winter garden use.
• Unnamed supermarket mum: It may be hardy, but winter performance is uncertain without a cultivar name.
• Florist mum: Usually selected for flowering display rather than proven landscape performance.
• Mum in a container: Even a hardy cultivar needs extra protection because the root ball is more exposed to freezing.

2 Gardenia’s Mum Winter Route: Which Method Should You Use?

Gardenia’s Mum Winter Route organizes winter care around the plant’s hardiness, how well established it is, how well the site drains, and how much insulation surrounds the roots.

3 How to Overwinter Mums in the Ground

For an established hardy mum, overwintering in the ground is usually the simplest route. Garden soil provides natural insulation, but chrysanthemums still benefit from protection because their fibrous roots are relatively shallow.

• Keep watering through fall when conditions are dry. Do not let the plant enter winter severely drought-stressed, but avoid saturated soil.
• Avoid heavy late-season feeding. The goal is dormancy, not a flush of tender new shoots.
• Consider leaving stems standing in cold climates. Iowa State recommends leaving old growth in place because research found better winter survival in unpruned mums. Some Extension guidance allows fall cutback after dormancy, so local practice varies.
• Wait until the soil has cooled before mulching. Winter mulch should be applied after the ground has become cold rather than while the soil is still warm.
• Cover the root zone with several inches of loose mulch. Straw or pine needles work well because they trap air without packing tightly.
• Remove excess mulch in spring. As the soil thaws and growth resumes, gradually uncover the crown.

4 Why Freeze-Thaw Cycles Can Damage Mums

A chrysanthemum can suffer winter damage even when the minimum temperature stays within the cultivar’s normal hardiness range.

The problem is often frost heaving. Water in the upper soil freezes, expands, and lifts the soil. When temperatures rise, the soil settles again. Repeated cycles can gradually push shallow-rooted plants upward, exposing crowns and roots to colder air and drying conditions.

Recently planted mums are especially vulnerable because their roots have not yet spread widely into the surrounding soil.

This can explain why:

• An established mum survives while a newly planted one beside it dies.
• A plant can survive a very cold winter with stable snow cover yet struggle during a milder winter with repeated thaws.
• Poorly drained soil can increase winter stress even when the cultivar is technically hardy.

Consistent snow cover can help insulate the soil, while exposed ground that repeatedly warms and refreezes may experience more damaging temperature fluctuations.

This is why USDA hardiness zones are only part of the winter-survival picture. They describe expected minimum temperatures, not drainage, establishment, snow cover, or frost heaving.

5 Should You Cut Mums Back Before Winter?

In cold-winter climates, leaving hardy mums standing until spring is a well-supported approach. Iowa State recommends leaving old growth in place because research found better winter survival in unpruned plants, and some Illinois Extension guidance agrees. Other Extension recommendations allow fall cutback after dormancy, so local practice varies.

If maximum winter protection is your priority – especially for marginally hardy or recently planted mums – leaving healthy stems standing until spring is the more conservative choice. If foliage or stems were seriously affected by disease or pests, remove and discard infected material instead of leaving it around the crown over winter.

Old stems can also help trap snow and mulch around the crown. After new growth appears in spring, cut the dead stems back and remove excess winter protection.

6 How to Overwinter Mums in Pots

A mum hardy in your USDA zone is not automatically equally hardy in an exposed container. Garden hardiness ratings generally assume that roots benefit from the insulating effect of surrounding soil.

In a pot, cold can reach the root ball from the top and sides. The smaller the container, the faster its temperature can change.

There are three practical overwintering routes.

Option 1: Move the Pot to a Cold, Protected Location

An unheated garage, shed, or cold basement can protect dormant mums from severe root freezing while allowing them to remain dormant.

A protected space roughly in the 20-45°F (-7 to 7°C) range can work for many dormant hardy perennials. The plant should remain cold, but the root ball should not experience the full extremes of an exposed outdoor pot.

This is a general protected-storage range for dormant hardy perennials rather than a chrysanthemum-specific temperature requirement; the essential goal is to maintain dormancy while preventing severe root freezing.

• Allow the mum to experience normal fall cooling.
• Move it into protection before severe root-zone freezing.
• Keep the soil slightly moist, not wet.
• Check periodically so the root ball does not dry completely.
• Do not fertilize during dormancy.

Option 2: Sink the Pot into the Ground

Sinking the entire container into garden soil gives the roots much more insulation than leaving the pot exposed above ground.

Bury the pot so the surface of the container soil is approximately level with the surrounding ground, then mulch the area after the soil cools.

This is especially useful when you want to keep the mum in its pot and move it elsewhere the following spring.

Option 3: Protect the Pot Outdoors

If you cannot store or sink the container, move it to a sheltered location away from strong winter winds and intense winter sun. Grouping containers together can reduce exposure.

Larger pots are safer than small nursery containers because the greater volume of soil changes temperature more slowly. Insulating material placed around grouped pots can provide additional protection.

7 How Much Should You Water Mums in Winter?

Winter watering depends on where the plant is being overwintered.

In-ground mums generally need little attention once the soil freezes. Before that point, water during prolonged dry weather so the root zone does not enter winter extremely dry.

Dormant potted mums in a protected garage, shed, or similar location need much less water than actively growing plants. Check the soil occasionally and add only enough water to prevent the root ball from drying completely.

Outdoor containers need closer monitoring because shelter can change moisture dramatically. A pot under an overhang may receive almost no rain or snow, while another exposed to winter storms may become too wet.

The goal is simple: slightly moist and well drained, never saturated.

8 What About Mums Bought Late in Fall?

Late-season mums are harder to overwinter because you may be dealing with two uncertainties at once: unknown hardiness and limited establishment time.

If a named hardy mum is already in the ground, protect it as well as you can and recognize that newly established roots are more vulnerable than those of a plant that has been growing all season.

If the mum is still in a pot, do not assume leaving it fully exposed outdoors is safer. A small container can freeze much more severely than surrounding garden soil. Cold protected storage, sinking the pot, or additional outdoor insulation may all be better options.

If the plant is an unidentified supermarket or florist mum, overwintering is an experiment rather than a guarantee.

For more guidance on whether a potted mum should go into the ground, see Gardenia’s Chrysanthemum growing guides.

9 When and How to Wake Mums Up in Spring

Do not rush dormant mums into growth during the first warm spell.

For in-ground plants, begin removing excess mulch as the soil thaws and severe freezing becomes less likely. Fresh shoots should eventually appear from the crown near soil level.

Once active growth is visible:

• Remove the previous year’s dead stems.
• Pull heavy mulch away from the crown.
• Resume normal watering as needed.
• Begin feeding only after growth is underway.
• Divide overcrowded established clumps in spring if necessary.

For mums stored in a cold garage or shed, gradually reintroduce brighter light and outdoor conditions as growth resumes and severe frost risk passes. Avoid moving a dormant plant directly from cold storage into intense sun for an entire day.

Once garden mums are actively growing, normal spring and summer care resumes. For complete care guidance, see Gardenia’s Chrysanthemum Growing and Care Guide.

10 Why Mums Sometimes Die Despite Winter Protection

Winter protection reduces risk, but it cannot correct every underlying problem.

The pattern is the same throughout this guide: successful overwintering depends on the interaction of hardiness + establishment + drainage + root insulation. Winter protection works best when those four factors are already working in the plant’s favor.

11 Make Next Winter Easier

The easiest mum to overwinter is one that was well matched to your garden before winter began.

For more dependable perennial performance, choose named cultivars with documented hardiness, plant them early enough to establish, and give them sunny, well-drained sites.

12 References and Further Reading

The recommendations in this guide draw on current university Extension guidance for chrysanthemum winter survival, frost heaving, mulching, pruning, and overwintering hardy perennials in containers.

• Iowa State University Extension and Outreach – How Should I Prepare Mums for Winter? Guidance on shallow chrysanthemum roots, freeze-thaw cycles, winter mulch, leaving stems standing, and spring cleanup. Prepare Mums for Winter
• Iowa State University Extension and Outreach – Growing Chrysanthemums in Iowa: Detailed guidance on hardiness, establishment, winter survival, pruning, and mulching. Growing Chrysanthemums in Iowa
• Iowa State University Extension and Outreach – What Is Frost Heaving and How Do I Prevent It? Explains how repeated freezing and thawing affects shallow-rooted perennials. Preventing Frost Heaving
• University of Illinois Extension – Planting and Maintaining Perennial Mums: Guidance on establishment, winter mulch, old growth, and spring care. Planting and Maintaining Perennial Mums
• University of Illinois Extension – Overwintering Potted Plants: Guidance on protecting perennial roots in containers, cold storage, sinking pots, grouping containers, and winter moisture. Overwintering Potted Plants

13 The Bottom Line

The best way to overwinter mums is to protect the roots from winter stress. Established hardy mums are usually safest in well-drained garden soil, while potted mums need extra root insulation or cold protected storage.

Use Gardenia’s Mum Winter Route – hardiness + establishment + drainage + root insulation – to choose the winter strategy that fits your plant.

Updated: September 2026 • Reviewed by Gardenia Editors