How do I winterize chrysanthemums? - Plant Care Guide

To winterize chrysanthemums, you need to protect them from freezing temperatures, especially in colder climates, to ensure they return beautifully next spring. The best approach depends on whether your mums are true garden perennials or less hardy florist varieties, and if they are planted in the ground or in pots. Proper timing and mulching are key steps for successful overwintering.

What is Winterizing and Why Do Chrysanthemums Need It?

Winterizing refers to the process of preparing plants for the cold, harsh conditions of winter to help them survive and return robustly in the spring. For chrysanthemums (often called "mums"), this preparation is crucial because most varieties, especially the popular garden mums, are perennials that can thrive for years if adequately protected from freezing temperatures.

Here's why chrysanthemums need winterizing:

• Cold Hardiness Varies: While many garden mums are technically hardy in USDA Zones 5-9 (some even Zone 4 with protection), their root systems are relatively shallow. Extreme cold, repeated freezing and thawing cycles, or wet winter conditions can easily damage or kill these shallow roots.
• Protection from Freezing: The primary goal of winterizing is to insulate the plant's crown and roots from direct freezing. A strong, sustained freeze without protection can cause the water in plant cells to freeze, expanding and rupturing the cell walls, which leads to irreparable damage and plant death.
• Preventing Heaving: In many regions, the ground goes through cycles of freezing and thawing throughout winter. This phenomenon, known as "frost heave," can push shallow-rooted plants like mums out of the soil, exposing their crowns and roots to damaging cold and dry air. A good winterizing strategy helps anchor the plant in place.
• Moisture Management: While some moisture is needed, excessive winter wetness combined with cold can lead to rot, particularly around the plant's crown. Winterizing often involves strategies to ensure good drainage.
• Energy Conservation: By providing insulation, the plant expends less energy trying to protect itself from the cold, allowing it to conserve resources for new growth in spring.
• Ensuring Return Bloom: Without proper winterization, your beloved mums, which provide vibrant fall color, might not survive to bloom again next year. Winterizing is an investment in future floral displays.

In essence, winterizing chrysanthemums is about providing a protective buffer against the severe environmental stressors of winter, ensuring the plant's survival and vigor for the following growing season.

When is the Best Time to Winterize Chrysanthemums?

The best time to winterize chrysanthemums is crucial for their survival and depends on your local climate and the specific conditions they're experiencing. Acting too early or too late can be detrimental.

Here's the ideal timing:

• After They Finish Blooming: Wait until your chrysanthemums have completely finished their flowering cycle. This usually means their blooms have faded, browned, and the foliage might be starting to look a bit tired or frosted.
• After the First Few Hard Freezes: Do NOT cut back or heavily mulch your mums immediately after the first light frost. This is a common mistake. Mums use the energy from their leaves even after a light frost to prepare their root systems for winter. It's best to wait until the foliage has been killed back by several hard freezes (temperatures consistently dipping below 25°F or -4°C). This usually occurs late in the fall, often late November or early December in many temperate regions.
  • Waiting ensures the plant has stored maximum energy in its root system.
  • It also signals the plant to go into full dormancy.
• Before Consistent Hard Freezing or Snowfall: Once you've had a few hard frosts and the foliage has died back, you should aim to get your winterization steps done before the ground freezes solid for the winter or before heavy, insulating snow covers the ground. This typically gives you a window of a few weeks in late fall.

Timing Considerations:

• Early Winterizing (Cutting Back Too Soon): Cutting back the foliage too early, especially before a hard frost, can send a mixed signal to the plant, potentially stimulating new growth that will then be killed by the cold. This wastes the plant's energy. Early mulching can also trap warmth and moisture, potentially preventing the plant from going fully dormant or encouraging fungal issues.
• Late Winterizing (Waiting Too Long): If you wait until the ground is already deeply frozen or covered in heavy snow, it will be much harder to apply protective mulch. The plant may also have already sustained significant damage from the cold.

By observing your specific plant and local weather patterns, you can pinpoint the optimal time to winterize your chrysanthemums, giving them the best chance to thrive through the cold months.

How Do I Winterize Garden Mums Planted in the Ground?

Winterizing garden mums planted in the ground primarily involves protecting their shallow root systems from freezing and thawing cycles. These steps are crucial for ensuring your perennial chrysanthemums return vigorously next spring.

Here's a step-by-step guide for ground-planted mums:

1. Wait for Hard Freezes: As discussed, allow your mums to complete their blooming cycle and experience several hard frosts. The foliage should be visibly browned and dying back. This signals the plant to send energy to its roots for winter storage. Do not cut them back immediately after the first light frost.
2. Cut Back Foliage (Optional, but Recommended for Health): Once the foliage has completely died back and browned (typically late fall/early winter):
   • Using clean, sharp pruning shears, cut the stems back to about 4-6 inches from the ground.
   • Why: This helps prevent diseases and pests from overwintering in the old foliage. It also makes it easier to apply mulch.
   • Alternative: Some gardeners prefer to leave the stems intact until spring, arguing that the old stems provide additional insulation. While this might offer minimal insulation, removing them generally promotes better plant health and reduces disease risk. If you choose this, definitely cut them back in early spring before new growth appears.
3. Ensure Good Drainage: Mums hate sitting in soggy soil over winter, which can lead to crown rot.
   • If your soil is naturally heavy clay, consider mounding soil slightly around the base of the plant to improve drainage.
   • Ensure the planting spot doesn't collect standing water.
4. Apply a Thick Layer of Mulch: This is the most critical step for insulation.
   • When: Apply the mulch after the ground has frozen solid for the first time (or after several hard freezes, when temperatures are consistently below freezing). Applying it too early can trap warmth, preventing dormancy and encouraging rot.
   • Material: Use a loose, breathable organic material like straw, shredded leaves, pine needles, or wood chips. Straw is often preferred because it doesn't compact easily. Avoid heavy, wet materials that can suffocate the plant.
   • Thickness: Apply a generous layer, about 6-12 inches deep, directly over the plant's crown and extending slightly beyond its drip line. The goal is to create a insulating blanket.
   • Why: This mulch layer acts like a blanket, keeping the soil temperature more consistent and preventing damaging freeze-thaw cycles that can cause the plant to "heave" out of the ground.
5. Water (If Dry): If your fall has been exceptionally dry, give the plants a good, deep watering before the ground freezes completely. This ensures the roots are adequately hydrated before dormancy. However, avoid overwatering, especially if drainage is an issue.
6. Avoid Over-Fertilizing in Fall: Do not fertilize your mums in late fall, as this can stimulate new, tender growth that will be easily damaged by frost. Stop fertilizing in late summer/early fall.
7. In Spring: Once the danger of hard frost has passed and new green shoots begin to emerge from the base of the plant, gradually pull back the thick layer of winter mulch. Remove about half of it first, then the rest a few days later. This allows the soil to warm up and prevents new shoots from rotting or being smothered.

By following these steps, your garden mums will be well-prepared to withstand winter's chill and burst forth with vibrant new growth when spring arrives.

What is the Best Way to Winterize Potted Chrysanthemums?

Winterizing potted chrysanthemums requires a different approach than those in the ground, as pots offer less insulation and expose roots to colder temperatures more quickly. Bringing them indoors or providing significant protection is essential for their survival.

Here are the best ways to winterize potted mums:

1. After Flowering and First Light Frost: Similar to garden mums, let your potted mums finish their blooming cycle. It's okay for them to experience a few light frosts; this signals them to go dormant. However, do not leave them out for hard freezes that would freeze the root ball solid.

2. Cut Back Foliage: Once the blooms have faded and the foliage starts to brown (typically late fall):

   • Using clean, sharp pruning shears, cut the stems back to about 4-6 inches from the soil line. This reduces the amount of plant material that needs to be supported over winter and minimizes the risk of pests or diseases overwintering.

3. Prepare the Pot:

   • Clean Up: Remove any dead leaves or debris from the soil surface to prevent fungal issues.
   • Water Well (If Dry): Give the pot a good, deep watering if the soil feels dry. You want the soil to be moist, but not soggy, before storage.

4. Choose Your Overwintering Location: This is the most crucial decision for potted mums.

   • Option 1: Unheated Garage, Shed, or Cold Cellar (Ideal for Dormancy)

     • Conditions: Look for a cool, dark, and consistently above-freezing location (ideally 35°F to 50°F or 2°C to 10°C). Good air circulation is a plus.
     • Process:
       1. Move the potted mum into this location before temperatures consistently drop below freezing.
       2. Place the pots close together to help retain warmth, or consider wrapping the pots in burlap or bubble wrap for extra insulation, especially if temperatures might fluctuate.
       3. Watering during dormancy: Water sparingly, only about once a month, just enough to prevent the soil from drying out completely and the roots from shriveling. The goal is to keep the plant dormant, not actively growing. A soil moisture meter can help gauge when to water.
     • Benefits: Mimics natural dormancy, high success rate.

   • Option 2: Burying the Pot in the Garden (For Zones 5-7, with Caution)

     • Conditions: Requires well-drained soil in a sheltered spot. Best for areas with moderate winters.
     • Process:
       1. Dig a hole in your garden bed large enough to fully accommodate the potted mum.
       2. Place the entire pot into the hole, ensuring the rim of the pot is level with or slightly below the surrounding soil.
       3. Fill in around the pot with soil, then apply a generous 6-12 inch layer of mulch (straw, shredded leaves) over the buried pot and surrounding soil, extending out beyond the pot's edges. This insulates both the pot and the surrounding ground.
     • Benefits: Provides insulation from the ground.
     • Considerations: Still more vulnerable than in-ground mums. Requires digging it up in spring. Ensure excellent drainage.

   • Option 3: Bringing Indoors as a Houseplant (Challenging, Not Ideal for Long-Term)

     • Conditions: Bright, cool room (around 60-65°F or 15-18°C) with high humidity.
     • Process: This is generally not recommended for true garden mums as they need a dormant period. Florist mums, however, sometimes attempt this. If you try, cut back dead foliage, provide bright light, and maintain consistent but not soggy moisture.
     • Benefits: You get to enjoy the plant indoors.
     • Considerations: Garden mums rarely thrive indoors long-term. They need a rest period. Pests like spider mites are common indoors.

5. In Spring:

   • Once the danger of hard frost has passed, gradually bring your potted mums out of storage.
   • Begin watering more regularly and move them to a brighter location.
   • Look for new green growth. When active growth resumes, you can move them to a sunny spot outdoors, gradually reintroducing them to the elements.
   • Consider repotting into fresh potting soil for flowers and possibly a slightly larger pot if the plant has become root-bound.

By choosing the most suitable overwintering method for your potted mums and executing it carefully, you can successfully preserve them for another vibrant blooming season.

What is the Difference Between Garden Mums and Florist Mums for Winterizing?

Understanding the difference between garden mums and florist mums is crucial for successful winterizing, as their cold hardiness and inherent growth habits vary significantly. While both belong to the Chrysanthemum genus, they are bred for different purposes, impacting their ability to survive winter.

Here's a breakdown of their key distinctions regarding winterization:

Why the Difference Matters for Winterizing:

• Genetic Hardiness: Garden mums have the genetic programming to survive cold temperatures. Their cells are better equipped to handle freezing and thawing cycles if their crowns are protected. Florist mums lack this inherent cold tolerance.
• Root Development: Garden mums develop a strong, extensive root system that helps anchor them and store energy through winter. Florist mums, often grown quickly in small pots, have a less robust root system, making them highly susceptible to damage from freezing soil.
• Dormancy Needs: Garden mums readily enter dormancy when outdoor temperatures drop, which is crucial for their survival. Florist mums, being bred for continuous bloom, often struggle to enter true dormancy, or they are forced into bloom at an unnatural time, leaving them unprepared for winter.
• PGRs (Plant Growth Regulators): Florist mums are often treated with PGRs to keep them compact for sale. These chemicals can inhibit their natural root development and overall vigor, further reducing their ability to overwinter successfully.

In summary, if you want your chrysanthemums to return year after year, invest in garden mums from a reputable nursery. These are the varieties designed for successful winterization. The beautiful florist mums are best enjoyed for their seasonal display and then composted, as their chances of overwintering are very slim.

Can Chrysanthemums Survive Winter Without Winterizing?

Chrysanthemums can survive winter without specific winterizing in very specific conditions, but for most gardeners, it's a risky gamble. Whether a mum survives without intervention largely depends on its type (garden vs. florist) and your local climate.

Here's when chrysanthemums might make it through winter on their own and why they often won't:

• When They Might Survive Without Specific Winterizing:

  • In Very Mild Climates (USDA Zones 8/9 and warmer): In regions where the ground rarely or never freezes solid, or where only light, brief frosts occur, hardy garden mums might naturally overwinter without a thick layer of mulch. The soil temperatures remain high enough that their shallow root systems are not significantly damaged.
  • With Natural Snow Cover: A consistent, deep blanket of snow acts as an excellent natural insulator. If your region reliably receives heavy snow early in winter that stays throughout the cold months, it can provide enough protection for garden mums, even in colder zones. However, relying on snow alone is unpredictable, as snow cover can be inconsistent.
  • In Well-Drained, Sheltered Locations: If garden mums are planted in exceptionally well-drained soil (to prevent crown rot) and in a very sheltered spot (e.g., against a warm foundation wall, protected from harsh winds), they might have a higher chance of survival without extra effort.
  • Very Established, Robust Plants: Older, well-established garden mum plants with extensive root systems sometimes have a better chance of surviving un-winterized than newly planted ones, as they have more stored energy.

• Why They Often Won't Survive Without Winterizing (Most Common Scenarios):

  • Cold Climates (USDA Zones 7 and colder): In these zones, ground temperatures consistently drop well below freezing. Without insulation, the shallow roots of garden mums will freeze solid, leading to cell damage and death.
  • Fluctuating Temperatures & Frost Heave: This is a major killer. If your region experiences repeated cycles of freezing temperatures followed by thaws, the soil expands and contracts. This "frost heave" can literally push the mum's crown and roots out of the ground, exposing them to lethal cold and drying winds. Mulch prevents this.
  • Wet Winter Conditions: While freezing is the primary concern, excessive moisture combined with cold temperatures can lead to crown rot in mums. Without good drainage or some protection, the plant can succumb to fungal diseases before spring.
  • Florist Mums: As previously discussed, florist mums are not bred for cold hardiness. They are highly unlikely to survive outdoors in any but the most exceptionally mild, frost-free climates without significant intervention to bring them indoors.
  • Newly Planted Mums: Mums planted in the fall, especially late in the season, haven't had enough time to establish a robust root system before winter sets in. These are far more vulnerable and almost certainly require winterization to survive.

In conclusion, while a fluke of mild weather or consistent deep snow might allow an un-winterized garden mum to survive, relying on this is not a sound strategy for ensuring their return. For consistent success and to protect your investment, taking the few simple steps to winterize chrysanthemums is highly recommended in most climates.

What is the Purpose of Mulch in Winterizing Mums?

The purpose of mulch in winterizing chrysanthemums is primarily to act as an insulating blanket, protecting the plant's shallow root system and crown from the damaging effects of winter. It's not about keeping the plant warm, but rather about keeping the soil temperature stable.

Here are the key roles of mulch in winterizing mums:

• Temperature Stabilization (Insulation):
  • Prevents Extreme Cold: Mulch reduces the depth to which frost penetrates the soil, preventing the mum's roots from freezing solid, which would rupture their cells and kill the plant.
  • Reduces Temperature Fluctuations: This is perhaps its most crucial role. Instead of the soil rapidly freezing and thawing during winter mild spells and cold snaps, the mulch layer keeps the soil temperature more consistent.
• Prevents Frost Heave:
  • When soil repeatedly freezes and thaws, it expands and contracts. This can physically push shallow-rooted plants like mums out of the ground, exposing their crowns and upper roots to lethal cold air and drying winds.
  • Mulch moderates the soil temperature swings, preventing or significantly reducing this damaging "heaving" action, keeping the plant securely anchored in the soil.
• Moisture Regulation:
  • Retains Moisture (if dry): A good layer of mulch can help retain some soil moisture, which is important if your fall has been unusually dry, ensuring the roots don't dry out completely.
  • Protects from Excessive Wetness (if well-drained): While it retains some moisture, a loose, breathable mulch (like straw) also allows excess water to drain away, preventing waterlogging around the crown that can lead to rot in overly wet winter conditions.
• Protection from Drying Winds: Winter winds can be incredibly harsh and desiccating, especially in colder climates. Mulch creates a barrier that protects the plant's crown from drying out.
• Weed Suppression (Secondary Benefit): While not its primary purpose in winter, a thick layer of mulch will also help suppress early spring weeds around your mums, giving them less competition when they emerge.

Important Mulch Considerations:

• Timing: Apply mulch after the ground has frozen solid or after several hard freezes, when the plant is fully dormant. Applying it too early can trap warmth and moisture, potentially preventing dormancy or encouraging rot and pests.
• Material: Use a loose, breathable organic material like straw, shredded leaves, pine needles, or well-shredded bark. Avoid heavy, compacting materials that can smother the plant or retain too much moisture, leading to rot. Straw is an excellent choice as it provides good insulation and doesn't compact easily.
• Thickness: A substantial layer of 6-12 inches is recommended over the plant's crown and root zone.

By understanding the vital role of mulch, you can effectively use it as your primary tool to winterize chrysanthemums and ensure their healthy return year after year.