How to Overwinter Dahlias: Dig, Store & Replant Next Spring
Dahlias are some of the most rewarding flowers you can grow, producing everything from dinner-plate blooms to delicate pompons in shades of pink, red, yellow, orange, purple, white, and nearly every combination in between.
But when autumn arrives and frost threatens, many gardeners face an important question:
What should you do with the dahlia tubers?
In cold climates, leaving dahlias in frozen or waterlogged soil can result in significant losses. The good news is that you don't have to buy new plants every spring. You can dig up the tubers, dry them, store them in a cool frost-free location, and replant them when spring returns.
Dahlias are tender perennials rather than reliably winter-hardy plants. Their underground tubers store energy that allows the plant to regrow when conditions become favorable again.
The process sounds complicated at first, but once you understand the timing and storage conditions, overwintering dahlias becomes a straightforward part of the gardening calendar.
When Should You Dig Up Dahlia Tubers?
The ideal timing depends on your climate.
A common approach is to wait until the first frost damages the foliage but dig the tubers before a hard freeze reaches the ground.
The RHS recommends lifting dahlias once the foliage has been damaged by the first frosts, while Penn State Extension notes that gardeners don't necessarily have to wait for frost if the tubers have had enough time to mature.
If your growing season is long and frost arrives late, you can often enjoy the flowers for longer before lifting.
If a severe freeze is approaching, don't wait simply to squeeze out another few days of flowers.
A simple rule:
Enjoy the blooms as long as conditions allow, but lift the tubers before a hard freeze can damage them.
Dahlias need time in the ground to develop mature tubers. Penn State Extension notes that plants need at least about 120 days in the ground to produce mature tubers suitable for storage.
Step 1: Let the Plant Finish Growing
Before digging, allow the dahlia to complete as much of its natural growing cycle as possible.
The leaves use sunlight to produce energy that is stored in the underground tubers.
If you dig too early, the tubers may be smaller and less mature.
This is particularly important if you planted dahlias relatively late in the season.
Watch the weather forecast as autumn progresses.
When frost begins damaging the upper growth, the plant is giving you a useful signal that the season is coming to an end.
Step 2: Cut Back the Stems
Once the foliage has been damaged by frost—or when you're ready to lift the plant before severe weather—cut the stems back.
Leave a manageable section of stem above the tuber clump so you can handle the plant easily.
The RHS recommends cutting stems back to roughly 2–6 inches (5–15 cm) for stored tubers.
Penn State's recent guidance also recommends cutting the stalk down before lifting the clump.
Don't worry about making the cut perfectly precise.
The purpose is simply to remove most of the top growth and make the underground clump easier to handle.
Step 3: Dig Carefully
This is one of the most important parts of the entire process.
Dahlia tubers are surprisingly easy to damage with a shovel or fork.
Instead of digging directly beside the crown, start several inches away from the plant.
Use a garden fork or spade to loosen the soil around the entire clump.
Work gradually around the plant rather than forcing the tool underneath from one side.
The University of Minnesota Extension specifically recommends loosening the soil several inches away from tender bulbs and taking care not to cut or bruise the fleshy underground structures.
Once the soil is loose, gently lift the clump.
Avoid these mistakes:
- Don't stab directly through the crown.
- Don't yank hard on the remaining stems.
- Don't throw the tubers onto a hard surface.
- Don't scrape away their skin aggressively.
Cuts and bruises can create entry points for rot.
Step 4: Clean the Tubers
Once you've lifted the clump, remove loose soil so you can inspect the tubers.
There are different approaches to cleaning.
Some gardeners leave much of the soil attached, while others gently wash the clumps.
The RHS recommends shaking off as much soil as possible and storing only healthy, dry, undamaged tubers. The University of Minnesota Extension says dahlias can be washed gently with a hose before curing.
If you wash your tubers, avoid using excessive pressure.
You want to remove soil without damaging the outer skin.
After cleaning, inspect every section carefully.
Look for:
- Soft spots
- Black or brown rotten areas
- Broken sections
- Mold
- Severe damage
- Very thin or shriveled tubers
Don't put obviously rotten material into storage with healthy tubers.
Step 5: Let the Tubers Dry
Drying is one of the most important steps because excess moisture can encourage rot.
Place the cleaned tubers somewhere protected from direct sunlight with good air circulation.
Allow them to dry before long-term storage.
The University of Minnesota Extension recommends curing dahlias for approximately 1–3 days, depending on temperature and conditions.
The RHS recommends drying the tubers thoroughly and turning them upside down for a period so moisture can drain from the hollow stems.
Don't place freshly washed tubers immediately into a sealed container.
They need time for surface moisture to evaporate.
Step 6: Decide Whether to Divide the Tubers
You don't necessarily need to divide dahlia clumps before winter.
In fact, keeping a clump intact can simplify the storage process.
If you want to create more plants, however, you can divide the clump.
The important thing is that each division needs a viable eye attached to the tuber section.
An eye is a small growth point from which a new shoot can emerge.
Penn State Extension explains that a viable tuber needs a neck and crown with an eye, while the RHS notes that each divided piece needs a green bud at the top to produce a new plant.
If you're new to dividing dahlias, consider waiting until spring.
The RHS recommends dividing stored clumps in spring because wounds made before winter storage can provide entry points for rot.
Step 7: Label Every Dahlia
This small step can save you a lot of confusion next spring.
If you grow several dahlia varieties, label them before storage.
Record:
- Cultivar name
- Flower color
- Flower type
- Approximate height
- Where it grew in the garden
You can use waterproof plant labels or another durable identification system.
Penn State Extension recommends carefully labeling stored tubers so varieties aren't mixed up.
This becomes especially valuable when you have multiple varieties that look similar as dormant tubers.
Step 8: Choose the Right Storage Location
The storage location can make or break your overwintering effort.
Dahlia tubers need protection from freezing temperatures, but they shouldn't be stored in a warm, wet environment either.
The University of Minnesota Extension recommends cool, dry storage for tender bulbs, while Penn State guidance gives approximately 45–55°F (7–13°C) as a suitable range for many tender plants stored dormant.
The RHS recommends a dark, cool, frost-free storage location.
Good possibilities may include:
- An attached garage
- A cool basement
- A frost-free shed
- An unheated but protected storage area
- Another cool location that remains above freezing
Avoid areas that routinely freeze.
Also avoid very warm rooms where tubers may lose moisture too quickly or begin growing prematurely.
Step 9: Choose a Storage Medium
Dahlia tubers can be stored using different materials.
Common options include:
- Dry potting compost
- Vermiculite
- Sand
- Peat-free growing material
- Wood shavings
The purpose is to create a stable environment that protects the tubers without keeping them excessively wet.
The RHS recommends covering tubers in shallow crates or open-topped boxes with insulating material such as dry spent potting compost, sand, straw, or newspaper.
Penn State's recent storage guidance describes using cedar shavings in ventilated containers and emphasizes adjusting the setup if the medium becomes too moist.
There's no single storage material that works perfectly in every home.
Your local humidity, temperature, container, and tuber condition all matter.
Step 10: Don't Seal the Tubers in an Airtight Container
Air circulation matters.
A completely sealed container can trap moisture and create conditions favorable for rot.
If you use a plastic storage container, make sure the setup provides appropriate ventilation.
Penn State's recent guidance uses plastic bins with ventilation holes and does not seal the lids completely.
A breathable or ventilated storage system gives you more control over moisture.
The goal isn't to make the tubers bone-dry.
It's to prevent both extremes:
Too wet = rot.
Too dry = shriveling.
Step 11: Check the Tubers During Winter
Don't put your dahlias into storage in October and forget about them until April.
Check them periodically.
Look for:
- Soft spots
- Mold
- Rot
- Excessive shriveling
- Premature shoots
- Unusual odors
The University of Minnesota Extension recommends periodically checking stored tender bulbs and removing damaged or rotting material.
If one tuber begins rotting, remove it promptly so the problem doesn't spread to healthy material.
If everything looks healthy, close the storage area back up and leave the tubers undisturbed.
What If Dahlia Tubers Start Shriveling?
Some slight moisture loss is normal.
But if tubers become severely wrinkled, soft, or extremely dry, the storage conditions may need adjustment.
Penn State notes that storage humidity affects tuber condition and that a slightly dry medium may sometimes require a small amount of added moisture.
Don't soak the tubers.
The goal is controlled moisture, not wet storage.
A tiny adjustment is very different from pouring water into the storage container.
What If Dahlia Tubers Start Rotting?
Remove affected material immediately.
If only part of a tuber is affected, you may be able to cut away the rotten section with a clean tool until healthy tissue remains, depending on the extent of damage.
The University of Minnesota Extension advises removing rotting material and, in some cases, cutting dahlia tissue back to clean, healthy flesh.
If an entire tuber is badly rotten, discard it rather than risking the healthy collection.
The best cure for storage rot is prevention:
Start with healthy tubers, avoid bruising them, dry them properly, and maintain appropriate storage conditions.
Can You Leave Dahlias in the Ground Over Winter?
Sometimes—but it depends heavily on climate and soil.
Dahlias are tender, so leaving them outdoors through winter is risky in areas with hard freezes.
The RHS notes that dahlias may survive outdoors in milder regions, particularly in light, free-draining soils, but heavy winter rain and severe cold increase the risk of losing tubers.
If you live somewhere with mild winters and excellent drainage, outdoor overwintering may be possible.
If your winters regularly produce hard freezes, lifting the tubers is the safer strategy.
The biggest outdoor risks are:
- Deep freezing
- Waterlogged soil
- Repeated freeze-thaw cycles
- Poor drainage
- Severe winter temperatures
If you decide to leave dahlias in the ground, substantial insulating mulch can help in suitable climates, but it does not eliminate the risk.
When Should You Replant Dahlia Tubers in Spring?
Don't rush.
Dahlia tubers are sensitive to frost.
They should be planted outdoors after the danger of hard frost has passed and the soil is suitable for growth.
The RHS recommends keeping stored tubers protected from frost and planting them outdoors once frost danger has passed; stored tubers can also be started indoors earlier for a head start.
Your local last-frost date is a useful starting point.
If you're uncertain, it's better to wait slightly longer than to expose newly emerging shoots to a damaging freeze.
Step 12: Wake Up the Tubers in Spring
If you want earlier flowers, you can start your dahlias indoors several weeks before the outdoor planting window.
Place tubers in containers filled with a suitable, well-draining growing medium.
Keep them in a warm, bright, frost-free location.
Water carefully.
The RHS warns that overwatering dormant or newly planted tubers can quickly cause rot, so keep the medium only slightly moist as shoots begin developing.
Once outdoor conditions become safe, gradually acclimate the plants before moving them permanently outside.
This process is called hardening off.
Step 13: Replant Dahlias in a Sunny Location
Choose a location with plenty of sunlight and fertile, well-drained soil.
Dahlias perform best in warm, sunny conditions.
The RHS recommends a warm, sheltered, sunny location with fertile soil that remains moist but drains freely.
When planting dormant tubers, position them correctly.
The crown and eyes should be oriented upward.
Cover them according to the planting instructions for your variety and local conditions.
Avoid planting too deeply.
As the shoots emerge, protect young growth from slugs, snails, and late frosts.
How to Get More Flowers From Overwintered Dahlias
Overwintering successfully is only half the process.
Once your dahlias return to active growth, good seasonal care can help create a spectacular display.
Give Them Plenty of Sun
Dahlias need strong light for vigorous growth and flowering.
Water During Dry Weather
They are thirsty plants, particularly when growing actively.
Feed Appropriately
The RHS recommends potassium-rich liquid fertilizer for container dahlias during the flowering season.
Deadhead Regularly
Removing spent flowers encourages continued flowering.
The RHS recommends deadheading dahlias regularly, ideally weekly, during the flowering season.
Support Tall Varieties
Large dahlias can become top-heavy, especially when wet.
Install supports before plants become difficult to manage.
5 Common Dahlia Overwintering Mistakes
1. Digging Too Early
Tubers need sufficient time in the ground to mature.
2. Damaging the Tubers While Digging
Cuts and bruises can encourage rot.
3. Storing Them Wet
Excess moisture is one of the biggest threats during storage.
4. Letting Them Freeze
A frost-free storage area is essential.
5. Forgetting to Check Them
A single rotting tuber can become a problem if ignored for months.
Avoiding these mistakes can dramatically simplify the process.
Dahlia Overwintering Checklist
Before storing your dahlias, make sure you've completed these steps:
- Wait until tubers are mature.
- Watch the weather.
- Cut back the stems.
- Loosen the soil carefully.
- Lift the clump without bruising it.
- Clean away excess soil.
- Inspect for damage and rot.
- Allow the tubers to dry.
- Label each variety.
- Divide only if appropriate.
- Place them in a cool, frost-free location.
- Provide suitable ventilation.
- Check them periodically.
- Remove rotten material promptly.
- Replant after frost danger has passed.
Save this checklist and use it every autumn.
Frequently Asked Questions
Do you have to dig up dahlias every year?
In cold climates, digging and storing dahlia tubers is generally the safest way to protect them from freezing temperatures. In milder climates with well-drained soil, some gardeners successfully leave them in the ground, but winter losses remain possible.
When should I dig up dahlia tubers?
A common approach is to lift them after the first frost damages the foliage but before a hard freeze reaches the soil. In areas where frost arrives late, tubers can sometimes be lifted before frost once they've had sufficient time to mature.
How do you store dahlia tubers over winter?
Clean and dry healthy tubers, then store them in a cool, dark, frost-free location using an appropriate dry or lightly insulating medium and adequate ventilation. Check them periodically for rot or excessive shriveling.
What temperature is best for storing dahlia tubers?
A cool, frost-free environment is ideal. Penn State guidance gives approximately 45–55°F (7–13°C) for many tender plants stored dormant, while the RHS recommends a cool, dark, frost-free location.
Should dahlia tubers be washed before storage?
They can be gently washed, although some gardeners prefer leaving soil around intact clumps. If you wash them, allow them to dry thoroughly before storage.
How long should dahlia tubers dry before storage?
The curing period varies with conditions. The University of Minnesota Extension recommends roughly 1–3 days for dahlias, while other successful storage systems may use longer drying periods depending on humidity and the condition of the tubers.
Can you leave dahlias in pots over winter?
If container-grown dahlias are moved into a cool, frost-free location, the entire container can sometimes be overwintered. Penn State Extension notes that container-grown tender plants can be cut back and stored in suitable cool, dark conditions.
Should I divide dahlia tubers before storing them?
You don't have to. Keeping a clump intact can simplify storage. If you want to divide, make sure every section has a viable eye. The RHS suggests dividing in spring because cuts made before storage can increase the opportunity for rot.
Why are my stored dahlia tubers rotting?
Rot can result from damaged tubers, excessive moisture, poor ventilation, or unsuitable storage temperatures. Inspect stored tubers regularly and remove rotten material promptly.
When can I plant overwintered dahlias outside?
Plant them outdoors after the danger of damaging frost has passed and soil conditions are suitable. You can also start stored tubers indoors earlier and transplant them after hardening off.
Final Thoughts
Overwintering dahlias may seem like a lot of work the first time, but once you have a reliable routine, it becomes one of those satisfying seasonal gardening jobs that pays you back the following year.
The basic process is simple:
Dig carefully. Clean and dry the tubers. Store them cool and frost-free. Check them during winter. Replant after frost danger has passed.
The most important thing is to protect the tubers from the two biggest threats: freezing and excessive moisture.
If you live in a cold climate, lifting and storing your dahlias is generally the safer option. If you garden in a mild region with excellent drainage, leaving some tubers in the ground may be possible, but it carries more winter risk.
And when spring finally arrives, those seemingly lifeless tubers can come back to life with new shoots and another season of spectacular flowers.
A little autumn effort can mean years of beautiful dahlias from the same treasured tubers.
