So, you want to overwinter your dahlia for the coming winter.
Did you know they can be stored and saved for next year?
Did you know dahlia are perennials and come back every year?
Sadly, a lot of people don’t. They toss them.
But that’s not gonna be you, because you’re going to learn how to winterize dahlia bulbs!
So let’s get started.
Last updated: 11/10/21.
Quick care guide: Dahlia
|Scientific name||Dahlia pinnata|
|Sunlight requirement||Full sun|
|Bloom season||Summer, fall|
|Colors||Orange, white, pink, green, blue, red, yellow, lavender, peach, bi-color|
|Max height||5 feet|
|Max width||2 feet|
|Watering requirements||Deep watering twice a week|
|Fertilizer requirements||Every 3-4 weeks (5-10-10 or 10-20-20)|
|Days until germination||7-12 days|
|Days until bloom||8 weeks|
|Speed of growth||Slow|
|Hardiness zones||8-11 (winter hardy), 3-7 (annuals only)|
|Plant depth||6-8 inches|
|Plant spacing||12-18 inches|
|Propagation||Seeds, tubers, or cuttings|
|Common pests||Aphids, thrips, mites, leafhoppers, slugs, snails, spiders, caterpillars.|
|Common diseases||Fungus, rot, mold, mildew.|
|Uses||Decoration, color, centerpiece, cosmetics, dye, ornamental, medicinal, food.|
Wintering and storing dahlia: Things to know
These plants are not cold hardy and will require the tubers to be lifted, cleaned, dried, and stored for the winter (overwintering).
Dahlia plants are perennials and are hardy in zones 8-11. They’re susceptible to cold temperatures that dip below 40F.
So most people need to take them inside- unless you’re somewhere with mild winters.
But even then, cold snaps and humid temps may contribute to root rot and fungus- and powdery mildew. The plants will also start to blossom fewer times each year you don’t dig up the bulbs and help it propagate.
So don’t get lazy if you want to get the most out of your dahlia.
How to winterize dahlia
Here’s how to winterize your dahlia. It all starts with the right prep, followed by cleaning and storing.
The process is very easy even if you’ve never done it before.
And we’ll cover it step-by-step in this guide.
When to lift dahlia bulbs for winterizing
Dahlia can be lifted and prepped for wintertime storage just like any other bulb plant (such as caladiums), but you’ll want to wait as late as possible for these delicate bulbs.
Dahlia can be raised in zones 3-7, but only as an annual because they’ll be killed by the winter frost (unless extreme overwintering measures are done).
Zones 8-11 are perfect for this flowering ornamental and the least amount of work will be needed. Some people may even be able to leave them outside during the cold if the winters are mild. Basic plant covers, mulch, and wraps should do the trick.
Even then, you should avoid this because it’ll result in weaker blooms. Lifting and dividing the bulb is the best way to go for the best blooms.
They begin bulb development during the springtime and often continue to develop until late spring or early fall. Thus, if you intervene and disrupt it, it could cause plant harm, smaller blooms, or even failed blossoms.
So give your dahlias as much time as they need to bloom and develop their tubers. Don’t panic.
The longer you wait, the more developed and harder they become for the winter. You’ll have plenty of time to dig them out later.
You’re doing them a favor by doing nothing. This will result in a hardier, more robust bulb that’ll have a higher chance of doing well over the colder seasons.
Acclimate the bulbs to cold weather
When the temperatures drop and the winter is upon us, this is when you’ll want to pay extra attention to the weather.
The trick is to let the cold arrive, but keep the temperatures above freezing.
Typically, winter doesn’t come all at the same time. You don’t just wake up the next day into a hard freeze.
You’ll get a few light frosts before the first “real” hard freeze. Let the bulbs stay outside during the first few touches of the frost of winter.
This will help them acclimate to the temperature and also enter dormancy properly. There’s no need to shield them from these frosts unless you’re getting freezing temperatures.
Allow the bulbs to weather through one or two touches of frost. THEN go ahead and dig them up.
This is a balancing act and will require you to watch the weather in your forecast. If the first frost is hard, then dig them up without giving it a chance (after doing the following steps).
The hard frost will kill your dahlia bulbs. But a light frost is good for them.
As you acclimate your dahlia, the foliage will die back- sometimes completely. Don’t panic. This is normal.
The frost will force your flowers to wilt and all the foliage to drop off.
The only remnants that should be left are the tubers before you dig it up. If there’s any leaves leftover and it’s time to lift the bulb, go ahead and deadhead it.
So, winter’s officially here. You gave your dahlia a few touches of frost. The leaves dropped off.
Now it’s time to cut your plant back before we dig it up. Get a clean pair of shears and cut the remaining foliage off- including the stems.
Some people will leave the stems on, and that’s okay.
But I prefer to cut them off because they easily capture water. This can rot your dahlia because they don’t appreciate excuses moisture.
You can cut the stems off down to the crown.
However, if you cut them off and decide not to lift your tubers, you need to cover them at the ends you cut since they’re hollow. This allows pests and water to seep in and get to the crown.
You can cover it with a piece of food wrap, foil, or parchment paper with a twist tie. That should be able to protect the exposed end of the hollow dahlia stem.
So only cut the stems down to the crown when you’re ready to dig up the bulb. Otherwise, don’t cut them off.
You can do a “pre-cut” by trimming them down to a few inches before you do the final trim.
Cut back about a week before you dig out the bulb. This won’t be enough time for major plant infections to form or any rapid pest damage.
It’s only if you cut them way early that it becomes a problem. Doing this early cut will help make it easy to see where the eyes are for next season’s sprout.
Once you cut them down completely, it’s difficult to tell the bulbs apart from one another if you have different cultivars of dahlia. Add a market stake to separate them.
How to lift the bulbs
And now, the exciting part.
These plants are extremely fragile, so you’ll want to take every precaution you possibly can so you don’t end up chopping the crown from the tuber.
Use a garden spade or small shovel and start by digging around the tuber. You’re just loosening the soil and forming a moat so there’s space for the excess soil to go.
You should start early in the day because this process takes a few hours.
Dig out a small perimeter around the bulbs. Inch slowly towards them.
Once you get close enough, switch to a smaller tool, and continue digging.
Remove excess soil by hand. Reach under the bulb and lift to remove it completely. The tubers usually extend down to 8” under the soil.
So dig to at least 8” then start to loose then compact soil. You should be lifting from the sides only. Never pull from the top or above.
Use your fingers to get rid of any stuck clumps. Do NOT use a tool to do this.
You can break the necks of the bulb easily because they’re extremely brittle at this point. You can also use a pressurized garden hose at a minimal setting.
This will spray off and remove any dirt that’s stuck. This will clean up your bulb at least 3/4 of the way. The remaining dirt that you can’t get off is fine. We’ll clean it later indoors.
After you’ve dug up all the tubers, leave them on the soil surface for a few hours until early dawn. This will prep them even further.
When nighttime comes, you can take them indoors and start cleaning them up.
Handle them with care because the crowns can snap off the tuber and break it in half. This will make it hard (read: impossible) to propagate later on if you decide to.
The necks are easy to break if handled incorrectly, so you should only transport them as carefully as you can.
Sorting the bulbs
Place them under a bright light. It’s time to do some sorting.
The point of this step is to get rid of the weak or damaged dahlias and only keep the best ones. If it’s your first harvest, you may be inclined to keep them all.
And that’s fine. But if you want to maximize your work: reward ratio and get the best-looking dahlias with that hardiest nature, then you’ll want to sort them.
You can also just use a knife to cut away parts that are molding, rotting, or soft. This can save the tuber from disposal. It may be able to repair itself from the damage.
Spend some time doing this.
By removing any damaged or funny colored areas, you may save your dahlia bulbs from an outbreak of mold when they’re in storage over the winter.
You’ll want to prune off any excess foliage, soft skin, or simply toss out bulbs that don’t look the best.
This will help ensure a bountiful harvest of flowers next season by thinning out the weaker tubers. As usual, keep moisture to a minimum and don’t use water if you don’t have to.
Use clean shears or scissors to prune. Cleaning them will help prevent any root rot or other damages from fungus or other plant problems.
There’s no right way to do it- clean your dahlias however you want. If you get them wet, let them dry out completely before storing them.
Never put moist dahlia bulbs into storage. This will rot them up.
The next step is to cure or dry them out.
You should have a clump with a bunch of tubers and crowns sticking out it. It may look like a mess, but that’s okay.
Take the entire thing and put it upside down on a plate or lid.
Use something that collects water. Leave it there for at least 2-3 days or so. They will drain any excess water from the cluster to help reduce the chance of mold or root rot.
You want your dahlia to be 100% dry before you store them.
Even small amounts of moisture and contribute to bacterial breakouts, fungus, mold, or plant mildew. Rot is also common with these types of plants.
All of these can be controlled by eliminating the water from the tubers.
You’ll know when curing is complete because there will be no water on the plate. You can rotate it a few times during the curing process, but just be careful not to break it.
When the outer layer of skin on the bulb starts to feel leathery and visibly wrinkly, the drying step is complete!
How to store dahlia tubers for winter
And lastly, we get to the actual storage.
Storing dahlia tubers over the winter is easy and straightforward.
The key here is to expose them to winter chill so they enter dormancy, but not overdo it so they freeze.
The other thing to keep in mind is to make it as clean and sterile as possible.
This will eliminate the possibility of mold and rot- both of these are more dangerous than any cold snaps overnight.
What to use to store the bulbs
There are multiple materials you can use to store dahlia.
Some of the most popular choices are:
- Plastic bins
- Paper bags
- Storage containers
- Plastic wrap
I suggest avoiding any paper-based products because these will mold when wet.
Storing your dahlia in cardboard or paper is just risking it. It’s unnecessary and plastic will do just fine. Mold will form when humidity is present.
And if your storage area is cold and damp, the excess moisture will gather on the paper-based products.
However, even plastic may lead to plant mildew or root rot. Plastic doesn’t allow air exchange and traps moisture just like paper absorbs it.
So there’s no “perfect” way to store dahlia bulbs. It’s all about eliminating moisture and keeping air circulating as much as possible.
Some people use a fan or air circulator in rooms that they store plants. This can work but will require you to invest in running a fan all winter long.
Choosing a substrate for storage
After you select a storage container, the next step is to choose a substrate.
The key here is to use something that’s light and not compact so the moisture can escape. It should also separate the plants from one another. This can help stop the rot from ruining your entire set.
So don’t skimp on this. Get high quality, organic, or natural substrate.
Any of these are excellent choices:
- Coconut coir
- Peat moss
- Light soil
You can also make your own blend if you’re experienced. Whatever works for you.
Packing the dahlias
First, get your storage container and put a thick layer of newspaper or magazine at the bottom.
Use about 3” of packing medium so it’s nice and cushy against the container.
This will help absorb some moisture that seeps and keeps it higher up to avoid cold.
Then place the bulbs into the newspaper, one at a time.
Space them evenly so they’re not touching each other. Make sure they’re fully dry.
And cut off any foliage or roots that may have grown during the curing earlier.
Add more of your substrate to separate all the bulbs from each other until they’re completely covered.
Add another layer of newspaper at the surface and you’re all set!
Hopefully, your container has a lid (such as those plastic storage bins). If not, you can make one or just use something to keep humidity out.
Some gardeners will add a plant fungicide to kill any possible fungi from infecting the plant during storage.
You can buy a bottle if you please and apply as directed. A light dusting of it on the bulb should do the trick.
Where to store dahlia
Pick an area that’s cold enough where the temperatures drop down to 45F on average.
This will offer the chill hours dahlia need during the wintertime for proper dormancy.
Place the container somewhere cold and dark.
Some popular places are the cellar, basement, shed, garage, or even attic. There’s no need to get fancy.
Just get a basic thermometer and humidity gauge to make sure the temperature and moisture are good. That’s it.
Check on it often
After it’s stored, don’t just forget about them.
Check on them once a month or so to look for rotting or damaged bulbs.
Discard them right away and continue to monitor problematic ones. Make sure the temps and the humidity are within range.
When you should bring them out of storage
When the cold has ended, it’s time to bring your dahlias back!
The first step is to put the container somewhere warm so they can slowly acclimate to springtime. They’ve been indoors for many days so they have no idea when it’s time for spring.
Place the dahlia bulbs in an area with a temperature of 65F and keep it dark. This should be after the last frost, which should be right around late winter or the coming of spring.
Start to water your bulbs also.
Use a few spritzes of water on the substrate every week. Continue doing this until you’re ready to transplant them outside.
Over time, the excess humidity and raised temps will signal that spring is here and it’s time to blossom once again.
it’s time to bring them back outside.
Start by slowly picking up each bulb from the substrate and shaking off any dirt or substrate stuck to them.
They should look dry and clean. If you see any rot, dispose of those bulbs.
Check for soft, moldy, or weak tubers and get rid of them.
The ones that are damaged or have soft crowns or necks should also be disposed of.
Don’t try to save them because you just may end up rotting the other bulbs also- unless you’re into freaky experiments or something like that.
Use a clean pair of garden shears and start cutting single slices of the bulb ends.
You only need a thin slice to see the inside of it and assess the status. If you see any rot, mold, or weird colors, throw it out. If there’s any roots or stems present, cut those off also.
The more old foliage you remove, the healthier the plant can start with new energy.
You should be able to see the new eyes somewhere on the bulb.
Cut directly along the bunch leaving a piece of the crown on each tuber. If all of them have a small crown piece attached to the bulb with a strong neck, it should propagate nicely.
You can cut it into many different pieces for plenty of dahlias.
Use a sharp pair of scissors and make sure it’s been sterilized first.
When cutting, be extra careful about snapping the necks of the crowns. These are brittle from that wintertime storage and will break easily under their weight.
So cut cleanly and give it plenty of support from the underside of the plant.
For each new clump, you divide, be sure to clean the scissors so you don’t end up giving all of them a fungal infection or rot.
You can use rubbing alcohol, or diluted bleach to do the trick.
Lastly, to be extra safe, apply some fungus killer to each of the newly cut areas that are exposed.
Just powder each section carefully according to the package directions.
This is what you do with dahlia tubers in spring.
Plant your dahlia
After that, go ahead and plant!
Keep the bulbs wet and give them plenty of sunlight.
Soon enough, you’ll see your gorgeous, colorful dahlias back prettier than ever.
There should be no more risk of frost at this point. The last frost date should be over already.
Other FAQs about dahlia
Here are some other common questions people ask about these gorgeous flowering plants.
Do they need to be soaked?
Dahlia don’t need to be soaked when you’re cleaning the bulb.
Just use a light brush and clean off the debris stuck to the bulb or spray it with a garden hose.
If you’re referring to soaking them before planting, there’s also no reason to soak them.
They can go right into the soil and watered after they’ve been properly acclimated to the springtime weather.
No reason to make the process complicated, right? It should be easy!
Can you leave dahlias in the ground over winter?
If you live in a temperate area with cold seasons that aren’t that cold, then you can get away with it.
This is usually only zone 7 that has this privilege.
But even then, you’ll want to watch and check the weather report weekly so make sure there are no cold snaps. If there are, you need to do something about it- you can wrap, cover, mulch, etc.
Can you store dahlia in the fridge?
While this may seem like a good idea because the fridge is temperature-controlled, dark, and never has any cold snaps, the fridge traps moisture.
Any humidity is bad because it can lead to rot.
So this is why I suggest to NOT store them in the fridge, even if it makes it easy. The trapped moisture could seep into the newspaper then the substrate. This is dangerous.
Unless you can control the humidity and keep it low, then don’t put them in the refrigerator.
Can you leave them in pots over winter?
This completely depends on your hardiness zone.
If you’re in a zone that has warmer winters (zone 7), you can leave them outside during the winter.
They should be okay if the ambient temperature doesn’t drop below 40F for extended periods. The soil should be well-drained and they’ll probably need some outside insulation.
There are many things you can do to protect and winterize your dahlia outside.
You can do the following to keep your bulbs warm:
- Wrap the plant in burlap after deadheading it
- Use row covers
- Add newspaper or other soft material around it
- Add mulch to the soil
But if you’re someone colder or in zones 8+, you’ll want to bring them indoors following this guide.
Dahlia will suffer and droop at the first sign of frost.
What temperature is too cold for dahlias?
Dahlia bulbs are not cold hardy and will require temperatures above 40F during the winter.
They need chill hours for the proper dormancy, but can’t tolerate a cold snap. That’s why they’re brought indoors for storage- where the temperatures are stable and consistent.
Propagating dahlia from bulb
If you plan to replant new dahlias from the bulbs you harvested last season, the process is straightforward like any other tuber plant.
But there are some things you should keep in mind for successful propagation.
When you harvest the bulb from the soil, you need to make sure that you harvest it as a whole.
That means you DON’T leave any parts behind.
The bulb consists of a crown, tuber (commonly referred to as the bulb), and a connecting “neck” between the two pieces. If you have crowns that have missing pieces, bulbs, or necks, this won’t propagate.
The same goes for the bulb- it needs a crown connected to it for it to propagate properly.
So if you harvested incorrectly, you can get it right next season.
Don’t waste your time trying to plant bulbs that are missing parts. This will just result in a waste of energy and time.
Other than that, it’s just a matter of putting the bulb in the right depth and covering it lightly with soil.
Add some TLC and you’re set. Refer to the care guide above for more details.
Dahlia can also be divided by cuttings or straight from the harvested seeds.
Here are some additional references you may find useful:
Did you get your dahlia ready for the winter?
You should now know how to winterize and store them for overwintering to ensure a safe cold season.
Dahlias are perennials that are easy to grow and offer a gorgeous display of flowering blooms every summer.
They’re pretty foliage for any garden and can also make a nice piece for the table. They can even grow in a vase if you want to bring them to work!
No more buying plants over and over.
You can now give these gorgeous perennials a home every single year and they’ll be happy to show off for you.
What did you think? Were you able to go through the steps smoothly? Do you have any advice to give to other readers?
Leave a comment and let us know!
I took interest into microflora and microgreens before it became mainstream. The idea of growing an entire ecosystem on a tiny scale simply was astounding. That’s where I discovered that I actually like raising plants and wasn’t as much of a black thumb as I thought. Now, I’m relaying what I’ve learned to others who are getting into the hobby in a way that anyone can understand.