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As fall rolls in, it’s time for many of us to start digging up our dahlia tubers. Why? Because if they’re left in the ground in colder climates where the soil freezes, your tubers will turn to mush. If you’re in a warmer region, you might be lucky enough to leave them in the ground all year. But for those of us in areas with freezing winters, digging and storing dahlia tubers is a must.
With so much information available on how to dig and store your dahlia tubers, it can easily feel overwhelming. The reality is, there’s no single “right” way to do it because we all deal with different climates and conditions. The key is to experiment with various techniques and find what works best for you.
And anytime things feel complicated or nuanced, I like to remember the underlying goal—here, it’s to get the tubers out of the ground and keep them alive through the winter. So let’s dive into how to make that happen.
The Ideal Temperature for Storing Dahlia Tubers
As a dahlia lover, I know how disheartening it can be to lose tubers over the winter. Dahlias are not cold hardy plants, so if you live in an area with freezing winters, proper tuber storage is absolutely crucial for getting them to survive and thrive year after year.
Through trial and error both in my own garden and in talking with fellow dahlia enthusiasts, I’ve learned that temperature is one of the most important factors when it comes to successfully storing dahlia tubers through the winter months.
In this article I’ll walk through everything you need to know about the ideal temperature range for storing your tubers as well as tips on the best storage locations and practices. Follow these guidelines, and you’ll have the best chance of bringing your precious dahlia tubers back to life when spring rolls around again.
When to Dig Up Your Tubers
The first step in proper dahlia tuber storage happens in the fall, when it’s time to dig up the tubers from your garden beds or containers.
Ideally, you should dig up dahlia tubers once the foliage starts to brown and die back after the first light frost Light frost occurs when temperatures dip down to the 32-36°F range and ice crystals form on surfaces This light freeze damages the tender dahlia foliage but doesn’t significantly harm the tubers underground.
It’s best to dig up the tubers before you get a hard freeze below 32°F as this can damage the tubers. But at the same time avoid digging too early while the plants are still actively growing. The tubers need time to reach full maturity underground before being stored for the winter.
Once the foliage blackens after the first light frost, the dahlias are signaling that they are going dormant for winter. This is your sign that it’s time to carefully dig up the tuber clumps.
Preparing Tubers for Storage
After digging, allow the tuber clumps to dry out for 1-2 weeks in a frost-free location out of direct sunlight. I like to place the clumps in mesh bags or cardboard boxes during this initial drying period.
You can trim back any remaining stalks and foliage to help accelerate the drying process. The tubers need to be reasonably dry to the touch before moving to long-term storage for the winter.
Before storing the tubers, it’s also wise to remove any excess soil clinging to them and trim off any sections that are rotting or damaged. Taking this time to groom your tubers will give you the best chance of avoiding issues like mold growth during storage.
Another quick tip: avoid washing the tubers with water right before storage. The extra moisture can lead to premature sprouting and rotting during dormancy.
The Ideal Temperature Range
Here’s the key info you need to know:
The ideal temperature range for storing dahlia tubers through the winter is 35-50°F.
Aim to keep your tubers around 45°F for best results.
This cool temperature keeps the tubers dormant and prevents them from sprouting too early. Warmer temperatures above 50°F run the risk of kickstarting growth before you’re ready to plant them again in spring.
On the other end of the spectrum, colder freezing temperatures below 35°F can severely damage the tubers. Extended freezing will turn them to mush and kill them completely.
Choosing the Best Storage Location
To successfully keep your tubers within the ideal 35-50°F temperature range, you’ll need to choose the right location for storage. Here are some good options to consider:
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Unheated basement, closet or garage – These spaces are likely to stay cool in the 35-50° range during winter months.
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Cool attic space – Attics can also maintain temperatures in the ideal tuber storage range, especially if they are uninsulated.
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Refrigerator crisper drawer – If your refrigerator temperature can be adjusted into the 35-50°F range, the crisper drawer makes a perfect spot.
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Insulated container stored in a cool area – An insulated cooler kept in a cold garage or basement can replicate the right conditions.
Ideally, the storage area should have cool, stable temperatures around 45°F throughout the winter storage period. Avoid anywhere that experiences freezing temperatures or excessive temperature fluctuations.
The location should also stay dark and relatively humid to keep the tubers dormant but not completely dried out.
Monitoring Tuber Condition During Storage
It’s wise to check on your stored dahlia tubers every 2-3 weeks over the winter months. Look for any signs of rotting, mold growth, sprouting, or shriveling.
If tubers seem too damp and moist, remove them from storage and dry them out again for a few days before replacing. Excess moisture leads to mold and rotting.
Conversely, if tubers are shriveled and dried out, give them a light misting of water to rehydrate before returning to storage.
Any tubers showing signs of rot should be removed immediately and discarded to prevent spreading decay to healthy tubers in storage.
Being diligent about monitoring tuber condition and adjusting humidity/moisture levels as needed will help ensure your dahlias stay healthy through the winter.
When to Plant Tubers in Spring
In early spring, bring your rested dahlia tubers out of storage once the threat of frost has passed. Wait until soil temperatures reach 60°F before planting them back in your garden beds or containers.
Tubers kept properly dormant at 35-50°F all winter will be primed and ready for another wonderful season of growth and spectacular blooms once planted again in springtime conditions.
Tips for Storing Specialty Tuber Types
The overall storage guidelines of cool (35-50°F) dark conditions apply to all types of dahlia tubers. However, a few specialty tuber types have some unique considerations:
Potted tubers – You can either remove potted tubers from pots and store as described above, or place the entire intact pot in a sealed plastic bag to retain moisture. Store potted tubers in the same 35-50°F temperature range.
Small/thin tubers – These are more prone to drying out, so monitor moisture carefully and consider a more humid storage environment. Group together to retain humidity.
Large exhibition-type tubers – May do best stored individually rather than touching to prevent rot spread.
Species dahlias like Dahlia coccinea – These tend to sprout earlier than hybrids, so err on the cooler side of the 35-50° range for storage.
No matter what type of dahlia tubers you grow, following these best practices for ideal storage temperature, humidity, and monitoring will set you up for dahlia storage success. Enjoy digging up your jewels of the garden each fall, knowing they’ll be safely slumbering through the winter to return in full bloom next year.
When to Dig Your Dahlia Tubers
One of the most common myths about digging up dahlia tubers is that you need to wait until after the first frost. Not true. While waiting does give tubers more time to mature, dahlia tubers can be dug around 90 to 100 days after the summer solstice. Dahlias grown in regions that don’t experience frost, such as Mexico or California, are proof that you can dig them up long before the first frost.
Personally, I prefer to dig mine in early October once our dahlia subscription has ended. Why? The sun is still shining. The temps are still in the double digits. The ground is still dry. And the plants aren’t a slimy, black goo. (It took just one cold, wet dahlia dig to learn this lesson!)
How to Dig Your Dahlia Tubers
Start by using a pitchfork (a shovel works just as well) to gently loosening the soil around the clump, taking care to dig far enough out from the tubers to avoid damaging them. When you dig too close, you risk shearing or piercing the clump with your tool. Once the tuber clump is free, remove as much soil as possible. A heavy, soil-loaded clump is harder to handle and makes storage more difficult. You can give the clump a gentle tap to loosen the dirt or pick away the soil by hand.
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FAQ
What temperature should dahlia tubers be stored at?
Temperature and humidity levels are the two keys to successful dahlia tuber storage. Your dahlias will need to be kept in a cool —but not freezing— environment, and they’ll need relatively high humidity. We find that 38-50 degrees F (4-10 degrees C) is best, and you’ll want to aim for 75%-85% relative humidity.
Can you store dahlia tubers in the garage?
The ideal temperature is around 40-50 degrees. An attached garage is usually safe. Unheated outbuildings typically will freeze and aren’t a good choice for storage.
Is 40 degrees too cold for dahlias?
Ideally, the optimal temperature range for dahlias is between 60°F (15.5°C) and 70°F (21°C), before you start planting your tubers. If the soil is too cold, your tubers may take forever to sprout or not even germinate at all!
Can dahlias be stored in a cooler?
If the temperature drops too low, the tubers will freeze and turn to mush. While a temperature-regulated cooler is ideal for storing dahlia tubers because it allows you to control the temperature, it’s not always feasible.
Where do you store dahlia tubers?
My advice is to find a space that is as close to this temperature range as possible: a root cellar, basement, or attic will probably be your best bet for storing dahlia tubers. For the past few years, I have been storing my dahlias in the uninsulated part of our upstairs closet, which seems to work just fine.
What temperature should dahlia tubers be stored?
Colder freezing temperatures will damage or rot the tubers. Aim for around 45°F for best results. Good locations to store dahlia tubers include: The location should stay dark and have stable, cool temperatures around 45°F all winter. Avoid anywhere that gets below freezing or fluctuates in temperature. The tubers need consistent cool conditions.
How do you store dahlias in the winter?
Dahlias are relatively easy to grow, but proper winter storage can be a struggle! Here are a few tips for storing your tubers over the winter, regardless if they are divided or not. Store at 40-45 degrees Fahrenheit. If the tubers freeze, they will turn to mush when they thaw. If they get too warm, they could rot. Humidity at about 80-90%.
Do dahlia tubers freeze?
If the temperature is too high, your tubers will begin to sprout, which you want to avoid until spring. If the temperature drops too low, the tubers will freeze and turn to mush. While a temperature-regulated cooler is ideal for storing dahlia tubers because it allows you to control the temperature, it’s not always feasible.
Should you wash dahlia tubers before storing them?
Washing Dahlia tubers before storing them is optional. Some gardeners wash them with a garden hose to remove soil, insects, and potential diseases, which helps protect the tubers during storage. However, if washed, ensure they are thoroughly dried to prevent rot. If you choose not to wash them, gently brush off excess soil.
Can you leave dahlia tubers in the ground?
To prevent this, you must lift and store your dahlia tubers until the next planting season. However, if you live in a mild climate without freezing temperatures, you can leave your tubers in the ground, and they may return year after year.