Table of Contents
- Introduction
- The Importance of Proper Winter Storage
- When to Begin the Lifting Process
- Preparing the Plants for Digging
- How to Lift Your Dahlia Tubers Safely
- Cleaning and Drying Your Tubers
- Dividing Your Dahlia Tubers
- Selecting the Best Storage Medium
- Finding the Perfect Storage Location
- Monitoring Your Tubers Through Winter
- The Pot Root Method
- Preparing for Spring
- Summary of Success
- FAQ
Introduction
The end of the gardening season brings a special kind of satisfaction. After a summer filled with the spectacular colors and dinnerplate-sized blooms of your dahlias, it is time to tuck them away for their winter nap. Saving these tubers is one of the most rewarding parts of gardening. It allows you to grow your collection year after year and share your favorite varieties with friends.
At Longfield Gardens, we want to help you feel confident as you transition your garden from autumn to winter, and our Dahlia Collections make it easy to plan ahead. Storing dahlia tubers, which many gardeners simply call "bulbs," is a straightforward process that anyone can master with a few simple steps. This guide will walk you through the entire process, from the first frost to spring planting. You will learn how to lift, clean, and protect your plants so they stay healthy and ready to grow again.
Storing your dahlia tubers is a rewarding way to preserve your garden investment and ensure a beautiful display for the following season.
The Importance of Proper Winter Storage
Dahlias are native to the warm climates of Mexico and Central America. Because they are not built for freezing temperatures, they cannot stay in the ground over winter in most parts of the United States. In USDA zones 7 and colder, the freezing soil will turn the moisture inside the tubers into mush. Even in warmer areas, heavy winter rains can cause the tubers to rot if the soil does not drain quickly.
Lifting your dahlias allows you to take control of their environment. By keeping them in a cool, dark, and dry place, you mimic the dormant period they need to recharge. This process also gives you a chance to inspect your plants. You can see which varieties grew the most and ensure you are only saving the healthiest stock for next year.
When to Begin the Lifting Process
Timing is the most important factor when learning How to Overwinter Dahlia Tubers. You want the tubers to stay in the ground as long as possible so they can mature. As the days get shorter in the fall, the plant shifts its energy from making flowers to storing starches in the roots. These starches are the fuel the plant will use to sprout in the spring.
Waiting for the First Frost
The best signal to start is the first "killing frost." This is the night when temperatures drop low enough to turn the green leaves and stems black or dark brown. While it might look a little sad to see your vibrant plants change so quickly, this is actually a helpful turning point.
Once the top of the plant dies back, the tubers begin to "cure" in the soil. The skins on the tubers toughen up, which makes them much more resistant to bruising and rotting during storage. Most gardeners wait about five to seven days after the first frost before they start digging. If your area does not get a frost by mid-November, you can simply cut the plants back manually to start the process.
The Benefits of Curing
Curing is simply a period where the tuber prepares for dormancy. If you dig them up while the plant is still actively blooming, the skins are often thin and fragile. Waiting a few days after the frost helps the "eyes" become more visible. The eyes are the small bumps on the crown where next year’s stems will grow. Being able to see these eyes makes it much easier to divide your tubers later.
What to do next:
- Monitor your local weather forecast for the first evening frost.
- Leave the plants in the ground for about a week after the foliage turns black.
- Prepare your storage bins and labeling materials while you wait.
Preparing the Plants for Digging
Before you pick up a shovel, you need to prepare the "above-ground" part of the plant. This makes the lifting process much cleaner and keeps your garden organized.
Cutting Back the Stems
Use a pair of sharp, clean loppers or garden shears to cut the main stalk. Aim for a height of about four to six inches above the soil line. This remaining piece of stem acts as a sturdy handle. It helps you lift the clump without having to grab the fragile tubers themselves.
Be aware that dahlia stems are often hollow. After you cut them, they may contain some water. This is normal, but you should avoid letting excessive water sit in the hollow tube for too long, as this can encourage rot in the crown. Some gardeners like to cover the open tops with a small piece of aluminum foil if heavy rain is expected before they dig.
The Power of Labeling
Nothing is more frustrating than having a box of mystery tubers in the spring. Before you lift the plant, make sure the variety name is securely attached. You can wrap a waterproof tag around the stem handle or use a permanent marker to write directly on the skin of a large tuber once it is dry.
At our trial garden at Longfield Gardens, we find that labeling the stem immediately after cutting is the safest way to keep track of colors and sizes. If you have multiple plants of the same variety, you can group them in labeled crates.
How to Lift Your Dahlia Tubers Safely
The actual digging process requires a gentle touch, and Dahlia Tubers: What You Need to Know explains the anatomy that makes these clumps so fragile. Dahlia tubers are connected to the main stem by a narrow "neck." This neck is very fragile. If the neck breaks or gets a deep crack, the tuber usually cannot grow a new sprout and will eventually rot.
Choosing the Right Tools
A garden fork is often better than a shovel for this job. A shovel can easily slice through a hidden tuber, while the tines of a garden fork are more likely to slide around them. If you do use a shovel, make sure it is sharp and that you are working well away from the center of the plant.
The Lifting Technique
Start by placing your fork about 10 to 12 inches away from the main stem. This ensures you are outside the main "clump" zone. Push the fork deep into the soil and gently pry upward. Move in a circle around the plant, loosening the soil on all sides.
Once the soil is loose, place one hand on the stem handle and the other under the clump with the fork. Lift the entire mass out of the ground slowly. Do not shake it violently to remove the dirt. Instead, use a small stick or your fingers to gently poke away large clods of soil.
Cleaning and Drying Your Tubers
Once the tubers are out of the ground, they need to be cleaned. There are two common schools of thought on this: washing with water or brushing off dry dirt.
To Wash or Not to Wash?
If you have heavy clay soil, washing the tubers with a gentle stream from a garden hose is often necessary. It allows you to see the health of the tubers and find the eyes more easily. If you have light, sandy soil, you can usually let the clump dry for an hour and then simply brush the dirt away.
If you do wash your tubers, it is vital to let them dry completely before putting them in storage. Moisture is the biggest enemy of a dormant tuber. Any water trapped in the nooks and crannies of the clump can lead to mold or fungal growth.
The Initial Curing Phase
Place your cleaned tubers in a frost-free, shaded area with good air circulation. A garage or a covered porch works perfectly. Lay them out on a piece of cardboard or a mesh screen. Do not stack them deeply; a single layer is best.
Let them sit for one to three days. During this time, the outer skin will continue to toughen. You will notice the tubers feel less "plump" and more like a firm potato. This is exactly what you want.
Key Takeaway: Drying is a critical step. Tubers must be dry to the touch before they go into containers, but they should not be left out so long that they become shriveled and leathery.
Dividing Your Dahlia Tubers
A single dahlia plant can produce a large clump of 10 to 20 tubers by the end of the season. You have a choice: you can store the entire clump as it is, or you can divide it into individual tubers now.
Storing Whole Clumps
Storing the whole clump is the easiest method for beginners. The tubers stay protected by the surrounding structure, and they are less likely to dry out completely. The downside is that whole clumps take up a lot of space in your storage bins. If you choose this route, you will simply divide them in the spring when the eyes are bulging and easy to see.
Dividing in the Fall
Many experienced gardeners prefer to divide in the fall because the tubers are softer and easier to cut. To do this, you will need a sharp, sterilized knife. Each individual tuber must have three things to be viable:
- A Body: The swollen part that holds the energy.
- A Neck: The narrow part that connects the body to the crown.
- An Eye: A small bud located on the crown (the area where the neck meets the old stem).
If a tuber breaks off without a piece of the crown and an eye, it will not grow. When you finish dividing, let the "cut" ends dry for 24 hours to form a callus before packing them away.
Tool Safety and Sanitation
When moving from one plant variety to another, it is a good idea to dip your cutting tools in a solution of one part bleach to ten parts water. This simple step prevents the spread of any soil-borne diseases or viruses between your different dahlia varieties.
Selecting the Best Storage Medium
You cannot simply throw dahlia tubers into an empty box and hope for the best. They need a "buffer" material. This material helps regulate humidity. It keeps the tubers from getting too wet (which causes rot) or too dry (which causes shriveling).
Popular Storage Materials
- Vermiculite: This is often considered the gold standard. It is a natural mineral that holds a tiny bit of moisture but stays very airy.
- Peat Moss: A common and affordable choice. It is excellent at absorbing excess moisture. If the peat moss feels bone-dry, you may need to mist it very lightly before use.
- Wood Shavings: The kind used for animal bedding works well. It provides great air circulation.
- Newspaper: Some gardeners wrap individual tubers in several layers of newspaper and then stack them in boxes.
At Longfield Gardens, we suggest starting with whatever material is most accessible to you. The goal is to create a cozy, stable environment where the tubers are not touching each other. This prevents a single spoiled tuber from spreading rot to the rest of the batch.
Finding the Perfect Storage Location
The "where" is just as important as the "how." You are looking for a location that stays consistently cool but never freezes.
The Ideal Temperature Range
The sweet spot for dahlia storage is between 40°F and 50°F. If the temperature stays above 50°F, the tubers may think it is spring and try to sprout too early. If the temperature drops below 35°F, you risk losing the whole batch to frost damage.
Common Storage Spots
- Unheated Basements: Usually provide the most consistent temperatures.
- Attached Garages: Good, but you must ensure the box is off the concrete floor and away from drafty doors.
- Root Cellars or Crawl Spaces: Excellent for humidity control, though you should watch for rodents who might find the tubers a tasty winter snack.
What to do next:
- Place a thermometer in your intended storage area for a few days to check the temperature.
- Choose a sturdy plastic bin or a cardboard box for your tubers.
- If using plastic, leave the lid slightly ajar to allow for minimal air exchange.
Monitoring Your Tubers Through Winter
Storing your dahlias is not a "set it and forget it" task. You should check on your tubers about once a month. This small effort can save your entire collection.
What to Look For
When you open your bins, do a quick visual and "feel" test.
- If they look shriveled: The storage medium is too dry. Give it a very light misting of water with a spray bottle. You want them to stay firm like a fresh carrot.
- If you see fuzzy mold: The environment is too damp. Remove the affected tubers immediately. Leave the lid off the box for a day to let some moisture escape.
- If a tuber feels soft or squishy: This is rot. Throw it away immediately so it doesn't infect its neighbors.
Dealing with Rot
If you find a small spot of rot on a large tuber, you can sometimes save it. Use a clean knife to cut away the soft part until you see clean, white flesh. Let that spot dry and callus over before putting it back in the box. However, if the rot has reached the neck or the crown, it is usually best to discard it.
The Pot Root Method
If you have a variety that is notoriously difficult to store, you might consider the "pot root" method. Instead of digging the tubers out of the soil, some gardeners grow small dahlias in pots all season. A compact option like Dahlia Decorative Sweet Nathalie is well suited to this approach. In the fall, they simply cut the plant back and store the entire pot, soil and all, in a cool place.
The soil acts as a natural insulator and keeps the tubers at a very stable humidity level. In the spring, you simply bring the pot into the light and start watering. This is a great "easy win" for beginners who are nervous about the digging and cleaning process.
Preparing for Spring
As winter winds down and the ground begins to thaw, your dahlias will start to wake up. You may notice tiny pink or green sprouts appearing on the crowns. This is an exciting sign that your storage was successful!
About four weeks before your last expected frost, you can bring the bins into a warmer room. This "pre-sprouting" gives the plants a head start, and How to Plant and Grow Dahlia Tubers has more spring planting basics. By the time the soil in your garden reaches 60°F, your dahlias will have strong eyes or even small stems, ready to be planted back into the sun.
Summary of Success
Storing dahlia bulbs does not have to be a source of stress. By following the natural cycle of the plant and providing a stable winter home, you can enjoy these spectacular flowers year after year.
- Wait for a frost to signal the plant to go dormant.
- Lift the tubers gently with a fork to protect the fragile necks.
- Dry the tubers thoroughly before packing them away.
- Use a storage medium like vermiculite or peat moss to regulate moisture.
- Keep the bins in a cool (40–50°F), dark place.
- Check monthly for shriveling or rot.
"Gardening is a cycle of growth and rest. By taking the time to store your tubers properly, you are participating in the most rewarding part of the garden's rhythm."
Whether you are a seasoned pro or a first-time grower, the satisfaction of seeing those first green shoots in the spring makes all the effort worthwhile. For more tips on growing a vibrant garden, you can explore our other guides and browse the Dahlia Dinnerplate Summer Lovin Collection to expand your collection.
FAQ
How long can dahlia tubers stay out of the ground before they die?
Dahlia tubers can usually stay out of the ground for about a week during the cleaning and drying phase without any issues. However, if they are left in a warm, dry room for longer than that, they will begin to shrivel and lose the energy they need to sprout. It is best to get them into their storage medium within three to four days of digging.
Can I store dahlia tubers in the refrigerator?
While a refrigerator is cool, it is usually not the best place for dahlia tubers because the humidity is often too low, and it may be slightly too cold. If you must use a refrigerator, keep them in the vegetable crisper drawer in a bag of moist vermiculite. Avoid storing them near ripening fruits like apples, which release gases that can damage the tubers. For another big-bloom option next season, see Dahlia Dinnerplate Islander.
Do I need to wash the dirt off the tubers before storing them?
You do not strictly need to wash them, but it is highly recommended if your soil is heavy or holds a lot of moisture. Washing allows you to inspect the tubers for pests or rot and makes it much easier to identify the "eyes" for dividing. If you choose not to wash them, ensure the clumps are completely dry before you brush off the excess soil.
What should I do if my dahlia tubers look shriveled in mid-winter?
Shriveling is a sign that the tubers are losing too much moisture to the air. To fix this, lightly mist the storage material (like peat moss or wood shavings) with water. You do not want the material to be soaking wet, just slightly damp to the touch. This small boost in humidity will usually help the tubers firm back up within a week. If you're planning a fresh planting, try the Dahlia Assorted Sunlit Jewel Collection for a colorful mixed display.
