Introduction
Dahlias are the undisputed stars of the late summer garden, offering a breathtaking display of color and form that lasts until the very first frost. Whether you grow massive dinnerplate varieties or charming pompons, the joy of seeing those first buds open is a highlight for any gardener. At Longfield Gardens, we believe that the beauty of these flowers shouldn't have to end when the weather turns cold.
Learning how to harvest dahlia tubers for winter is one of the most rewarding skills you can add to your gardening repertoire. By taking a little time in the fall to lift and store your tubers, you can enjoy your favorite varieties year after year. This process also allows your dahlia collection to grow, as healthy tubers often multiply beneath the soil throughout the season.
This guide will walk you through the simple, step-by-step process of digging, cleaning, and storing your dahlia tubers. We have designed these instructions for gardeners of all skill levels, focusing on the practical steps that lead to success. With the right timing and a bit of care, you can ensure your dahlias rest safely through the winter and are ready to bloom again next summer. Whether you grow dinnerplate varieties or more compact forms, the process is the same.
Determining the Right Time to Harvest
Timing is everything when it comes to harvesting dahlia tubers. While it can be tempting to start digging as soon as the weather cools, the tubers actually benefit from staying in the ground as long as possible. During the late summer and early autumn, the plant focuses its energy on building up starch reserves in the tubers, which helps them survive the long winter dormancy.
The most reliable signal for harvest is the first killing frost. You will know it has arrived when the once-vibrant green foliage turns dark brown or black almost overnight. This change may look a bit sad, but it is actually a natural part of the plant's life cycle. The frost tells the plant to stop upward growth and shift all its remaining energy into the tubers below the ground.
If you live in a climate where a hard frost does not occur until very late in the year, you should aim to harvest your tubers by mid-November. The goal is to get them out of the ground before the soil itself freezes solid. Freezing temperatures within the soil can damage the tuber tissue, leading to rot. If your plants are still green but the calendar says winter is approaching, you can manually trigger the dormancy process by cutting the plants down yourself.
The Curing Period in the Ground
Many experienced gardeners prefer to wait a few days after the first frost before they start digging. Once the foliage is blackened, you can cut the stems back to about four to six inches above the soil line. Leaving the tubers in the ground for five to seven days after cutting allows them to "cure."
During this short wait, the skin of the tubers begins to toughen up. This thicker skin acts as a protective barrier, making the tubers more resilient during the handling and storage phases. This waiting period also encourages the "eyes" or growth points to become more visible, which is incredibly helpful if you plan on dividing your tubers before storing them.
What to do next:
- Watch your local weather forecast for the first signs of frost.
- Once the foliage turns black, cut the stems down to about 5 inches.
- Wait about one week before you begin the digging process.
Preparing Your Tools for a Smooth Harvest
Having the right tools ready will make the harvesting process much easier and safer for the plants. Dahlia tubers are surprisingly fragile, especially at the "neck" where the tuber connects to the main stem. A little preparation goes a long way in preventing accidental damage.
The most important tool for this job is a garden pitchfork or a potato fork. While a shovel can work, it is much more likely to slice through the tubers hidden beneath the surface. A pitchfork allows you to loosen the soil and lift the entire clump with much less risk of cutting the individual roots.
You will also need a pair of sharp, clean bypass pruners or loppers. These are used to cut through the thick, woody stems of the dahlia plants. Before you begin, it is a great idea to wipe your blades with a simple solution of rubbing alcohol or a diluted bleach mixture. This prevents the spread of any soil-borne diseases from one plant to another.
Finally, gather your labeling supplies. Nothing is more confusing in the spring than a box of mystery tubers. Have a permanent marker and some garden tags or masking tape ready so you can label each clump as soon as it comes out of the ground.
How to Dig Dahlia Tubers Without Damage
When you are ready to dig, the most important rule is to give the plant plenty of space. Dahlia tuber clumps can grow much wider than you might expect, sometimes extending 12 inches or more from the main stem.
Start by Inserting your pitchfork into the soil about a foot away from the center of the plant. Gently push the fork down and lean back on the handle to loosen the earth. Work your way in a full circle around the plant, lifting slightly at each point. This "loosening" phase is crucial because it breaks the tension of the surrounding soil without putting stress on the tubers themselves.
Once you have completed the circle, insert the fork deeply under one side of the clump and gently pry it upward. Use your other hand to steady the "stem handle" you left behind, but do not use the stem to pull the plant out of the ground. Pulling on the stem can snap the necks of the tubers, making them unable to grow next year.
Slowly lift the entire mass of soil and tubers out of the hole. It may feel heavy, especially if your soil is damp or contains a lot of clay. Set the clump gently on the grass or a nearby tarp. You will likely see a large ball of dirt with tubers poking out; this is perfectly normal and a sign of a healthy, productive plant.
Cleaning and Initial Drying
Once the tubers are out of the ground, you need to remove the excess soil. How you do this depends largely on your soil type. If you have light, sandy soil, you can often just give the clump a gentle shake or use a soft brush to remove the dirt. If your soil is heavy clay, you may need a bit more help. For a closer look at tuber structure, see Dahlia Tubers: What You Need to Know.
Using a garden hose with a gentle spray setting is a common way to clean tubers. Wash away the clods of dirt until you can see the individual tubers and the "crown" where they meet the stem. Avoid using a high-pressure blast, as this can tear the skin. It is important to remove the soil because dirt can harbor fungi and bacteria that lead to rot during the winter months.
After washing, find a protected spot out of direct sunlight and away from freezing temperatures. A garage, shed, or covered porch works well. Place the tubers upside down, with the cut stems facing the ground. This allows any water that trapped inside the hollow stems to drain out. If water sits inside the stem, it can cause the crown of the tuber to rot from the inside out.
Let the tubers dry in this position for about 24 to 48 hours. You want the surface of the tubers to feel dry to the touch, but you don't want them to stay out so long that they begin to shrivel or look like raisins.
To Divide or Not to Divide
One of the most common questions we hear is whether you should divide the dahlia clumps in the fall or wait until the spring. The truth is that both methods work, and the best choice depends on your personal preference and storage space.
Dividing the dahlia clumps in the fall is popular because the tubers are softer and easier to cut. It also saves a significant amount of space in your storage containers. However, the "eyes" (the small bumps where next year's growth begins) can be very difficult to see in the fall. If you divide them now, you might accidentally cut a tuber that doesn't have an eye, which means it won't be able to sprout.
Dividing in the spring is often easier for beginners. After a winter of rest, the eyes on the tubers will begin to swell and may even turn slightly pink or green. This makes it very obvious where to make your cuts. The downside is that the tubers become much tougher and more woody over the winter, requiring a very sharp knife and more physical effort to separate.
Regardless of when you choose to divide, the rule for a viable tuber remains the same: every piece must have a "body" (the fat part of the root), a "neck" (the narrow part), and a "crown" with at least one visible eye. If you aren't sure, it is perfectly fine to store the entire clump whole and deal with the division in the spring.
Key Takeaway: If you are a beginner, consider storing your dahlia clumps whole. This protects the fragile necks and makes it much easier to identify the growth eyes when you are ready to plant in the spring.
Choosing the Best Storage Medium
Successfully overwintering dahlias is a balancing act. You want to keep the tubers cool enough to stay dormant but warm enough that they don't freeze. You also need to keep them hydrated enough so they don't shrivel, but dry enough so they don't rot. Using a storage medium helps regulate these conditions. For a broader overview of growing and care, see All About Dahlias.
There are several effective materials you can use to pack your tubers:
- Peat Moss: This is a classic choice. It is lightweight and holds just enough moisture to prevent shriveling.
- Vermiculite: This mineral is excellent for moisture control and provides good insulation.
- Wood Shavings: Cedar or pine shavings (often sold as animal bedding) are affordable and provide great airflow.
- Newspaper: If you only have a few tubers, wrapping them individually in several layers of dry newspaper can work well.
Avoid using plastic bags that are sealed airtight. Tubers are living things and need a small amount of oxygen. If they are sealed in plastic, moisture will build up and they will likely rot within weeks. Instead, use cardboard boxes, plastic milk crates, or open plastic bins.
When packing, place a layer of your chosen medium in the bottom of the container. Lay the tubers or clumps in a single layer so they aren't touching each other. Cover them with more medium and repeat the process until the box is full. This "nesting" prevents a single rotten tuber from spreading decay to its neighbors.
The Ideal Winter Storage Environment
Where you keep your boxes of tubers is just as important as how you pack them. The ideal temperature for dahlia storage is between 40°F and 50°F. If the temperature stays consistently above 60°F, the tubers may try to wake up and start growing too early. If the temperature drops below 35°F, you run the risk of them freezing.
An unheated basement, a root cellar, or a frost-free crawl space are usually the best locations. Some gardeners use an attached garage, but you must be careful that the temperature doesn't plummet during a cold snap. Placing your storage boxes on a wooden pallet or a shelf rather than directly on a cold concrete floor can provide an extra layer of insulation.
Humidity also plays a role. Most homes are quite dry in the winter due to heating systems. If you notice your tubers starting to look wrinkled after a month or two, you can lightly mist the storage medium with water. You don't want it to be wet—just a tiny bit of dampness is enough to keep the tubers plump.
Monitoring Your Tubers Through the Winter
Overwintering dahlias is not a "set it and forget it" task. We recommend checking on your tubers at least once a month. This small effort can save your entire collection from a surprise issue.
When you perform your monthly check, look for two things: rot and shriveling. If you find a tuber that feels soft, mushy, or has a bad odor, remove it immediately and throw it away. Rot can spread quickly through a storage box, so catching it early is vital.
If the tubers look extremely wrinkled or feel light and hollow, they are dehydrating. Give the packing material a very light spray of water and move them to a slightly cooler spot if possible. A healthy tuber should feel firm, much like a fresh potato from the grocery store.
By keeping a close eye on your tubers, you ensure that the majority of them will make it through to spring in excellent condition. At Longfield Gardens, backed by our 100% Guarantee, we have found that this simple routine is the secret to a successful dahlia garden year after year.
Preparing for Spring Planting
As the days begin to lengthen in late winter or early spring, you may notice small sprouts appearing on your tubers. This is an exciting sign that they are ready to grow! If you live in a cold climate with a short growing season, you can "wake up" your tubers indoors about four to six weeks before the last frost date. For more spring planting options, browse our spring-planted bulbs.
To do this, simply bring the tubers into a warmer room (around 60-65°F) and give them a bit more light. You can even pot them up in some moist potting soil to give them a head start. By the time the soil in your garden has warmed up to 60°F, you will have established plants ready to go into the ground.
Remember that dahlias are tropical plants at heart. They love the sun and warm soil. While it is tempting to plant them as soon as the snow melts, waiting until the threat of frost has passed and the soil is warm will actually lead to faster growth and earlier blooms.
What to do next:
- Check your tubers once a month during winter for any soft spots.
- In early spring, move your storage boxes to a slightly warmer area.
- Wait for the soil to reach 60°F before planting them back in the garden.
Conclusion
Harvesting dahlia tubers for the winter may seem like a big task at first, but it quickly becomes a satisfying autumn ritual. It is a way to transition from the busy summer growing season into the quiet reflection of winter. By following these simple steps, you are protecting your investment and ensuring that your garden will be even more beautiful next year.
The key points to remember for a successful harvest are:
- Wait for the first frost to signal the end of the season.
- Use a pitchfork to lift tubers gently, avoiding the "stem handle."
- Clean and dry the tubers thoroughly to prevent rot.
- Store them in a breathable medium at a cool, consistent temperature.
At Longfield Gardens, we are here to help you succeed every step of the way. Whether you're preserving pompons or other dahlia forms, gardening is a journey of discovery, and each year you overwinter your dahlias, you will learn more about what works best in your unique climate. We hope this guide gives you the confidence to preserve your favorite blooms and keep your garden growing for many seasons to come. If you're planning ahead, browse our Shop All Spring Planted Bulbs.
"There is a special kind of satisfaction in holding a dormant tuber in your hand during the winter, knowing that it holds the potential for a five-foot-tall plant covered in stunning blossoms."
FAQ
Do I have to dig up my dahlias every year?
This depends entirely on your USDA hardiness zone. If you live in Zone 8 or warmer, your soil likely stays warm enough that dahlia tubers can survive the winter in the ground. However, even in warm zones, many gardeners choose to dig and divide them every few years to prevent the clumps from becoming overcrowded and to improve bloom quality.
What happens if I dig my tubers before the first frost?
You can certainly dig your tubers before the first frost if you need to, but they may not store as well. The frost signals the plant to go dormant and toughens the skin of the tubers. If you must dig early, try to wait until at least mid-autumn so the tubers have had enough time to develop their starch reserves. For step-by-step help, see How to Lift and Store Dahlia Bulbs.
Can I use plastic bags for storage if I leave them open?
While you can use plastic bags if they are left completely open, it is not the most recommended method. Plastic tends to trap moisture against the tubers, which is the leading cause of rot. Cardboard boxes or wooden crates are much safer because they allow for natural air exchange and help maintain a more stable humidity level.
Why did my tubers turn to mush in storage?
Mushy tubers are usually a result of one of two things: freezing or rot. If the storage area dropped below freezing, the water inside the tuber cells expanded and destroyed the tissue. Rot is typically caused by too much moisture or poor airflow. To prevent this, ensure tubers are dry before packing and check them monthly to remove any that show early signs of decay.
