Introduction
Dahlias are the undisputed stars of the late-summer garden, offering a spectacular range of colors and shapes that keep our landscapes vibrant until the first frost. There is a special kind of satisfaction in seeing a dinnerplate-sized bloom reach its peak or harvesting a fresh bouquet of pompon dahlias for your kitchen table. At Longfield Gardens, we believe every gardener can enjoy these stunning flowers year after year by mastering a few simple winter storage techniques.
Whether you are a first-time grower or a seasoned enthusiast, knowing how to protect your investment during the cold months is the key to a successful spring start. This guide will walk you through the process of harvesting, cleaning, and packing your tubers to ensure they stay healthy and viable until it is time to plant again. By following these steps, you can turn a single season of beauty into a lifetime of blooms.
Storing dahlia tubers is a straightforward process that centers on managing two main factors: temperature and moisture.
Why Winter Storage Matters
In most parts of the United States, dahlias are treated as tender perennials. This means that while the plants thrive in the heat of summer, the tubers—the underground storage roots—cannot survive the freezing ground temperatures of northern winters. If you live in USDA hardiness zones 8 through 11, you may be able to leave your dahlias in the ground with a thick layer of mulch. However, for gardeners in zones 3 through 7, lifting and storing tubers is a necessary annual ritual.
Storing tubers does more than just keep the plants alive. It allows you to inspect your stock, divide your clumps to create more plants for free, and ensure that your favorite varieties remain vigorous. When you get the storage conditions right, you are essentially hitting the "pause" button on the plant's life cycle, keeping it dormant until the soil warms up again in May or June.
Timing the Harvest
The most common question gardeners ask is when exactly they should begin the digging process. While it may be tempting to get a head start on fall chores, timing is everything when it comes to tuber health.
The Killing Frost
For the best results, wait until a "killing frost" has turned the foliage of your dahlias black or brown. This frost sends a signal to the plant that the growing season is over. Once the top growth dies back, the plant focuses all its remaining energy on the tubers, helping them "cure" and toughen up for their winter nap.
If you live in an area where a hard frost doesn't occur until very late in the year, you can manually trigger this process by cutting the plants back to about six inches in early to mid-November.
The Waiting Period
After the foliage has turned black or you have cut the stalks down, try to leave the tubers in the ground for another 5 to 7 days. This brief waiting period is a "quiet winner" in the storage process. It encourages the tubers to develop "eyes"—the small bumps or growth points that will become next year's stems. When the eyes are more visible, it makes the process of dividing the clumps much easier.
If the weather forecast predicts a deep, ground-freezing freeze or heavy, sustained rains that could cause rot, it is perfectly fine to dig them up sooner. Gardening always requires a bit of flexibility based on your local conditions.
How to Dig Dahlias Carefully
Dahlia tubers are surprisingly fragile, especially at the "neck," which is the narrow part where the tuber connects to the main stem. If the neck is broken or badly cracked, the tuber usually won't grow, even if the rest of the root looks healthy.
Loosening the Soil
Start by cutting the stalks down to about 4 or 6 inches above the ground if you haven't already. This "handle" will help you identify the center of the clump, but you should never use it to pull the plant out of the earth.
Use a sturdy garden fork or a spade. Dig a circle around the plant, staying at least 12 inches away from the main stem. This ensures you don't accidentally slice through the tubers that have grown outward during the summer. Gently pry upward from all sides to loosen the soil.
Lifting the Clump
Once the soil is loose, slide your shovel or fork deep under the clump and lift it gently. If you encounter resistance, do not force it. Instead, clear more soil away until the clump comes up freely. Shake off the heaviest clods of dirt, but don't worry about getting them perfectly clean just yet.
Key Takeaway: Protect the Necks The connection point between the tuber and the stem is the most vital part of the plant. Always lift from underneath the clump with a tool rather than pulling by the stalks to avoid snapping these delicate connections.
Cleaning and Preparing for Storage
Once your tubers are out of the ground, they need a little bit of grooming before they go into their winter containers.
Washing vs. Brushing
There are two schools of thought on cleaning dahlias. If you have light, sandy soil, you can often just let the clumps dry for a few hours and then gently brush away the dirt with your hands or a soft brush.
If you have heavy clay soil, it is usually better to wash the tubers with a gentle stream of water from a garden hose. Removing the soil makes it easier to see the eyes and check for any signs of damage or rot. If you wash them, ensure you do so in a way that allows the water to drain out of the hollow stalks. Turning the clumps upside down for a few hours is a simple way to prevent water from pooling in the crown, which can lead to rot.
Trimming the "Hair" Roots
You will notice many thin, thread-like roots hanging off the main tubers. These are feeder roots that the plant used to gather nutrients during the summer. They serve no purpose during dormancy and can actually hold excess moisture that leads to mold. Use a clean pair of snips to trim these away, leaving the main, thick tubers smooth and clean.
The Curing Phase
Before packing them away, tubers need to dry—but not dry out completely. Find a cool, shaded spot like a garage or a covered porch. Lay the tubers out on a piece of cardboard or a wooden pallet. Avoid placing them directly on cold concrete, as this can wick away too much moisture.
Let them sit for 24 to 48 hours. The skin of the tuber should feel dry to the touch, and any cut surfaces (like where you trimmed the stalk) should begin to callous over.
To Divide or Not to Divide?
One of the biggest decisions you will make is whether to divide your dahlia clumps in the fall or wait until the spring. Both methods have benefits, and the choice depends on your schedule and storage space.
Dividing in the Fall
Many gardeners prefer to divide in the autumn because the tubers are softer and easier to cut. Dividing now also saves a significant amount of storage space, as you are only keeping the viable tubers rather than the entire bulky clump.
When dividing, each individual tuber must have a piece of the "crown" (the area where the tuber meets the stem) and at least one "eye." A tuber without an eye is a "blind" tuber and will not produce a plant. Use a sharp, sterilized knife to make clean cuts.
Dividing in the Spring
If you are busy in the fall, you can store the entire clump whole. In the spring, the eyes will often be starting to sprout, making them very easy to identify. The downside is that the tubers can become quite woody and hard over the winter, requiring more effort to cut.
What to do next:
- Use a permanent marker to write the variety name directly on the skin of the tuber.
- Discard any tubers that feel soft, mushy, or hollow.
- Sterilize your cutting tools with a quick wipe of rubbing alcohol between plants.
- Ensure each division has a visible eye or a piece of the crown.
- Let any new cuts dry for 24 hours before packing.
Choosing Your Packing Material
The goal of storage is to keep the tubers dormant and plump. If the air is too dry, they will shrivel up like raisins. If it is too wet, they will rot. The material you pack them in acts as a buffer to maintain that perfect middle ground.
Vermiculite
Vermiculite is a popular choice for many enthusiasts. It is a lightweight mineral that is excellent at regulating moisture. It can absorb excess humidity while providing enough insulation to keep the tubers from drying out.
Peat Moss or Coco Coir
Slightly dampened peat moss or coco coir is a classic storage medium. It is inexpensive and easy to find. If you use this, make sure it is only "barely" damp—if you squeeze a handful, no water should come out.
Pine Wood Shavings
Commonly sold as pet bedding, kiln-dried pine shavings are a clean and effective option. They provide good air circulation and are very easy to handle in the spring when it’s time to unpack.
The Plastic Wrap Method
Some gardeners have great success wrapping individual, cleaned tubers tightly in plastic kitchen wrap (Saran wrap). This method relies on the tuber's own internal moisture to stay plump. It is a space-saver, but it requires that the tubers be perfectly clean and dry before wrapping to prevent mold.
Ideal Storage Conditions
Once packed, your dahlias need a specific environment to survive the winter successfully. Think of this as the "Three Bears" of gardening: not too hot, not too cold, but just right.
The Temperature Sweet Spot
The ideal temperature for dahlia storage is between 40°F and 50°F (4°C to 10°C).
- If it's too cold: If the temperature drops below freezing (32°F), the cells in the tubers will rupture, and they will turn into mush when they thaw.
- If it's too warm: If the temperature stays above 55°F, the tubers may try to wake up and sprout prematurely, or they may shrivel due to high metabolic activity.
Unheated basements, crawl spaces, or insulated garages are usually the best spots. Avoid storing them in a refrigerator used for food, as ripening fruits give off ethylene gas which can damage the tubers.
Managing Humidity
Dahlias prefer a humidity level of about 80% to 90%. Since most home storage areas are drier than this, your packing material and containers do most of the work. You can use plastic bins with the lids slightly ajar, or cardboard boxes lined with newspaper.
If you notice the packing material feels bone-dry in mid-winter, a light misting with a spray bottle can help. Just be careful not to overdo it; you want the material to be humid, not wet.
Winter Monitoring and Maintenance
Successful dahlia storage isn't a "set it and forget it" task. We recommend checking on your tubers about once a month. This small habit allows you to catch minor issues before they become big problems.
Checking for Rot
If you find a tuber that has become soft, slimy, or smells unpleasant, remove it immediately. Rot can spread quickly through a box, so removing the "bad apple" protects the rest of your stock.
Checking for Shriveling
If your tubers are starting to look wrinkled or feel lightweight, they are losing too much moisture. To fix this, lightly mist the packing material with water or add a slightly damp piece of newspaper to the top of the container.
Checking for Mold
A small amount of surface mold can sometimes appear on the cut ends of the stalks. If it’s just a light dusting, you can usually wipe it off and leave the container open for a day to improve air circulation. If the mold is fuzzy and deep, you may need to trim back the affected area and ensure the tubers aren't too damp.
Toxicity and Safety
While dahlias are a joy in the garden, it is important to remember that they are not meant for consumption. Dahlia tubers can be toxic to dogs, cats, and horses if eaten, often causing digestive upset or skin irritation. When storing your tubers, keep them in a secure location where pets and curious children cannot reach them. Always wash your hands after handling tubers or garden chemicals.
Preparing for Spring
As the days grow longer and the ground begins to thaw, your dahlias will naturally start to wake up. You may notice the "eyes" beginning to swell or even send out small green shoots while still in their storage boxes. This is an exciting sign that your storage was successful!
Don't rush to plant them too early. Dahlias love warm soil (at least 60°F). While you wait for the right outdoor conditions, you can "pre-start" your tubers indoors in pots about 4 to 6 weeks before the last frost date. This gives you a head start on the season and results in earlier blooms.
At Longfield Gardens, we take pride in providing high-quality tubers that are true to variety and ready to perform. We stand behind our quality with a 100% guarantee; we want your first growing season to be a resounding success. If you ever have a concern about the condition of your delivery or the performance of your plants, our team is here to help you find a solution.
Conclusion
Knowing how to store dahlia tubers is one of the most rewarding skills a gardener can develop. By simply managing temperature and moisture, you can preserve your favorite flowers and expand your garden year after year. The process of digging, cleaning, and packing is a peaceful way to wrap up the gardening season and look forward to the beauty of the next.
- Wait for the first frost to signal dormancy before digging.
- Handle tubers gently to protect the fragile necks.
- Store in a cool (40-50°F), dark place with consistent humidity.
- Check your tubers monthly to ensure they stay plump and rot-free.
The effort you put in during the autumn pays off in a spectacular display of color all summer long. We invite you to explore the wide world of dahlias and enjoy the simple pleasure of watching a tiny tuber transform into a magnificent floral display.
FAQ
How can I tell if my dahlia tubers have rotted during storage?
A rotten tuber will feel soft, mushy, or hollow when squeezed gently, whereas a healthy tuber should feel firm, similar to a potato. You may also notice a dark, discolored appearance or an unpleasant, sour smell. If you find a tuber with rot, it is best to discard it immediately to prevent the decay from spreading to neighboring healthy tubers.
Can I store my dahlia tubers in the refrigerator?
While a refrigerator provides a consistent cool temperature, it is generally not recommended for dahlia storage. Most refrigerators are very low in humidity, which causes tubers to shrivel quickly. Additionally, if you store fruits like apples or pears in the same fridge, they release ethylene gas as they ripen, which can cause the dahlia tubers to rot or fail to sprout in the spring. For shipping timing and zone-based order windows, see our Shipping Information.
What should I do if my tubers look shriveled in January?
If your tubers look wrinkled like a raisin, they are losing too much moisture. You can easily remedy this by lightly misting the packing material (like peat moss or wood shavings) with a spray bottle of water. Avoid soaking them; you just want to increase the ambient humidity in the storage container so the tubers can rehydrate slightly.
Do I have to wash the dirt off the tubers before storing them?
Washing is not strictly required, but it is often helpful. Removing the dirt allows you to clearly see the "eyes" for dividing and helps you spot any hidden damage or signs of rot. If you choose not to wash them, ensure you brush off as much loose soil as possible, as soil can harbor fungi and bacteria that may lead to problems during the long winter months.
