Introduction
There is a unique sense of satisfaction that comes with digging up your dahlia tubers at the end of a successful growing season. After months of enjoying those spectacular dinnerplate dahlias and vibrant colors, the prospect of saving those same plants for next year feels like a rewarding gift to your future self. At Longfield Gardens, we believe that overwintering your dahlias is one of the best ways to expand your garden and ensure your favorite varieties return even stronger the following summer.
One of the most common questions we receive from home gardeners is how to properly pack these tubers to keep them healthy through the cold months. While there are several materials you can use, How to Lift and Store Dahlia Bulbs is a helpful companion guide, and sawdust and wood shavings are popular choices for a reason. This guide will help you understand the benefits of using sawdust, how to choose the right type, and the best way to pack your tubers for a successful winter nap.
Whether you are a seasoned dahlia enthusiast or a beginner looking to save your first clump of tubers, understanding the "how" and "why" of storage media will give you the confidence you need. Using the right materials and techniques ensures your dahlias stay plump, hydrated, and ready to sprout as soon as the spring sun warms the soil. By following a few simple steps, you can turn a single season of beauty into a lifetime of garden joy with our dahlia collections.
Why Use Sawdust for Storing Dahlia Tubers?
When it comes to choosing a storage medium for dahlia tubers, the goal is to find a material that strikes a perfect balance. It needs to insulate the tubers from temperature swings, provide enough moisture to keep them from shriveling, and allow for enough air circulation to prevent rot. Sawdust and wood shavings have become a go-to for many gardeners because they meet these criteria beautifully while being lightweight and easy to handle.
Natural Insulation and Moisture Control
Sawdust acts as a natural insulator. In a basement or garage where temperatures might fluctuate, a thick layer of sawdust helps keep the tubers at a steady temperature. This stability is vital because it prevents the tubers from "waking up" too early if there is a mid-winter warm spell.
Furthermore, sawdust has a natural ability to manage humidity. It can absorb excess moisture that might otherwise lead to mold, but it also holds onto enough ambient humidity to prevent the tubers from drying out completely. This "Goldilocks" effect—not too wet and not too dry—is exactly what a dormant dahlia tuber needs to survive until spring.
Portability and Ease of Use
One of the most practical reasons to choose sawdust or wood shavings is their weight. If you have a large collection of dahlias, storing them in heavy soil or damp sand can make the storage bins incredibly difficult to move. Sawdust is light as a feather, making it much easier to carry bins down into a basement or up onto a garage shelf.
Additionally, sawdust is generally quite affordable and easy to find. Many gardeners can source it from local woodshops, or they can purchase bags of kiln-dried wood shavings from pet supply stores. Because it is a natural byproduct, it is also an environmentally friendly choice that can be repurposed in the garden once the tubers are unpacked in the spring.
Cleanliness and Reusability
Unlike peat moss, which can be dusty and messy to work with indoors, sawdust tends to stay in place once it is packed into a bin. When spring arrives and it is time to plant, the sawdust can be shaken off the tubers easily. You can then take that used sawdust and add it to your compost pile or use it as a light mulch around your perennials. This makes the entire process efficient and waste-free.
Key Takeaway: Sawdust is an excellent storage medium because it is lightweight, provides natural temperature insulation, and helps maintain the ideal moisture balance for dormant tubers.
Choosing the Right Type of Sawdust
Not all wood products are created equal when it comes to plant storage. Before you head to the local sawmill or pet store, it is important to know which types of sawdust will help your dahlias thrive and which might cause issues.
Wood Shavings vs. Fine Sawdust
In the gardening world, the terms "sawdust" and "wood shavings" are often used interchangeably, but there is a slight difference. Fine sawdust is the powdery material left behind by a saw. Wood shavings are larger, flatter pieces typically produced by a planer or found in pet bedding.
For dahlia storage, wood shavings are often the superior choice. The larger size of the shavings allows for better air pockets within the storage container. This increased air circulation is a great defense against rot. Fine sawdust can sometimes pack down too tightly, especially if it gets damp, which can suffocate the tubers or trap too much moisture against their skin. If you only have access to fine sawdust, just be sure not to pack it down firmly; keep it loose and fluffy.
Recommended Wood Species
Pine and aspen are the most recommended types of wood for dahlia storage. These woods are generally neutral and do not contain high levels of oils or tannins that could irritate the tubers. Kiln-dried pine shavings, often sold as bedding for small animals, are particularly effective because they are clean, consistent, and free of pests or weed seeds.
It is best to avoid cedar sawdust or shavings. While cedar smells wonderful and naturally repels insects, it contains strong aromatic oils that can be a bit too aggressive for the thin skin of a dahlia tuber. Some gardeners have found that cedar can inhibit the growth of the tubers or cause minor damage during the long months of storage.
Avoiding Treated Wood
This is perhaps the most important rule: never use sawdust or shavings from pressure-treated lumber, plywood, or particle board. These products contain glues, resins, and chemicals designed to prevent wood from decaying. Those same chemicals can be toxic to your dahlia tubers and may leach into the soil when you eventually plant them. Always stick to natural, untreated wood sources to keep your garden safe and healthy.
Preparing Your Tubers for the Sawdust Lasagna
Before you can pack your tubers away in sawdust, they need a little bit of preparation. Taking the time to properly dig and cure your dahlias will ensure they are in the best possible condition for their winter rest.
The Waiting Game: Frost and Dormancy
In most regions, the signal to dig your dahlias is the first "killing frost." This is when the temperatures drop enough to turn the green foliage of the plant black or brown. While it might look a bit sad, this is actually a vital part of the plant's life cycle. The frost tells the dahlia to stop growing and send all its energy down into the tubers for the winter.
After the first frost, we recommend waiting about 5 to 10 days before digging. When to Lift Dahlia Bulbs explains why that short waiting period helps the tubers cure and toughen their skin. If your weather is turning extremely cold or very wet, you can dig them sooner, but that extra week in the ground is a helpful bonus for the plant.
Digging and Cleaning
When it is time to dig, use a garden fork rather than a shovel. Start your digging about 12 inches away from the main stem to avoid accidentally slicing through the tubers. Gently lift the entire clump out of the ground.
Once the clump is out, you have a choice: you can wash the soil off with a gentle stream of water from a hose, or you can simply brush off the loose dirt with your hands. If you choose to wash them, make sure they have plenty of time to dry completely before you pack them away. Packing wet tubers into sawdust is a recipe for mold.
Curing the Tubers
After cleaning, place your tubers in a cool, dry area out of direct sunlight for about 24 to 48 hours. This allows any remaining surface moisture to evaporate and helps any small nicks or cuts on the tubers to callously over. A garage or a covered porch is usually a great spot for this. You want the tubers to feel dry to the touch, but you don't want them to stay out so long that they begin to look wrinkled or shriveled.
What to do next:
- Cut the stalks down to about 2–4 inches above the tuber clump.
- Gently lift the tubers with a garden fork, working in a wide circle.
- Brush off excess soil or rinse gently and allow them to dry for 1–2 days.
- Label each clump with its variety name using a permanent marker or a tag.
The Packing Process: Step-by-Step
Packing dahlias in sawdust is often referred to as the "lasagna method" because it involves alternating layers of storage medium and tubers. This ensures that every tuber is protected and insulated.
Step 1: Choose Your Container
You can use plastic totes, cardboard boxes, or even wooden crates.
- Plastic Totes: These are excellent for drier environments (like modern homes with central heating) because they hold onto moisture well. However, you should leave the lid slightly ajar or drill a few small air holes in the sides to prevent condensation from building up.
- Cardboard Boxes: These are better for damp basements because the cardboard can breathe and absorb a bit of excess humidity.
Step 2: The Bottom Layer
Start by pouring about 2 to 3 inches of sawdust or wood shavings into the bottom of your container. Level it out with your hand so you have a soft, even base. This layer prevents the tubers from touching the bottom of the bin, which can sometimes get cold or collect moisture.
Step 3: Arranging the Tubers
Place your dahlia tubers on top of the sawdust. The most important rule here is to make sure the tubers are not touching each other. If one tuber happens to develop a spot of rot during the winter, the sawdust will act as a barrier to keep that rot from spreading to its neighbors. If they are touching, the rot can move quickly through the whole bin.
Step 4: Adding the Filling
Pour more sawdust over the tubers until they are completely covered. Gently jiggle or tap the sides of the bin to help the sawdust settle into all the nooks and crannies between the tubers. You want to eliminate large air pockets, as these can cause the tubers to dry out faster.
Step 5: Repeat
If your container is deep enough, you can add another layer of tubers and another layer of sawdust. Always finish with a final 2-to-3-inch layer of sawdust on the very top to act as a protective "blanket."
Maintaining the Ideal Storage Environment
Once your dahlias are packed away, the location where you store the bins is just as important as the material you used to pack them. Dahlias are like Goldilocks—they need conditions that are "just right" to stay dormant without dying.
The Sweet Spot for Temperature
The ideal temperature for storing dahlia tubers is between 40°F and 45°F (4°C to 7°C).
- Too Cold: If the temperature drops below freezing (32°F), the water inside the tubers will freeze, causing the cell walls to burst. When they thaw, the tubers will turn into a mushy, black mess that cannot be saved.
- Too Warm: If the temperature stays above 50°F for too long, the tubers may think it is spring and begin to grow sprouts in the dark. This uses up the tuber's stored energy and can result in a weaker plant once it is finally put in the ground.
Unheated basements, crawl spaces, and insulated garages are usually the best spots. If you store them in a garage, make sure the bins are moved away from the door and perhaps wrapped in an old blanket for extra protection during extreme cold snaps. If you need a regional reference, the Hardiness Zone Map is a useful place to start.
Monitoring Humidity and Moisture
Dahlias prefer a humidity level of around 80% to 90%. This sounds high, but it is typical for a cool basement. The sawdust will do a lot of the work for you, but it is still a good idea to check on your "investments" once a month.
Open your bins and feel a few of the tubers.
- If they feel plump and firm: Everything is going perfectly. Close the bin and check again in a month.
- If they look wrinkled or feel slightly soft: The environment is too dry. You can use a spray bottle to lightly mist the surface of the sawdust. Don't soak it; just a few sprays of water will add enough moisture back into the air.
- If you see fuzzy mold or soft, dark spots: The environment is too wet. Remove any rotting tubers immediately. Leave the lid off the container for a few days to let the sawdust dry out, and consider moving the bin to a spot with better air circulation.
Key Takeaway: Successful storage depends on a consistent temperature of 40–45°F and a monthly check-in to ensure the tubers are neither shriveling from dryness nor rotting from excess moisture.
To Divide or Not to Divide?
One of the big debates in the gardening community is whether to divide your dahlia clumps in the fall before you pack them in sawdust, or in the spring before you plant them. Both methods have their fans, and the choice often depends on your schedule and your storage space.
Dividing in the Fall
Many gardeners prefer to divide their clumps in the fall. When the tubers are fresh out of the ground, they are softer and easier to cut. Dividing now also saves a significant amount of storage space; instead of storing a bulky clump the size of a basketball, you are storing individual tubers.
The challenge with fall division is that it can be harder to see the "eyes"—the small bumps where next year's stems will grow. If you divide in the fall, you must be careful to ensure each individual tuber has a piece of the main crown (the neck) and at least one viable eye.
Dividing in the Spring
At Longfield Gardens, we often find that leaving the clumps whole over the winter is a great strategy for beginners. For more growing basics, see How to Grow Great Dahlias. The outer tubers in a clump help protect the inner ones from drying out. Furthermore, by spring, the "eyes" will have begun to swell and may even have tiny green sprouts, making it incredibly easy to see exactly where to make your cuts.
The only downside to spring division is that the tubers become much tougher and more "leathery" over the winter, requiring a very sharp knife and a bit more elbow grease to separate. If you have plenty of sawdust and enough room in your basement, leaving them whole is a very safe bet.
Common Myths About Sawdust Storage
When researching how to store dahlias, you might come across some conflicting advice. Let's clear up a few common misconceptions about using sawdust.
"Sawdust will make my soil too acidic."
While it is true that wood is naturally acidic, the small amount of sawdust that clings to your tubers when you plant them in the spring will have a negligible effect on your soil's pH. If you are worried, simply shake or brush the tubers clean before they go into the ground.
"Sawdust attracts pests."
As long as you are using clean, dry wood shavings or sawdust, it shouldn't attract any more pests than any other organic material. In fact, many gardeners find that sawdust is less attractive to mice than materials like straw. To be safe, always keep your storage bins in a clean area and ensure plastic lids are snapped on (but vented).
"You have to use fresh sawdust every year."
You can actually reuse your sawdust for several seasons as long as it stays dry and hasn't been in contact with rotting tubers. If you had a bin that suffered from significant rot, it is best to compost that sawdust and start fresh the following year to avoid carrying over any fungal spores.
Realistic Expectations for Overwintering
It is important to remember that gardening is a partnership with nature, and nature can be unpredictable. Even with the best sawdust and the most careful packing, it is normal to lose a small percentage of tubers over the winter. Some varieties are simply better "keepers" than others.
Factors like the health of the plant during the summer, the amount of rain you had in the weeks before harvest, and the specific microclimate of your storage area all play a role. Don't be discouraged if a few tubers don't make it. Instead, focus on the ones that do. Often, a single healthy clump will produce so many new tubers when divided that you will still end up with more plants than you started with!
We always recommend trying a couple of different storage spots or methods if you are new to the process. You might put one bin in the crawl space and one in the garage. By spring, you'll know which "neighborhood" your dahlias prefer.
Using Sawdust as a Sustainable Garden Tool
One of the reasons we love sawdust at Longfield Gardens is its versatility. Once your dahlias are safely in the ground and the danger of frost has passed, you are left with a bin of material that is still useful.
If you used pine or aspen shavings, you can spread them around the base of your newly planted dahlias or other perennials. As the wood breaks down, it improves the soil structure and encourages healthy fungal activity. This is a great way to close the loop in your garden cycle. For next-season color ideas, browse our Shop by Color - Spring-Planted Bulbs.
If you prefer a tidy look in your flower beds, simply toss the used sawdust into your compost bin. It provides the "brown" (carbon-rich) material that balances out the "green" (nitrogen-rich) kitchen scraps and grass clippings. It is a win-win for your garden's health.
Conclusion
Storing dahlia tubers in sawdust is an effective, accessible, and rewarding way to preserve your garden's beauty from one year to the next. By selecting the right type of wood—ideally kiln-dried pine or aspen shavings—and following the "lasagna" layering method, you provide your tubers with the insulation and moisture control they need to stay healthy all winter long.
Remember that the keys to success are simple: dig after the frost, cure the tubers so they are dry to the touch, and keep them in a cool, dark place where they won't freeze. A quick monthly check-in is all it takes to ensure your dahlias are ready for their spring debut.
- Wait for a killing frost to trigger dormancy before digging.
- Use wood shavings for better air circulation than fine dust.
- Keep tubers from touching inside the storage bins.
- Aim for 40-45°F in your storage area.
We hope this guide makes the process feel straightforward and achievable. There is nothing quite like the feeling of planting a tuber you saved yourself and watching it grow into a magnificent floral display. If you're looking to add new colors or shapes to your collection, we invite you to explore the Dahlia Assorted Sunlit Jewel Collection at Longfield Gardens. Happy gardening, and enjoy the satisfaction of a job well done.
Overwintering your dahlias is more than just a chores—it is an investment in a more beautiful, abundant garden for the seasons to come. If you're looking to add another rich mix for next spring, the Dahlia Assorted Harvest Collection is another beautiful place to start.
FAQ
Can I use sawdust from a local sawmill for my dahlias?
Yes, you can use sawdust from a local mill as long as you are certain it comes from untreated wood like pine, oak, or maple. Avoid any sawdust that might contain walnut wood, as walnut contains a natural chemical called juglone that can be toxic to many other plants. Also, ensure the sawdust is dry before using it, as "green" or fresh-cut sawdust often holds too much moisture.
Should the sawdust be wet or dry when I pack the tubers?
The sawdust should be mostly dry or very slightly damp to the touch—similar to the consistency of a wrung-out sponge. If the sawdust is bone-dry, it might suck too much moisture out of the tubers. If it is visibly wet, it will cause the tubers to rot. Most gardeners find that "bagged" shavings from the store have the perfect moisture level right out of the bag.
Is it okay to use cedar shavings for dahlia storage?
While some gardeners use cedar without issues, it is generally not the first choice. Cedar contains high levels of aromatic oils that can sometimes irritate the surface of the tubers or inhibit their growth. Pine or aspen shavings are safer, more neutral alternatives that provide all the same benefits without the risk of aromatic oil sensitivity.
How often should I check my tubers stored in sawdust?
A good rule of thumb is to check your tubers once a month. This allows you to catch any issues early. If you see shriveling, you can lightly mist the sawdust with water. If you see mold or soft spots, you can remove the affected tubers and increase air circulation. Regular check-ins are the best way to ensure a high survival rate for your dahlia collection.
