Table of Contents
- Introduction
- When to Dig Up Dahlia Tubers
- Preparing the Plants for Digging
- How to Dig Up Dahlia Tubers Safely
- Cleaning and Curing the Tubers
- To Divide or Not to Divide?
- Understanding Tuber Anatomy
- How to Divide Dahlia Tubers Step-by-Step
- Choosing the Right Storage Medium
- The Ideal Storage Environment
- Winter Maintenance and Monitoring
- Preparing for Spring
- Conclusion
- FAQ
Introduction
There is nothing quite like the sight of a dahlia garden in peak late-summer bloom. These plants provide a spectacular finale to the growing season with their vibrant colors and intricate shapes. Whether you grew massive dinnerplate varieties or charming pompons, the transition into fall doesn't have to mean saying goodbye to your favorite flowers. Learning how to dig up and store dahlia tubers is one of the most rewarding skills a gardener can master. It allows you to save your favorite plants, increase your stock for free, and enjoy a bigger display every year.
At Longfield Gardens, we want every gardener to feel confident in preserving their plants over the winter months. Digging and storing tubers might seem like a complex task reserved for professionals, but it is actually a straightforward process that fits easily into a weekend afternoon. By following a few simple steps, you can ensure your plants remain healthy and dormant until it is time to plant them again in the spring.
This guide will walk you through the entire journey of overwintering your dahlias. We will cover the best timing for digging, the gentlest ways to lift the tubers, and the most effective storage methods for different home environments. This article is designed for home gardeners who want clear, practical advice to protect their floral investment. Mastering this process turns gardening into a sustainable, multi-year cycle of beauty.
When to Dig Up Dahlia Tubers
Timing is everything when it comes to successfully overwintering dahlias. While it might be tempting to start cleaning up the garden as soon as the weather turns chilly, patience is a virtue here. The tubers need time to mature and store the energy required to sprout next season.
The Role of the First Frost
For most gardeners in the United States, the first killing frost is the most reliable signal to begin. A killing frost is one that turns the dahlia foliage black or dark brown. When this happens, the plant stops sending energy to the leaves and begins to go dormant.
Wait about a week after this first frost before you start digging. This brief waiting period allows the tubers to "cure" slightly in the ground. During these few days, the eyes (the small bumps where next year’s growth will emerge) often become more prominent. This makes the job of dividing much easier later on.
Counting the Days
If you live in a region where frosts are rare or very late, you can use the calendar instead. Most dahlias need about 120 to 150 days of growth to produce mature, viable tubers. If your plants have been in the ground for at least four months, the tubers should be ready for storage. You can safely dig them up by mid-November even if a frost has not yet occurred.
Why Soil Temperature Matters
It is important to get the tubers out of the ground before the soil itself freezes. While the foliage can handle a light frost, the tubers are high in water content. If the ground freezes solid, the water inside the tubers will expand and destroy the plant tissue. This results in mushy, unusable roots. Aim for a window of time when the air is cold but the soil is still workable and hasn't reached freezing temperatures.
Preparing the Plants for Digging
Before you reach for your shovel, there are a few preparation steps that make the process much smoother. Proper preparation protects the fragile tubers and ensures you don't lose track of which variety is which.
Cutting Back the Foliage
Once the plants have been hit by frost and you have waited a few days, it is time to clear the top growth. Use a sharp pair of bypass pruners or loppers to cut the main stalks. You should leave about 4 to 6 inches of stem protruding from the ground.
This leftover stem serves as a "handle" for the tuber clump. It makes the clump easier to lift and helps you identify the center of the root system. Do not cut the stems flush with the ground, as this makes it much harder to locate the tubers without accidentally stabbing them with your tools.
Labeling Your Varieties
Identification is the step most gardeners regret skipping. Once tubers are out of the ground and cleaned, they all look remarkably similar. If you have several varieties, such as the classic Thomas Edison, you will want to know which is which come spring.
The creamy Cafe au Lait is another one worth labeling carefully.
Attach a waterproof tag or label directly to the 6-inch stem handle. You can use plastic garden labels secured with a twist tie or even write the name directly on the tuber later with a permanent marker. Consistency at this stage ensures your garden design stays on track next year.
What to do next:
- Check your local weather forecast for the first expected frost.
- Gather your labels and a permanent marker.
- Ensure your pruners are sharp and clean.
How to Dig Up Dahlia Tubers Safely
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 breaks, the tuber may not be able to sprout. Using the right technique is essential to keeping the clump intact.
Choose the Right Tools
A sturdy garden fork is often better than a shovel for this task. The tines of a fork allow soil to fall through, making it easier to lift the weight of the clump. If you only have a shovel, ensure it is sharp and used with extra care.
The Lifting Technique
Start by standing about 12 inches away from the base of the stem. You want to avoid hitting the tubers that have grown outward during the summer. Push your fork deep into the soil and gently pry upward.
Work your way around the entire plant in a circle, loosening the soil from all sides. Once the soil is loose, place one hand on the stem handle and use the fork to gently lift the entire clump out of the ground. Avoid the temptation to yank the plant up by the stem, as this is the most common way to break the fragile necks.
Initial Cleaning
Once the clump is out of the ground, gently shake it to remove large clods of dirt. You can use a small stick or your gloved fingers to poke away excess soil from between the tubers. Do not worry about getting them perfectly clean yet; the goal at this stage is simply to lighten the load and see what you are working with.
Cleaning and Curing the Tubers
After digging, the tubers need a bit of "spa time" to prepare for their long winter nap. This involves removing the rest of the soil and allowing the outer skin to toughen up.
Washing the Clumps
Many gardeners find that a gentle spray from a garden hose is the easiest way to remove remaining soil. Use a medium pressure setting—enough to move the dirt but not so much that it peels the skin off the tubers. Washing is important because soil can harbor fungi or pests that might cause rot during storage.
If your soil is very sandy, you might be able to simply brush the dirt off once it dries. However, if you have heavy clay soil, washing is usually necessary to get into the nooks and crannies of the clump.
The Curing Process
Curing is the process of letting the tubers dry slightly before they go into containers. Place your cleaned clumps in a frost-free, shaded area with good air circulation. A garage, shed, or covered porch works well.
Do not leave tubers in direct sunlight, as this can cause them to overheat or dry out too fast. Let them sit for 1 to 3 days. You want the surface to feel dry to the touch and any remaining bits of soil to be crumbly. This drying period helps prevent mold and rot once the tubers are packed away.
Key Takeaway: Properly cleaned and cured tubers have a much higher survival rate. Removing soil and allowing the skin to dry prevents moisture-loving rot from taking hold during the winter months.
To Divide or Not to Divide?
One of the most common questions gardeners ask us is whether they should divide their dahlia clumps in the fall or wait until spring. Both methods have advantages, and the right choice depends on your space and experience level.
Storing Whole Clumps
Storing the entire clump as it came out of the ground is the easiest option for beginners.
- Pros: It is faster, and the tubers are less likely to dry out because they are protected by the mass of the clump.
- Cons: Whole clumps take up a lot of physical space. You will also have to divide them in the spring anyway, and the stems can become very hard and woody by then.
Dividing in the Fall
Many experienced gardeners prefer to divide their tubers into individual pieces before storing them.
- Pros: It takes up much less storage space. The stems are softer and easier to cut in the fall. You can also inspect each tuber and discard any that look unhealthy.
- Cons: Individual tubers are more prone to shriveling if the storage conditions are too dry. It can also be harder to see the "eyes" in the fall.
If you choose to divide now, remember that every 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 will never grow into a new plant.
Understanding Tuber Anatomy
Before you start cutting, it helps to know what you are looking at. A viable dahlia tuber is a bit like a potato. To grow, it needs a specific set of parts.
The Tuber Body
This is the fleshy part that stores food and energy. It can be long and skinny or round like a potato. As long as it is firm and attached to the crown, the shape doesn't matter much.
The Neck
The neck is the narrow bridge between the body and the crown. It is the most vulnerable part of the plant. If the neck is bent or broken, the connection is lost, and the tuber will likely rot.
The Crown and the Eye
The crown is the "head" of the tuber where it attaches to the old stalk. This is where the eyes are located. Eyes look like tiny, raised bumps or small pimples. Sometimes they are slightly pink or purple.
If you aren't sure if a tuber has an eye, it is often best to leave it attached to a larger piece of the crown or wait until spring when the eyes begin to swell and become more obvious.
How to Divide Dahlia Tubers Step-by-Step
If you have decided to divide your tubers this fall, follow these steps to ensure you get the most plants for next year.
- Sanitize your tools. Use a sharp knife or bypass pruners. Wipe the blades with rubbing alcohol or a 10% bleach solution between each clump to prevent the spread of garden diseases.
- Cut the clump in half. If the clump is very large, it helps to split the main stalk down the middle first. This gives you a better view of the individual tubers.
- Remove "mother" tubers. The original tuber you planted in the spring is often large, dark, and slightly wrinkly. These "mother" tubers often rot during winter storage, so it is usually best to cut them off and compost them.
- Trim the small stuff. Cut away any thin, spindly tubers that are smaller than a AA battery. These rarely have enough energy to survive the winter.
- Identify the eyes. Look for the small bumps on the crown. Carefully cut individual tubers away from the main stalk, ensuring each one has a piece of that crown tissue attached.
- Label immediately. Use a soft pencil or a permanent marker to write the variety name directly on the skin of the tuber. This is the most foolproof way to stay organized.
Choosing the Right Storage Medium
You cannot simply toss dahlia tubers into a box and hope for the best. They need a packing material that regulates moisture—keeping them dry enough to prevent rot but moist enough to prevent shriveling.
Vermiculite
Vermiculite is a favorite among professional growers. It is a naturally occurring mineral that has been heated until it expands into light, absorbent flakes. It does an excellent job of maintaining a steady humidity level. It is clean, easy to handle, and can often be reused for several years.
Pine Shavings or Wood Shavings
Commonly sold as animal bedding, pine shavings are an affordable and effective option. They provide good insulation and allow for air circulation. Avoid using cedar shavings, as the oils can sometimes be too harsh for the tender tubers.
Peat Moss or Coco Coir
These materials are widely available and hold moisture well. However, they can sometimes be too good at holding moisture. If you use peat moss, ensure it is only slightly damp—not wet. If it feels like a wrung-out sponge, it is too wet. It should feel almost dry to the touch.
The Plastic Wrap Method
Some gardeners have great success wrapping individual, cleaned tubers tightly in plastic kitchen wrap. This seals the moisture inside the tuber itself. This method takes more time upfront but eliminates the need for bulky bags of shavings or vermiculite. It also makes it easy to spot rot early, as you can see through the clear plastic.
The Ideal Storage Environment
The location where you store your dahlias is just as important as how you pack them. You are looking for a "Goldilocks" environment: not too hot, not too cold, and just the right amount of humidity.
Temperature is King
The ideal temperature for dahlia storage is between 40°F and 50°F.
- If it gets too cold: If the temperature drops below freezing, the tubers will turn to mush.
- If it gets too warm: If the temperature stays above 55°F, the tubers may think it is springtime and begin to sprout prematurely, or they may simply dry out and shrivel.
An unheated basement, a crawl space, or a cool corner of a garage that doesn't freeze are usually the best spots.
Managing Humidity
Dahlias prefer a humidity level of about 80% to 90%. Since most homes are much drier than this in the winter, the storage medium (like vermiculite) does the heavy lifting.
If you are storing in a very dry basement, you might want to use plastic bins with lids left slightly ajar. If your storage area is damp or prone to mold, cardboard boxes or paper bags are better because they allow the tubers to "breathe" more.
Winter Maintenance and Monitoring
Overwintering dahlias is not a "set it and forget it" task. To ensure the highest success rate, you should check on your tubers about once a month.
Checking for Rot
During your monthly check, look for any tubers that feel soft, slimy, or smell bad. This is a sign of rot. If you find a rotten tuber, remove it immediately and throw it in the trash. Rot can spread quickly to healthy neighbors, so being proactive saves the rest of your collection.
Dealing with Shriveling
If the tubers look wrinkled or feel light and hollow, they are losing too much moisture. This is a common issue in modern homes with central heating. To fix this, use a spray bottle to lightly mist the storage medium (the shavings or vermiculite) with water. You don't want it to be wet, just slightly humid. The tubers will often "plump" back up after a little moisture is introduced.
Dealing with Mold
If you see a light dusting of white surface mold, it usually means there isn't enough air circulation or the medium is too damp. Wipe the mold off with a cloth dipped in a weak bleach solution, let the tuber dry for an hour, and return it to storage in a slightly drier material or a more ventilated container.
Preparing for Spring
As the days get longer and the ground begins to thaw, your dahlias will start to wake up. This is an exciting time for any gardener.
Around late March or early April, move your storage containers to a slightly warmer spot. This "wakes up" the eyes. You will see the small bumps begin to enlarge and perhaps even turn green. Once the danger of frost has passed and the soil has warmed to about 60°F, you can plant your saved tubers back into the garden.
By saving your own tubers, you'll often find that you have more than you can possibly plant. This is a wonderful opportunity to share with neighbors or trade with friends for different colors and shapes.
Conclusion
Digging and storing dahlia tubers is a simple, satisfying way to extend the life of your garden. It takes the guesswork out of spring planning because you already know you have a collection of beautiful, healthy plants ready to go. While every winter brings different weather, following these basic steps for cleaning, curing, and cool storage will give your dahlias the best possible chance for a spectacular return.
At Longfield Gardens, our 100% Quality Guarantee reflects our belief that success in the garden comes from getting these few basics right. By protecting your tubers from the winter chill, you are setting the stage for a summer filled with incredible blooms. Whether you are saving a single heirloom variety or a massive collection, the effort is always worth the reward.
Final Action Plan:
- Dig tubers after the first frost, leaving a 4-6 inch handle.
- Clean and cure for 1-3 days in a cool, shaded spot.
- Store in a medium like vermiculite at 40-50°F.
- Check once a month for rot or shriveling.
We invite you to explore our other dahlia collections.
These planning guides can help you design the dahlia garden of your dreams for next season.
FAQ
Can I leave my dahlia tubers in the ground all winter?
This depends on your USDA hardiness zone. If you live in Zone 8 or warmer, you can often leave dahlias in the ground with a thick layer of mulch for protection. However, in Zone 7 and colder, the ground usually freezes deep enough to kill the tubers, so digging them up is necessary for survival.
What happens if I don't wait for a frost to dig them up?
You can dig them up before a frost, provided they have had at least 120 days of growth. The main reason many gardeners wait for frost is that it naturally triggers the plant to enter dormancy and often makes the "eyes" easier to see. If you dig too early in the summer, the tubers may be immature and might not store as well.
Do I have to wash the tubers before storing them?
While not strictly required, washing is highly recommended. Soil can carry bacteria, fungi, and pests like nematodes or crown gall. Cleaning the tubers allows you to inspect them thoroughly for damage or disease and ensures that you aren't bringing garden pests into your storage area.
My tubers are shriveled in mid-winter; are they dead?
Not necessarily! Some light shriveling is normal as the tubers lose moisture. If they are still firm when squeezed, they are likely fine. Simply mist your storage medium (vermiculite or shavings) with a little water to increase the humidity. If the tuber is as flat as a piece of paper and feels hollow, it may be too far gone to recover.