Table of Contents
- Introduction
- Understanding the Dahlia Lifecycle
- Should I Dig or Leave Them?
- Identifying the Right Time to Dig
- Step-by-Step Guide to Digging Your Dahlias
- Proper Curing for Storage Success
- Choosing Your Storage Medium
- Where to Keep Your Tubers Over Winter
- Mid-Winter Check-Ups
- Common Myths About Digging Dahlias
- Planning for the Spring
- Conclusion
- FAQ
Introduction
There is nothing quite like the peak of summer when dahlias are in full swing. These garden superstars produce some of the most spectacular blooms you can grow. From the massive, pillowy petals of dinnerplate varieties to the intricate patterns of pompons, they offer a color for every palate. At Longfield Gardens, we know how much joy these flowers bring to your outdoor space. They turn a simple garden bed into a vibrant sanctuary that provides endless bouquets for your home.
As the season winds down and the first crisp nights of autumn arrive, you might wonder about the future of your plants. Dahlias are tender perennials. This means they are not naturally equipped to survive freezing temperatures in most parts of the United States. While they are often called "bulbs" by home gardeners, they actually grow from underground structures called tubers. Whether you should dig them up or leave them in the ground is one of the most common questions we receive.
The answer depends on where you live and the type of soil in your garden. This guide will help you determine the best path for your plants. We will cover how to identify your hardiness zone and the simple steps for lifting and storing your tubers. By following a few easy rules, you can keep your favorite varieties healthy and ready to bloom again next year.
Understanding the Dahlia Lifecycle
Dahlias are native to the high plains of Mexico and Central America. In their natural habitat, they enjoy warm days and cool, frost-free nights. Because they did not evolve to withstand deep freezes, their tubers are full of moisture. When the ground freezes, that moisture expands and turns the tuber into a soft, unusable mass.
In the United States, we use USDA Plant Hardiness Zones to determine which plants can survive the winter outdoors. Most dahlias are only hardy in Zones 8 through 11. In these warmer regions, the ground rarely freezes deep enough to reach the tubers. If you live in a colder area, specifically Zones 3 through 7, digging them up is usually the only way to ensure they return.
The timing of this process is just as important as the method. You want to give the plant as much time as possible to store energy. Throughout the summer and early fall, the foliage is busy photosynthesizing. This process creates sugars that are stored in the tubers. This stored energy is what fuels the first push of growth the following spring. Cutting the plants back too early can result in smaller, weaker tubers that are harder to store.
Should I Dig or Leave Them?
The decision to dig up your dahlias usually comes down to your local climate. However, there are a few other factors to consider, such as your well-drained soil and your desire to expand your garden.
When to Leave Them in the Ground
If you live in USDA Zone 8 or higher, you are likely in a "safe zone." In places like Georgia, Texas, or coastal California, dahlias can often stay in the ground all year. The primary risk in these areas isn't usually the cold, but rather moisture. Dahlias hate sitting in cold, soggy soil. If your garden has excellent drainage and your winters are relatively dry, leaving them in place is a great time-saving option.
Even in these warmer zones, we suggest adding a thick layer of mulch. A 4- to 6-inch layer of straw, wood chips, or shredded leaves acts as a blanket. It regulates the soil temperature and prevents the crown of the plant from being exposed to occasional light frosts.
When Digging is Necessary
For gardeners in Zones 3 through 7, digging is a standard part of the fall routine. In these regions, the ground will freeze several inches deep. This will inevitably destroy the tubers if they are left unprotected. While some gardeners in Zone 7 try to "overwinter" them with heavy mulching, it is often a gamble. A particularly wet or unusually cold winter can result in the loss of your favorite plants.
Digging also gives you the chance to divide your tubers. A single dahlia tuber planted in the spring can grow into a large clump by October. If you leave that clump in the ground for years, it can become overcrowded. This leads to smaller flowers and weaker stems. Lifting the tubers allows you to separate them, giving you more plants to fill your garden or share with friends.
Key Takeaway: If you live in Zone 7 or colder, digging up your dahlia tubers is the most reliable way to ensure they survive the winter. In warmer zones, you can often leave them if your soil drains well.
Identifying the Right Time to Dig
The most common signal to start digging is the weather. Most gardeners wait for the first "killing frost." This is a frost that is cold enough to turn the green dahlia foliage black or dark brown. This usually happens when temperatures dip below 32°F for several hours.
While the black foliage might look a bit sad, it is actually a helpful sign. It tells the plant to stop sending energy to the leaves and start focusing on dormancy. We recommend waiting about a week or two after this first frost before you start digging. This short waiting period allows the "eyes" on the tubers to become more prominent. The eyes are the small bumps where next year's growth will emerge. Being able to see them makes it much easier if you plan to divide the clumps later.
If you live in an area that stays quite warm and you don't get a frost until very late in the year, you can still dig them up. Once the days get short and the temperatures stay consistently in the 40s or 50s, the plants will naturally begin to slow down. You can safely lift them at this point, even if the leaves are still green.
Step-by-Step Guide to Digging Your Dahlias
Digging up tubers is a straightforward process, but it requires a gentle touch. Unlike potatoes, dahlia tubers have a "neck" that connects the tuber to the main stem. If this neck is broken or cracked, the tuber will likely not grow in the spring.
Step 1: Cut Back the Stems
Start by cutting the stalks down to about 4 to 6 inches above the soil line. You can use pruners or a small garden saw for thicker stems. Removing the bulk of the plant makes it much easier to see where you are working. The remaining few inches of stem act as a handle and help you keep track of where the center of the clump is located.
Step 2: Loosen the Soil
It is best to use a garden fork (also called a pitchfork) rather than a shovel. A shovel has a sharp, solid blade that can easily slice through a hidden tuber. A fork allows you to gently pry the soil upward.
Start your digging about 12 inches away from the main stem. Insert the fork deep into the ground and gently rock it back and forth. Move in a circle around the plant, loosening the soil on all sides. This ensures you aren't tugging against roots that are still firmly anchored.
Step 3: Lift the Clump
Once the soil is loose, slide the fork underneath the clump and lift it gently. Avoid pulling on the stem handle with too much force. Let the fork do the heavy lifting. Once the clump is out of the ground, shake it gently to remove large chunks of soil.
Step 4: Clean and Inspect
You have two choices here: you can either wash the tubers with a garden hose or simply brush off the dry dirt. Washing makes it much easier to see the eyes and check for any signs of rot or insect damage. However, if you wash them, you must be very careful to let them dry completely before storage.
While cleaning, look for any tubers that feel soft, mushy, or hollow. Use a clean, sharp knife to trim away any damaged parts. If a tuber is hanging by a thread or has a broken neck, it is best to remove it now, as it likely won't survive the winter anyway.
What to Do Next
- Label each clump immediately using a waterproof marker or a nursery tag.
- Turn the clumps upside down for a few hours to allow any water trapped in the hollow stems to drain out.
- Move the tubers to a shaded, frost-free area like a porch or garage.
- Let them "cure" (dry out) for 1 to 3 days until the skin feels firm and the surface moisture is gone.
Proper Curing for Storage Success
Curing is a vital step that many beginners skip. This process allows the outer skin of the tuber to toughen up slightly. It also ensures that the "handle" or stem you left behind has a chance to dry out. If you put wet, freshly dug tubers directly into a sealed container, they are very likely to rot within a few weeks.
Choose a spot with good air circulation but keep them out of direct sunlight. Sunlight can cause the tubers to shrivel or try to "wake up" prematurely. A basement floor or a shelf in a cool garage is perfect. We often use mesh trays or old window screens to cure our tubers at Longfield Gardens. This allows air to reach the bottom of the clump as well as the top.
Once the tubers are dry to the touch and any remaining soil has turned to dust, they are ready for their winter home. Do not leave them out for more than a few days, or they may lose too much moisture and become shriveled like a raisin.
Choosing Your Storage Medium
The goal of winter storage is to keep the tubers dormant, cool, and slightly hydrated. You want to prevent them from rotting (too wet) and prevent them from shriveling (too dry). To achieve this balance, most gardeners use a storage medium.
Popular Storage Options
- Vermiculite: This is a favorite for many professional growers. It is lightweight, sterile, and does an excellent job of regulating moisture.
- Peat Moss: This is an affordable and widely available option. It stays dry but provides enough insulation to prevent total dehydration.
- Wood Shavings: Common "fine" animal bedding works well. It allows for great air circulation.
- Newspaper or Cardboard: Some gardeners simply wrap individual tubers in several layers of newspaper and tuck them into a box.
Container Types
You can store your tubers in plastic bins, cardboard boxes, or even paper bags. If you use plastic bins, do not snap the lid on tight. Leave it cracked an inch or two to allow gases and excess moisture to escape. Cardboard boxes are naturally breathable and are an excellent choice for basement storage.
Place a layer of your chosen medium in the bottom of the container. Lay the tubers in a single layer, making sure they aren't touching each other. Cover them with more medium and repeat the process if your box is deep. This "nesting" approach prevents a single rotten tuber from spreading mold to its neighbors.
Key Takeaway: The perfect storage environment is cool (40-50°F), dark, and has just enough moisture to keep the tubers firm but not wet.
Where to Keep Your Tubers Over Winter
Finding the right location in your home is often the hardest part of the process. You are looking for a spot that stays consistently between 40°F and 50°F. If you need more storage details, see How to Overwinter Dahlias.
The Unheated Basement
This is often the gold standard. Most basements stay cool and relatively humid. Avoid placing your boxes near the furnace or water heater, as the heat will dry out the tubers or cause them to sprout in January.
The Attached Garage
If your garage is insulated and doesn't drop below freezing, it can be a good spot. However, keep a thermometer in there. If the temperature hits 32°F, your dahlias will turn to mush. We suggest keeping the boxes off the cold concrete floor by placing them on a wooden pallet or a shelf.
A Cool Closet
In modern, well-insulated homes, finding a 40°F room can be tough. A closet on an outside wall or a crawl space can sometimes work. Just be sure to check the temperature periodically. If the space is too warm (above 55°F), the tubers will think it is spring and start growing long, pale sprouts.
Mid-Winter Check-Ups
Gardening doesn't entirely stop in the winter. It is a good habit to check on your stored dahlias once a month. This small effort can save your entire collection.
When you open your boxes, look for two things:
- Signs of Rot: If a tuber feels soft or smells bad, remove it immediately. Cut off any fuzzy mold and let the remaining tubers get some fresh air for an hour before re-packing them.
- Signs of Shriveling: If the tubers look wrinkled and feel light, they are too dry. Use a spray bottle to lightly mist the storage medium. You don't want it to be wet, just slightly damp to the touch.
If you see small sprouts starting to form in late winter, don't panic. This is normal as the days get longer. Simply keep the tubers in the dark and as cool as possible to slow down the growth until it is time to plant.
Common Myths About Digging Dahlias
There is a lot of conflicting advice online about dahlia care. Let's clear up a few common misconceptions to make your gardening life easier.
Myth 1: You must wash every tuber with bleach. While some growers use a very diluted bleach solution to kill bacteria, it isn't necessary for most home gardeners. As long as you remove any rotten parts and keep the tubers dry during curing, they should be fine. Simple clean water is enough.
Myth 2: You have to divide the clumps in the fall. You can certainly wait until spring to divide your dahlias. In fact, for beginners, spring is often better because the eyes are much easier to see once they start to swell. Storing the whole clump is perfectly fine, though it does take up more space.
Myth 3: If a tuber shrivels, it's dead. Not necessarily! A slightly wrinkled tuber can often be revived by soaking it in a bucket of room-temperature water for a few hours just before planting in the spring. As long as the neck is intact and there is at least one healthy eye, the plant has a good chance of growing.
Planning for the Spring
As the winter begins to fade, you can start looking forward to planting time. Dahlias are sensitive to cold soil. We recommend waiting until the soil temperature reaches about 60°F before putting them back in the ground. This usually aligns with the time you would plant tomatoes or peppers in your region.
About two to three weeks before your last frost date, you can bring your tubers out of storage and into a warmer room. This "wakes them up" and encourages the eyes to start sprouting. If you are eager for early blooms, you can even start them in pots indoors and transplant them once the weather is settled.
One of the great joys of our work at Longfield Gardens is seeing our trial gardens burst into life each year. We test many different varieties to see how they handle storage and regrowth. This ensures that the advice we give you is rooted in practical experience. Dahlias are incredibly resilient plants. Even if you make a small mistake in your storage process, they often find a way to thrive.
Conclusion
Digging up your dahlia tubers—or more accurately, their tubers—is a simple and rewarding part of the gardening cycle. While it might seem like a lot of work at first, it quickly becomes a rhythmic end-of-season tradition. By understanding your USDA zone and providing a cool, dry winter home for your plants, you can enjoy the same beautiful blooms year after year.
At Longfield Gardens, we believe that gardening should be a source of relaxation and pride. Saving your own tubers is not only economical but also gives you a deeper connection to your garden's history. Each spring, as you tuck those tubers back into the warm earth, you are continuing a beautiful story that started the summer before.
- Determine if your zone requires digging (Zone 7 and colder).
- Wait for the first frost to turn foliage brown before lifting.
- Dig carefully with a fork to protect the fragile tuber necks.
- Cure for 1-3 days and store in a cool, dark place with a medium like vermiculite.
Every dahlia tuber you save is a head start on next year's most beautiful garden. We stand behind the 100% Quality Guarantee and are here to help you succeed in every season.
FAQ
Can I leave my dahlias in the ground if I live in Zone 7?
You can try, but it is a risk. In Zone 7, a heavy mulch of 6 inches may protect the tubers if the winter is mild and the soil is well-drained. However, a deep freeze or a very wet winter often leads to rot. For your most prized varieties, we recommend digging them up to be safe.
Do I need to wash the dirt off the tubers before storing them?
It is not strictly necessary, but it is helpful. Washing the tubers allows you to see the "eyes" more clearly and helps you spot any hidden rot or insect damage. If you choose not to wash them, just make sure to shake off the excess soil and let them dry thoroughly before putting them in a box.
What is the best temperature for storing dahlia tubers?
The ideal temperature range is between 40°F and 50°F. If the temperature stays above 55°F, the tubers may begin to sprout too early or dry out. If the temperature drops below 32°F, the moisture inside the tubers will freeze, causing them to rot and die.
Why did my dahlia tubers turn to mush in storage?
Mushy tubers are usually a sign of rot caused by too much moisture or freezing temperatures. This often happens if the tubers weren't dried (cured) enough before storage, if the storage container didn't have enough air circulation, or if the storage area got too cold. Always check your tubers monthly and remove any that show signs of decay. If you need help with an order or a plant issue, Contact Us.