Introduction
There is nothing quite like the late-summer magic of a garden filled with dahlias. Whether you love the massive, honeycomb petals of dinnerplate dahlias or the cheerful, compact blooms of a pompon dahlia, these plants are the undisputed stars of the autumn landscape. At Longfield Gardens, we know that many gardeners feel a deep connection to their favorite varieties and want to see them return year after year.
Saving your tubers is a rewarding way to build your collection and ensure your most beloved flowers continue to brighten your yard. While dahlias are tender perennials that cannot survive freezing soil in most regions, the process of lifting and storing them is simpler than many people realize. This guide will walk you through every step of the process, from the first frost to the final storage box.
By following a few basic steps, you can keep your dahlia tubers healthy, hydrated, and ready to sprout when spring returns. This post covers when to dig, how to clean and cure your tubers, and the best ways to pack them for a long winter’s nap. Saving your tubers is an easy win that turns a single season of beauty into a lifetime of gardening joy.
Knowing When to Begin
The timing of your dahlia harvest is one of the most important factors in successful overwintering. Dahlias are native to the warm mountain regions of Mexico and Central America, which means they are not equipped to handle freezing temperatures. However, they actually benefit from the cooling temperatures of late autumn.
In most of the United States, dahlia tubers must be dug up and brought indoors for the winter. The signal to start this process is usually the first "killing frost." This is the frost that turns the lush green foliage of your dahlias to a dark brown or black. This frost tells the plant that the growing season is over and it is time to go dormant.
The Waiting Period
After that first hard frost, it is helpful to wait about a week or two before you start digging. This brief waiting period allows the tubers to "set" their skins. As the plant realizes the top growth is gone, it focuses its remaining energy on toughening the outer layer of the tubers. These thicker skins act as a natural defense against rot and dehydration during the winter months.
If your local weather forecast predicts a deep freeze that might penetrate the ground, you should move more quickly. While the tubers are safe underground during a light surface frost, you do not want the soil around them to freeze solid. If you live in a region where the ground stays warm, such as USDA zones 8 through 10, you may be able to leave your tubers in the soil with a thick layer of mulch, but for everyone else, lifting is the safest bet.
Labeling Your Plants
One of the easiest mistakes to make is forgetting which plant is which once the flowers are gone. Before the first frost hits, take a moment to label your dahlias while they are still in full bloom. You can use survey tape, plastic tags, or even masking tape wrapped around the base of the stem.
Write the name of the variety and the color clearly with a waterproof marker. This simple step ensures that when you go to plant your garden next spring, you aren't guessing which tubers will produce those stunning coral blooms and which ones are the tall decorative dahlias.
Key Takeaway: Wait for the first frost to blacken the foliage, then give the tubers about 10 days in the ground to toughen their skins before digging.
Preparing the Plants for Lifting
Once you have waited for the skins to toughen, it is time to prepare the plants for removal. Start by cutting the stems back. Use a clean pair of bypass pruners or a garden saw to cut the stalks down to about four to six inches above the soil level.
Leaving a short "handle" of stem is very helpful. It gives you something to hold onto while you are lifting the heavy root clumps, and it also serves as a point of reference for where the "eyes" of the tuber will eventually emerge. Be careful not to pull on these stems too hard, as they can be brittle and may snap off the main crown of the plant.
Managing Hollow Stems
Many dahlia varieties have hollow stems. After you cut them back, these stems can act like straws, funneling rainwater directly down into the center of the tuber clump. If you have a period of heavy rain between cutting and digging, this can lead to early rot.
To avoid this, some gardeners choose to dig immediately after cutting. If you must wait, you can loosely cover the cut stems with a piece of plastic or a small inverted pot if a major rainstorm is in the forecast. In most cases, if you are digging within a day or two, this is not a significant concern.
How to Dig Dahlia Tubers Safely
Digging up a dahlia clump is a bit like an archaeological excavation. The tubers grow outward from the center stem and can be quite spread out. They are also very brittle, especially when they are full of water at the end of the season.
Choosing the Right Tools
A garden fork is often the best tool for this job. Unlike a flat shovel, which can easily slice through a tuber, the tines of a fork allow you to lift the soil and the roots more gently. If you only have a shovel, make sure to give the plant plenty of extra space to avoid accidental damage.
The Lifting Technique
- Find the Perimeter: Start by inserting your garden fork into the soil about 12 inches away from the main stem. This ensures you are well outside the "splash zone" of the tubers.
- Loosen the Soil: Gently pry upward, then move a few inches around the circle and repeat. You want to loosen the soil in a full ring around the plant.
- Lift Gently: Once the soil is loose, slide the fork deeper under the center of the clump. Using the stem handle as a guide, slowly lift the entire root mass out of the ground.
- Shake Off Excess Soil: Gently shake the clump to remove large chunks of dirt. Do not bang the tubers against a hard surface, as any bruises or cracks can become entry points for fungus during storage.
What to do next:
- Cut stems to 4–6 inches.
- Use a garden fork to loosen soil 12 inches from the stem.
- Lift the clump slowly and shake off loose dirt.
- Check labels to ensure they are still securely attached to the stems.
Cleaning and Curing the Tubers
Once the tubers are out of the ground, they need to be cleaned and "cured" before they go into long-term storage. Curing is simply the process of letting the tubers air dry so that any excess moisture on the surface evaporates.
To Wash or Not to Wash?
There are two schools of thought on washing tubers. Some gardeners prefer to wash all the soil off with a garden hose. This makes it much easier to see the "eyes" and inspect the tubers for damage or pests. If you choose to wash them, do so gently with a low-pressure spray.
Other gardeners prefer to leave a bit of soil on the tubers. This soil can act as a buffer against temperature changes and help keep the tubers from drying out too quickly. If your soil is very sandy, most of it will fall off anyway. If your soil is heavy clay, you may want to wash them simply to make the clumps manageable and to prevent the clay from hardening into a brick over the winter.
The Drying Process
Find a protected spot that is out of direct sunlight and safe from frost. An unheated garage, a shed, or a covered porch works well. Lay the tubers out on a tray, a piece of cardboard, or a screen.
At Longfield Gardens, we suggest upside-down drying. For more storage help, see How to Overwinter Dahlia Tubers. Turning the clumps so the cut stems are facing downward allows any moisture trapped in the hollow stalks to drain out. This is a simple way to prevent crown rot, which is one of the most common causes of loss during winter storage.
Let the tubers dry for 24 to 48 hours. You want the surface of the tuber to feel dry to the touch and any remaining soil to feel crumbly. Do not leave them out for more than a few days, or they may begin to shrivel.
Inspecting and Trimming
Before you pack the tubers away, take a close look at each clump. This is your chance to ensure only healthy material goes into storage. One rotten tuber in a box can sometimes cause problems for the others, so a quick inspection is time well spent.
What to Look For
- Firmness: Healthy tubers should feel firm, similar to a fresh potato. If a tuber feels mushy or soft, it should be removed.
- Damage: Look for any tubers that were badly sliced by the fork during digging. If a tuber is hanging by a thin thread or is severely damaged, it is best to trim it off.
- Mother Tubers: The "mother" tuber is the original one you planted in the spring. It is often darker and more wrinkled than the new tubers that grew over the summer. Sometimes the mother tuber begins to decay at the end of the season. If it looks soft or watery, carefully snip it away from the rest of the clump.
Trimming the "Hair"
Dahlia tubers often grow many tiny, hair-like feeder roots. While these were important for the plant during the summer, they are not needed for storage. You can use a pair of clean scissors to trim these small roots off. This makes the tubers cleaner and easier to pack.
Dividing: Now or Later?
One of the most common questions gardeners ask is whether they should divide their dahlia clumps in the fall or wait until spring. Both methods work, and the choice often depends on your available space and comfort level.
Dividing in the Fall
The main benefit of dividing in the fall is that the tubers take up much less space. Instead of storing a large, basketball-sized root ball, you are storing individual tubers. The stems are also softer and easier to cut in the fall.
The challenge is that the "eyes" (the small bumps that will become next year's sprouts) can be very hard to see in the autumn. If you divide now and accidentally cut off a tuber without an eye, that tuber will never grow, even if it looks perfectly healthy.
Dividing in the Spring
Many gardeners prefer to store the entire clump and wait until spring to divide. By March or April, the eyes will begin to swell and may even start to show a tiny bit of green. This makes it incredibly easy to see exactly where to make your cuts. The downside is that you need more storage space and more packing material for the full clumps.
If you are a beginner, we often recommend waiting until spring. It takes the guesswork out of the process and ensures every piece you plant has the potential to grow.
Choosing Your Storage Medium
Dahlia tubers are living things. Even though they are dormant, they are still "breathing" and losing a tiny amount of moisture. The goal of winter storage is to create an environment that is dry enough to prevent rot, but humid enough to prevent the tubers from shriveling up into raisins.
The best way to achieve this balance is to pack the tubers in a storage medium. There are several excellent options:
- Peat Moss: This is a classic choice. It is lightweight and holds a small amount of moisture while allowing for air circulation.
- Vermiculite: This mineral product is excellent for moisture control. It is very clean and easy to work with.
- Wood Shavings: The kind sold for pet bedding (pine or cedar) works well and is very affordable.
- Coarse Sand: This is a heavier option but provides great insulation.
- Newspaper: Some gardeners find success wrapping individual tubers in several layers of dry newspaper.
Avoid using airtight plastic bags or containers without any ventilation. Without airflow, the natural respiration of the tubers can create condensation, which quickly leads to mold.
Packing Your Tubers for the Winter
Once you have chosen your medium, it is time to pack. Cardboard boxes, plastic milk crates, or plastic storage bins with holes drilled in the sides are all excellent containers.
- Bottom Layer: Start with a two-inch layer of your chosen storage medium at the bottom of the container.
- Arrange Tubers: Place your tubers or clumps on top of the medium. Make sure they are not touching each other if possible. This way, if one tuber does happen to develop a soft spot, it won't easily spread to its neighbors.
- Cover and Repeat: Pour more storage medium over the tubers until they are completely covered. If you have a deep box, you can add another layer of tubers on top.
- Final Cover: Ensure the top layer is well-covered to protect them from light and air drafts.
- Label the Outside: Clearly mark the outside of the box with the varieties inside. It’s also a good idea to include the date you packed them.
Key Takeaway: The perfect storage environment is one where the tubers are insulated from drying out but have enough air to stay fresh.
Finding the Best Storage Location
The location where you keep your boxes is just as important as how you pack them. Dahlias need a "Goldilocks" environment: not too hot, not too cold, but just right.
The Ideal Temperature Range
The sweet spot for dahlia storage is between 40°F and 50°F (4°C to 10°C).
If the temperature stays consistently above 50°F, the tubers may think it is spring and start to sprout prematurely. They may also dry out too quickly in a warm environment.
If the temperature drops below freezing (32°F), the water inside the tuber cells will freeze and expand, bursting the cell walls. A frozen dahlia tuber will turn to mush once it thaws and cannot be saved.
Common Storage Spots
- Unheated Basements: In many older homes, a cool corner of the basement stays at a very consistent temperature all winter.
- Crawl Spaces: These are often naturally cool and humid, making them ideal for tubers.
- Attached Garages: This can work well, but you must be careful. Garages can fluctuate wildly in temperature. If you use a garage, keep the boxes on an inner wall and consider elevating them off the cold concrete floor with a piece of wood or foam insulation.
- Root Cellars: The traditional choice for a reason! They provide the perfect mix of cool temperatures and high humidity.
Checking on Your Tubers
Overwintering dahlias is not a "set it and forget it" task. It is a good idea to check on your tubers about once a month. This small effort can save your entire collection if conditions change.
What to Do During a Monthly Check
Open your boxes and feel a few of the tubers.
- If they look shriveled: This means the air is too dry. You can lightly mist the storage medium with a spray bottle filled with water. You don't want it wet—just slightly damp to the touch. This will help the tubers rehydrate.
- If they look too wet or have white mold: This means there is too much moisture and not enough airflow. Remove any tubers that have become soft or mushy. Leave the box open for a day or two to let some of the moisture escape, and consider moving the box to a spot with better air circulation.
- If you see sprouts: This usually happens in late winter as the days get longer. If it's still too early to plant, try to move the tubers to a slightly cooler spot to slow them down.
Preparing for Spring Planting
As the weather begins to warm and the threat of frost passes, it is time to wake up your dahlias. This usually happens about four to six weeks before your last expected spring frost, and if you are ordering new tubers, check our Shipping Information page for timing by zone.
Waking Them Up
Take the tubers out of their storage medium and inspect them one last time. Discard anything that didn't make it through the winter. If you stored your dahlias in full clumps, this is the perfect time to divide them. Look for the small "eyes" near the stem. Using a sharp, clean knife, divide the clump so that each individual tuber has at least one eye and a small piece of the old stem attached.
Some gardeners like to "pre-sprout" their dahlias indoors. You can place the tubers in pots with slightly damp potting soil and keep them in a warm, sunny window. This gives the plants a head start, so they are already several inches tall when it is finally time to move them into the garden.
Planting Out
Wait until the soil has warmed up to about 60°F and there is no longer any danger of frost. In many regions, this is around the same time you would plant tomatoes or peppers. Dig a hole about 4 to 6 inches deep, lay the tuber horizontally with the eye facing up, and cover it with soil.
Avoid watering your dahlias heavily until you see the first green sprouts emerging from the ground. The tubers have enough stored energy and moisture to get started on their own, and too much water in cold, early-spring soil can lead to rot before the plant even has a chance to grow.
Success with Every Season
Saving dahlia tubers is one of the most satisfying cycles in gardening. It allows you to preserve the history of your garden and share your favorite flowers with friends and neighbors. While it might seem like a lot of steps at first, once you have done it once, it becomes a natural part of your autumn routine.
At Longfield Gardens, we take pride in providing high-quality tubers that are ready to perform in your garden, backed by our 100% Guarantee. By taking the time to care for them over the winter, you are ensuring that the investment you made in your landscape continues to pay dividends in the form of spectacular blooms year after year.
Final Takeaway: Storage success comes down to three things: curing them properly, keeping them between 40–50°F, and checking them monthly to manage moisture levels. Gardening is an ongoing journey, and saving your dahlias is a beautiful way to stay connected to your garden all year long.
FAQ
Do I really need to dig up my dahlia tubers?
If you live in USDA zones 7 or colder, you generally need to dig up your dahlia tubers to ensure they survive the winter. While dahlias might occasionally survive a very mild winter in zone 7 with heavy mulching and perfect drainage, lifting them is the only way to guarantee they won't freeze or rot in cold, wet soil.
What is the best material to store dahlia tubers in?
The most reliable storage mediums are slightly damp peat moss, vermiculite, or pine wood shavings. These materials provide excellent insulation while regulating moisture. The goal is to keep the tubers from drying out completely without creating a soggy environment that promotes mold and rot.
Can I store my dahlia tubers in the refrigerator?
While a refrigerator stays in the correct temperature range (above freezing and below 50°F), it is generally not recommended for dahlia storage. Most modern refrigerators are designed to remove humidity, which will quickly shrivel your tubers. Additionally, ripening fruits and vegetables in a fridge release ethylene gas, which can damage the dormant tubers.
My tubers look shriveled in mid-winter; can I save them?
Yes, shriveled tubers can often be saved if you catch them early. If they feel flexible and look wrinkled, lightly mist your storage medium with water or add a few handfuls of damp peat moss to the box. This will increase the humidity and allow the tubers to reabsorb some moisture. Check them again in a week to see if they have firmed up.
