Introduction
There is nothing quite like the feeling of watching your first dinnerplate dahlia unfurl its massive, intricate petals in mid-summer. These spectacular flowers are the crown jewels of many gardens, offering a palette of colors and shapes that last until the first frost. Because we want you to enjoy these blooms year after year, learning how to care for dinnerplate dahlia bulbs in winter is one of the most rewarding skills you can develop. At Longfield Gardens, we see every tuber as a promise of future beauty, and keeping that promise alive through the cold months is simpler than you might think.
This guide is designed for home gardeners who want to ensure their dahlia tubers survive the winter and return even stronger next spring. We will cover how to decide if you need to dig your tubers, the best ways to store them, and how to keep them healthy during their dormant period. By following a few straightforward steps, you can protect your investment and look forward to an even more impressive floral display next season.
Knowing When to Take Action
The first step in winter care is understanding the needs of your specific plants. While we often call them "bulbs" for simplicity, dahlias actually grow from tubers, which are thickened underground stems similar to potatoes. These tubers are full of energy and moisture, but they are not cold-hardy in most parts of the United States. They are native to the warm mountain regions of Mexico and Central America, so they prefer a mild, dry winter over a freezing, wet one.
Whether you need to dig your dahlias or can leave them in the ground depends mostly on your local climate. In USDA hardiness zones 8 through 11, the ground rarely freezes deep enough to harm the tubers. In these warmer areas, you can often leave them in the soil with a bit of extra protection. However, if you live in zones 7 or colder, the winter freeze will likely reach the tubers and cause them to turn to mush. In these regions, digging and storing them indoors is the best way to ensure they survive.
Even in warmer zones, some gardeners choose to dig their tubers every year or two. This is because dahlia clumps grow larger over time. Digging them up allows you to divide the clumps, which prevents overcrowding and gives you more plants to share with friends or move to new spots in your yard. It also protects the tubers from rotting if your winter soil stays very wet.
The Signal to Start: The Killing Frost
Timing is everything when it comes to dahlia care. You want to give the tubers as much time as possible to store energy from their leaves, but you must get them out of the ground before the soil freezes solid. The best signal to start the process is the first killing frost. This is a frost that is cold enough to turn the green foliage of your dahlias brown or black.
Once the foliage has blackened, the plant has officially entered its dormant state. We recommend waiting about 5 to 14 days after this frost before you start digging. This brief waiting period allows the tubers to "cure" slightly in the ground, which helps toughen their skins for storage. If a hard freeze is predicted that might freeze the ground several inches deep, do not wait—go ahead and dig them up immediately.
If you live in a region where frost comes very late, you can simply wait until mid-November to start the process. The shorter days and cooler soil temperatures will naturally signal the plant to slow down. Getting the timing right ensures the tubers have maximized their starch reserves, which fuels their growth when you replant them in the spring.
Quick Steps for Timing
- Monitor local weather for the first killing frost.
- Wait for the foliage to turn brown or black.
- Allow the tubers to sit in the ground for about a week if the weather remains above freezing.
- Aim to have all tubers safely out of the ground by mid-November in most regions.
Key Takeaway: The first frost is your friend—it tells the dahlia to stop growing and start resting. Wait for the leaves to turn dark before you begin the digging process.
How to Dig Your Dahlia Tubers Safely
Digging up dahlias is a gentle process. Because the tubers are joined at a central point called the "neck," you must be careful not to snap them. The neck is where the "eyes" (the buds for next year's growth) are located. If a tuber breaks off without a piece of the neck and an eye, it will not grow into a new plant.
Start by cutting the stalks down to about 4 to 6 inches above the soil line. This gives you a "handle" to work with and helps you see exactly where the center of the clump is located. We recommend using a garden fork rather than a shovel. A fork is less likely to slice through the tubers and allows the soil to fall away more easily.
Insert your fork into the soil about 12 inches away from the base of the stalk. Gently pry upward, working your way around the entire plant. You want to lift the whole clump of soil and tubers together. Once the soil is loose, lift the clump by the base of the stalks and gently shake off the excess dirt.
Tools for Success
- Pruning shears or loppers for cutting the thick stalks.
- A sturdy garden fork (pitchfork) for lifting.
- Garden gloves to protect your hands.
- Tags and a waterproof marker for labeling.
Cleaning and Curing for Storage
Once the tubers are out of the ground, they need a little bit of preparation before they go into their winter home. Some gardeners prefer to wash their tubers with a gentle stream of water from a garden hose to remove all soil. This makes it easier to see the "eyes" and check for any signs of damage or rot. Others prefer to let the soil dry and then brush it off. Either method works well, but washing is often cleaner for indoor storage.
After cleaning, the tubers need to "cure." This just means letting them air dry in a protected area for 12 to 24 hours. A garage, shed, or basement is a great spot. Avoid leaving them in direct sunlight or on a cold concrete floor, as this can cause them to dry out too fast or stay too damp. Curing helps the skin toughen up, which acts as a natural barrier against rot and dehydration during the winter.
While the tubers are curing, it is the perfect time to label them. It is very easy to forget which tuber belongs to which variety once the flowers are gone. We like to use a soft pencil or a waterproof marker to write the variety name directly on the skin of a large tuber. Alternatively, you can tie a plastic tag around the stem of the clump.
Choosing Your Storage Medium
Dahlias need a storage environment that is "just right"—not too wet and not too dry. If the environment is too humid, they will rot. If it is too dry, they will shrivel up and lose their vitality. To solve this, we store the tubers in a "medium" that helps regulate moisture.
There are several great options for storage media:
- Peat Moss: This is our preferred choice at Longfield Gardens. It is excellent at holding a tiny bit of moisture while still allowing the tubers to breathe.
- Vermiculite: This mineral is very clean and does a great job of preventing rot.
- Wood Shavings: Pine shavings (like the kind used for pet bedding) are affordable and provide good insulation.
- Newspaper: Wrapping individual tubers in several layers of newspaper is an old-fashioned method that still works well for many gardeners.
Avoid using plastic bags that seal completely. Without air circulation, moisture from the tubers will get trapped, which almost always leads to mold and rot. Instead, use cardboard boxes, plastic crates with holes, or paper bags. If you use a plastic bin, leave the lid slightly ajar or drill several holes in the sides to allow for airflow.
Key Takeaway: The goal of storage is to keep the tubers dormant and plump. Using a medium like peat moss provides a buffer that protects them from extreme shifts in humidity.
Creating the Ideal Winter Environment
The location where you store your dahlias is just as important as how you pack them. Dahlias prefer a cool, dark, and slightly humid environment. The ideal temperature range is between 40°F and 50°F. If the temperature stays in this range, the tubers will remain dormant and healthy.
A basement that stays cool but does not freeze is usually the best spot. A crawl space or an attached garage that stays above 40°F can also work. If the storage area gets too warm (above 60°F), the tubers may think it is springtime and start to sprout early. If they freeze, the water inside the cells will expand and destroy the tuber, leaving you with a soft, mushy mess when it thaws.
Light is another factor to consider. Tubers should be kept in total darkness. Exposure to light can trigger growth or cause the tubers to turn green and tough. If your storage area has windows, make sure your boxes are opaque or covered with a dark cloth.
The Importance of Monthly Check-ins
One of the most common mistakes gardeners make is "set it and forget it." Even the best storage setup needs a quick check-over once a month. This small effort can be the difference between losing a variety and having a successful spring planting.
During your monthly check-in, look for two things:
- Signs of Rot: If you see any soft, mushy spots or fuzzy mold, use a clean knife to cut that section away immediately. Discard any tubers that are completely rotten so they don't spread the issue to their neighbors.
- Signs of Shriveling: If the tubers look very wrinkled or feel light and hollow, they are getting too dry. Use a spray bottle to lightly mist the storage medium with water. You don't want it to be wet—just "barely damp" like a wrung-out sponge.
If you find that your tubers are starting to sprout in February or March, it usually means your storage area is a bit too warm. Move them to a slightly cooler spot if possible. You can leave the sprouts alone; they are usually quite hardy and will continue to grow once planted.
Troubleshooting Common Winter Issues
Even with careful care, you might run into a few challenges. The most frequent issue is rot, which is usually caused by the tubers being too wet when they were packed or the storage area being too humid. "Drainage" is a term we often use for soil, but it applies to storage too—water must be able to escape the container. If you find rot consistently, try using a more breathable container next year, like a wooden crate.
Shriveling is the opposite problem and is very common in homes with forced-air heating, which can make the air very dry. If your tubers look like raisins, they are losing too much moisture. Increasing the amount of storage medium (like adding more peat moss) can help create a thicker "blanket" of protection around them.
Another issue is pests. Mice and other small rodents sometimes find dahlia tubers to be a tasty winter snack. If you have a known pest problem in your storage area, consider using mesh-covered crates or keeping your boxes on high shelves.
What to Do Next
- Set a recurring reminder on your phone for the first of every month.
- Keep a spray bottle of water near your storage area for quick adjustments.
- Have a clean pair of snips ready to trim away any problematic spots.
Overwintering in the Ground (Zones 8-11)
If you are lucky enough to live in a mild climate, your care routine is much simpler. In these areas, dahlias can stay in the ground, but they still benefit from a little winter "sweater." Once the foliage dies back, cut the stems down to the ground level.
Apply a thick layer of mulch—about 4 to 6 inches—over the top of the dahlia bed. You can use straw, shredded leaves, or bark mulch. This layer acts as insulation, keeping the soil temperature stable even if there is a brief cold snap. It also helps prevent the soil from drying out too much.
In very rainy climates, like the Pacific Northwest, the biggest threat is rot from soggy soil. Some gardeners in these areas place a piece of plastic or an inverted pot over the crown of the plant to deflect excess rainwater. This keeps the center of the clump relatively dry while the surrounding soil stays moist.
Preparing for the Spring Return
As winter begins to fade and the ground starts to warm, your dahlias will naturally begin to wake up. Around late March or April, you can pull your boxes out of storage and take a final look at your tubers. This is a great time to divide large clumps if you didn't do it in the fall. In the spring, the "eyes" are much easier to see as they begin to swell and turn pink or purple.
Wait to plant your dahlias until all danger of frost has passed and the soil has warmed to about 60°F. If you plant them in cold, wet soil too early, they may rot before they have a chance to grow. A little patience in the spring goes a long way toward a healthy, vigorous plant.
At Longfield Gardens, we always say that a little bit of preparation in the fall leads to a spectacular show in the summer. Caring for your tubers over the winter is a wonderful way to connect with the cycle of the seasons and ensure your garden stays vibrant year after year.
Summary of Winter Dahlia Care
Caring for dahlia bulbs in winter is a simple process of managing moisture and temperature. By digging them at the right time, cleaning them gently, and storing them in a cool, dark place, you set yourself up for gardening success. Remember to check on them occasionally and adjust the moisture levels as needed.
Action Checklist
- Identify your hardiness zone to decide if you need to dig.
- Wait for a killing frost before cutting back the stalks.
- Use a garden fork to lift clumps gently, avoiding damage to the necks.
- Cure the tubers for 24 hours before packing them in peat moss or shavings.
- Store in a cool (40-50°F), dark location.
- Check monthly for rot or dehydration.
"Winter care is the quiet season of gardening, where a few simple steps preserve the vibrant colors of last summer for the joy of the next."
We hope this guide makes you feel confident and excited about keeping your dahlias healthy through the winter. Gardening is a journey of learning and observation, and every year you store your tubers, you will get better at reading what they need. If you are looking to add more varieties to your collection, feel free to explore our selection of premium dahlia tubers. We are here to help you grow a garden you love.
FAQ
Should I wash the dirt off dahlia tubers before storing them?
Yes, washing dahlia tubers is generally recommended because it allows you to see the "eyes" and check for any damage or rot. Removing the soil also helps prevent soil-borne diseases from lingering in your storage container. Just make sure the tubers are completely dry on the outside before you pack them away for the winter.
Can I store dahlia tubers in a refrigerator?
You can store dahlia tubers in a refrigerator if you have a spare one that isn't used for food, as some fruits and vegetables release gases that can harm the tubers. However, most refrigerators are kept around 35-38°F, which is a bit colder than the ideal 40-50°F range. If you use a fridge, make sure the tubers don't freeze and aren't kept in an airtight plastic bag.
What should I do if my stored dahlia tubers are shriveling?
If your tubers look wrinkled or shriveled, they are losing too much moisture. This is easily fixed by lightly misting the storage medium (such as peat moss or wood shavings) with a spray bottle of water. You want the medium to feel slightly damp, like a sponge that has been thoroughly wrung out, rather than wet or soggy.
Is it better to divide dahlia clumps in the fall or the spring?
Both times work, but spring is often easier for beginners. In the spring, the "eyes" (buds) swell and become much more visible, making it clear where you should cut to ensure each division will grow. If you divide in the fall, the eyes are often dormant and very difficult to spot, which increases the risk of cutting a tuber that won't be able to sprout.
