Table of Contents
- Introduction
- Understanding the Dahlia Lifecycle and Winter Needs
- When Is the Right Time to Dig?
- A Step-by-Step Guide to Digging Tubers
- Cleaning and Preparing for Storage
- To Divide or Not to Divide?
- Choosing the Right Storage Medium
- Creating the Ideal Storage Environment
- Winter Maintenance: The Monthly Check-Up
- What to Do if You Live in a Warm Climate
- Waking Your Tubers Up in the Spring
- Common Myths About Winter Storage
- Conclusion
- FAQ
Introduction
There is a unique kind of joy that comes from watching a dahlia garden reach its peak in late summer. These plants are the true champions of the garden, producing spectacular blooms in every color and shape imaginable just as other flowers begin to fade. Because we want to enjoy these stunning displays year after year, learning how to care for the tubers during the cold months is one of the most rewarding skills a gardener can develop. If you're planning your own display, browse our dahlia collections.
At Longfield Gardens, we believe that gardening should be a relaxing and successful journey for everyone. Our 100% Quality Guarantee helps make that possible. While dahlias are native to the warm climates of Mexico and Central America, they can easily be grown as perennials in almost any climate if you give them a little winter protection. Whether you are a beginner or have been growing these beauties for years, the process of overwintering is a simple way to preserve your favorite varieties and even increase your flower count for next season.
This guide will walk you through the timing, digging, and storage techniques that keep your dahlias healthy until spring. For spring planning, browse our new dahlias. By following a few straightforward steps, you can ensure your garden remains a vibrant source of beauty for many years to come. Successfully overwintering your dahlia tubers is the key to turning a single season of color into a lifetime of gardening success.
Understanding the Dahlia Lifecycle and Winter Needs
Dahlias grow from underground storage organs known as dahlia tubers. These tubers act like a battery, storing energy and nutrients during the summer to fuel the next year’s growth. In the wild, dahlias don't have to deal with freezing temperatures. In most parts of the United States, however, the winter ground gets cold enough to freeze the water inside these tubers. Because tubers have a high water content, a hard freeze causes the cells to burst, leading to rot.
In USDA hardiness zones 8 and warmer, some gardeners find success leaving their tubers in the ground with a thick layer of mulch. However, for most of the country (zones 3 through 7), the standard practice is to "lift and store" the tubers. For a quick reference, use our Hardiness Zone Map. This simply means digging them up and keeping them in a frost-free environment until the soil warms up again in the spring.
Think of winter storage as a nap for your plants. They aren't growing, but they are still alive and breathing very slowly. Our goal is to provide an environment that is cool enough to keep them dormant but warm enough to prevent freezing. We also want to keep the moisture levels just right so they stay plump without getting wet enough to mold.
When Is the Right Time to Dig?
Timing is one of the most important factors in dahlia success. It is best to let the plants grow as long as possible in the fall. The longer the tubers stay in the ground, the more energy they can pull from the foliage to store for the following spring.
The First Killing Frost
In most regions, the signal to start the winterizing process is the first killing frost. You will know it has happened because your vibrant green plants will suddenly turn black or dark brown overnight. While this might look a bit sad, it is actually a natural and helpful part of the cycle. This frost tells the plant to stop sending energy to the flowers and start focusing entirely on the tubers below the soil.
If you live in an area where frost comes very late, you should still plan to dig your tubers by mid-November. The goal is to get them out before the ground itself freezes solid.
The Waiting Period
Many experienced gardeners wait about a week or two after the first frost before they start digging. This short wait allows the "eyes" on the tubers to become more visible. The eyes are the small bumps or buds where next year’s stems will grow. Waiting also gives the skin of the tuber a chance to toughen up or "cure," which makes them more resilient during handling and storage.
For a complete storage walkthrough, see How to Store Dahlia Bulbs in Winter.
Key Takeaway: Wait for the first frost to turn the foliage black. If possible, leave the tubers in the ground for 7 to 14 days after the frost to help the tubers mature and the growth eyes to develop.
A Step-by-Step Guide to Digging Tubers
When you are ready to begin, choose a clear, dry day if possible. Working in dry soil is much easier than working in heavy, wet mud. You will need a few basic tools: a pair of sharp loppers or garden shears, and a sturdy garden fork.
Step 1: Cutting Back the Foliage
Start by cutting the main stalks of the dahlia plants. Use your loppers to cut them down to about 4 to 6 inches above the ground. This remaining bit of stem acts as a convenient handle for lifting the clump. Be careful not to cut too low, as you want to protect the "crown" of the tuber where the eyes are located.
Step 2: Loosening the Soil
Dahlia tuber clumps can grow quite large, often spreading 12 inches or more from the center of the plant. To avoid piercing the tubers, start your digging at least a foot away from the main stem. Use a garden fork rather than a shovel. A fork is less likely to slice through a tuber and allows the soil to fall away more easily.
Gently push the fork into the soil on all four sides of the plant. Slowly pry upward to loosen the roots. The goal is to lift the entire clump at once rather than pulling individual tubers off the main stem.
Step 3: Lifting the Clump
Once the soil is loose, reach down and place one hand under the tuber clump while using the other hand to hold the stem "handle." Lift the clump out of the hole carefully. The "necks" of dahlia tubers—the thin part where they attach to the stem—are quite fragile. If a tuber breaks off at the neck, it usually won't grow a new plant because it won't have an eye. Handle the clumps like you would handle a bag of eggs.
What to Do Next:
- Label each clump immediately after lifting. Use a waterproof marker or garden tag.
- Shake off the largest clumps of soil while you are still at the garden bed.
- Move the tubers to a sheltered area, like a garage or porch, to begin the cleaning process.
Cleaning and Preparing for Storage
Once your tubers are out of the ground, they need a little bit of cleaning. There are two schools of thought on this: washing them with a hose or simply brushing off the dry dirt. Both methods work well, and your choice often depends on your soil type.
The Washing Method
If you have heavy clay soil, washing the tubers is often the best way to see what you are doing. Use a gentle spray from a garden hose to rinse away the mud. Avoid using high-pressure settings, as you don't want to tear the skin of the tubers. After washing, it is vital to let the tubers dry completely. Turn the clumps upside down so that any water trapped in the hollow stems can drain out.
The Brushing Method
If you have sandy or loose soil, you may find it easier to let the soil dry for a few hours and then gently brush it away with your hands or a soft brush. This method keeps the tubers drier and can reduce the risk of rot if your storage area is naturally humid.
Curing the Tubers
Before putting them into long-term storage, dahlias need to "cure." This means letting them sit in a cool, dry, shaded area for 1 to 3 days. This short drying period helps the skin toughen up and allows any small nicks from the digging process to callus over. Do not leave them in direct sunlight or in a spot where they might freeze. A cool garage or a basement floor is perfect.
To Divide or Not to Divide?
One of the most common questions we hear at Longfield Gardens is whether tubers should be divided in the fall or the spring. The answer is that both options work, and the best choice depends on your schedule and comfort level.
Dividing in the Fall
Many gardeners prefer to divide their dahlia clumps right after digging. The tubers are softer and easier to cut in the fall. Dividing now also saves space, as you will only be storing individual tubers rather than large, bulky clumps. The challenge is that the "eyes" can be very small and hard to see. If you choose this route, look for the tiny bumps near the top of the tuber neck. Every piece you save must have a piece of the old stem and at least one eye to grow next year.
Dividing in the Spring
If you are a beginner, waiting until spring is a great strategy. Over the winter, the eyes will often begin to swell or even sprout slightly, making it very obvious where to make your cuts. Storing the clumps whole also provides a bit of a safety net; if one tuber in the clump shrivels, the others are usually still healthy. The only downside is that you will need more storage space and a bit more effort to cut through the toughened stems in the spring.
Key Takeaway: If you are new to dahlias, store the clumps whole. This protects the tubers from drying out too fast and makes it easier to identify the growth eyes when you are ready to plant in the spring.
Choosing the Right Storage Medium
The goal of storage is to keep the tubers in a "Goldilocks" zone—not too wet and not too dry. To achieve this, we pack them in a material that regulates moisture.
Popular Storage Materials
- Peat Moss: This is a very common choice because it is slightly acidic, which can help prevent fungal growth, and it holds a small amount of moisture without being "wet."
- Pine Shavings: Often sold as animal bedding, these are inexpensive and provide excellent air circulation. They are a favorite for gardeners who store their dahlias in plastic bins.
- Vermiculite: This mineral-based material is great for maintaining a very steady moisture level.
- Newspaper or Cardboard: For those in humid climates, simply wrapping clumps in several layers of newspaper can be enough to keep them protected.
Container Options
You can store your packed tubers in cardboard boxes, plastic crates, or plastic storage bins. If you use plastic bins, do not snap the lid on tight. Leave it cracked open or drill a few small holes in the sides to allow for air exchange. If the container is airtight, the moisture released by the tubers as they breathe will have nowhere to go, which leads to rot.
Creating the Ideal Storage Environment
Once your tubers are packed, they need a home for the winter. The location you choose will be the biggest factor in whether they make it through to spring.
Temperature is King
The ideal temperature for dahlia storage is between 40°F and 50°F. If the temperature stays in this range, the tubers will remain dormant. If it drops below 35°F, you risk losing them to frost. If it rises above 55°F, the tubers may think it is spring and start to grow prematurely, or they may dry out and shrivel.
Common storage locations include:
- An unheated (but attached) garage.
- A cool corner of a basement.
- A root cellar or crawl space.
- A "bulkhead" or mudroom that stays cool.
Managing Humidity
Dahlias prefer about 80% to 90% humidity. This sounds high, but it is similar to the humidity in a typical vegetable crisper drawer. If your storage area is very dry (like a basement with a furnace), you may need to check your tubers more often and perhaps give them a very light misting of water once a month. If your storage area is damp, using breathable containers like cardboard boxes will help prevent moisture buildup.
Winter Maintenance: The Monthly Check-Up
Storing dahlia tubers is not a "set it and forget it" task. To ensure the highest success rate, plan to check on your tubers about once a month. This only takes a few minutes but can save your entire collection.
Open your boxes or bins and feel a few of the tubers. They should feel firm, much like a fresh potato.
If They Look Shrivelled
If the tubers are starting to look wrinkled or feel soft and spongy, they are losing too much moisture. To fix this, lightly mist the packing material (the peat moss or shavings) with a spray bottle of water. You don't want it to be wet, just slightly damp to the touch. This will help the tubers rehydrate.
If You See Mold or Soft Spots
If you notice a fuzzy white mold or a soft, dark spot on a tuber, don't panic. Simply use a clean, sharp knife to cut away the affected area. You can also dust the cut surface with a little bit of sulfur powder or cinnamon (a natural antifungal) to help it heal. If a tuber is completely mushy, remove it from the container immediately so the rot doesn't spread to its neighbors.
What to Do Next:
- Set a recurring reminder on your phone for the first of every month.
- Keep a small spray bottle of water near your storage area.
- Discard any tubers that feel hollow or completely soft.
What to Do if You Live in a Warm Climate
If you are gardening in USDA zones 8, 9, or 10, you have a much easier path. In these regions, the ground rarely freezes deep enough to harm dahlia tubers. You can often leave them right where they grew all summer.
However, "overwintering in the ground" still requires some care. Cut the stalks down to the ground after the first frost. Cover the entire area with a 4-to-6-inch layer of mulch, such as straw, wood chips, or shredded leaves. This mulch acts as an insulating blanket.
In very rainy climates, like the Pacific Northwest, the biggest threat is not the cold, but the wet. Dahlias in soggy soil can rot quickly. Some gardeners in these areas cover their dahlia beds with a piece of plastic or a tarp during the winter to keep the excess rain off the dormant tubers.
Waking Your Tubers Up in the Spring
As the days get longer and the threat of frost passes, it's time to bring your dahlias out of hibernation. This usually happens in late April or May, depending on your local weather.
Take the tubers out of their storage containers and examine them. You will likely see small sprouts (eyes) beginning to grow near the stem. This is the perfect time to divide any large clumps you saved. Each division needs one healthy-looking tuber and one visible eye.
You can plant them directly in the garden once the soil temperature reaches about 60°F. For exact planting depth, see How Deep Should I Plant Dahlia Bulbs?. If you want a head start on the season, you can "pot them up" indoors about 4 to 6 weeks before the last frost date. Simply place the tubers in pots with some potting soil and keep them in a sunny window or under grow lights. For more step-by-step detail, read How to Grow Dahlias from Tubers. By the time the weather is warm enough to move them outside, you will already have healthy green plants ready to take off.
Common Myths About Winter Storage
There is a lot of advice online about dahlias, and it can sometimes be confusing. Let’s clear up a few common misconceptions.
Myth: You must wash tubers with bleach. While some people use a very diluted bleach solution to kill bacteria, it isn't strictly necessary for home gardeners. As long as you remove the bulk of the soil and let the tubers dry properly, they should store just fine.
Myth: Tubers will die if they don't have a stem. The tuber itself doesn't need a long stem, but it does need the part of the "crown" (where the tuber meets the stem) where the eyes are located. A tuber with no eye will never sprout, even if it looks perfectly healthy.
Myth: You can't store dahlias in a refrigerator. You actually can! If you only have a few tubers, placing them in a bag of slightly damp peat moss in the crisper drawer of a refrigerator is a very effective way to keep them at the perfect temperature. Just make sure there are no apples in the fridge, as apples release ethylene gas that can ruin the tubers.
Conclusion
Caring for dahlia tubers in the winter is one of the most satisfying parts of the gardening cycle. It represents a bridge between the seasons—a way to carry the beauty of last summer into the promise of the next. By understanding the simple needs of these plants—cool temperatures, steady moisture, and protection from the frost—you can build a collection of flowers that grows more impressive every year. If you're expanding your collection, try the Dahlia Decorative Summer Jewels Mix - Bulk Offer.
At Longfield Gardens, we want you to feel confident in your garden. While the process of digging and storing might seem like a lot of steps at first, you will quickly find it becomes a peaceful fall ritual. If you’re planning new orders for spring, our shipping information page can help you time delivery. There is a great sense of accomplishment in pulling a box of firm, healthy tubers out of storage in the spring, knowing that they are about to transform into the stars of your summer garden.
Keep your approach simple, watch the weather, and don't be afraid to check on your plants during their winter nap. To compare another curated option, browse the Dahlia Assorted Harvest Collection. With these basics in hand, you are well on your way to a lifetime of spectacular dahlia blooms.
Final Thought: Winter storage is simply a way to help your dahlias rest so they can perform their best. Focus on keeping them cool and firm, and the plants will handle the rest when spring arrives.
FAQ
Can I leave my dahlias in the ground over winter?
In USDA hardiness zones 8 and warmer, you can often leave dahlias in the ground if you provide a thick layer of mulch to protect them from occasional light freezes. In zones 7 and colder, the ground will freeze deep enough to kill the tubers, so they must be dug up and stored indoors. For a bigger-bloom option to plan ahead, see the Dahlia Dinnerplate Flirty Fleurs Ravenna Collection.
How do I know if my dahlia tuber is still good?
A healthy tuber should feel firm and heavy for its size, similar to a fresh potato. If the tuber is mushy, smelly, or completely dried out and hollow, it is likely no longer viable and should be discarded. A little bit of surface wrinkling is okay and can usually be fixed with a light misting of water.
What happens if I don't wait for the frost to dig them up?
You can dig up dahlias before the first frost, but the tubers may not be as "mature" or as easy to store. Waiting for the frost signals the plant to go dormant and move all its energy into the tuber, which results in a hardier, healthier tuber for winter storage.
Do I need to use a fungicide before storing my tubers?
While not strictly necessary, some gardeners like to dust their tubers with sulfur powder or cinnamon to prevent mold. The most important thing for preventing rot is ensuring the tubers are dry to the touch before they are packed away and that they have some air circulation in their storage containers. If you'd like another curated option for next season, browse the Dahlia Assorted Flirty Fleurs Cordoba Collection.
We hope this guide helps you enjoy your dahlias for many years to come. If you have more questions about dahlia varieties or planting techniques, we are always here to help you create a more beautiful garden!