Introduction
The sight of a dahlia in full bloom is one of the greatest joys a gardener can experience. These plants are the heavy hitters of the late-summer garden, producing armloads of flowers in every color of the sunset. At Longfield Gardens, we want every gardener to enjoy the thrill of harvesting these spectacular blooms year after year. As the season winds down and the first cool breeze of autumn arrives, many gardeners ask the same question: do you need to dig up dahlia bulbs?
Technically, dahlias grow from tubers rather than bulbs, but the goal is the same—keeping that energy-packed root alive for next year. This guide is for anyone who wants to ensure their favorite varieties return to bloom again. If you want a bigger statement in the garden, browse dinnerplate dahlias. Whether you live in a chilly northern climate or a mild southern one, understanding how to handle your tubers at the end of the season is the key to a successful spring.
The decision to dig up your dahlias depends on two main factors: your local winter weather and your soil conditions.
The Short Answer: It Depends on Your Zone
The most direct answer to whether you need to dig up dahlia bulbs is based on where you live. Dahlias are native to the warm, high-altitude regions of Mexico. Because of their heritage, they are not naturally equipped to survive a deep, freezing winter in the ground.
In the United States, we use USDA Plant Hardiness Zones to determine which plants can survive the winter in specific areas. For dahlias, the magic number is usually Zone 8. If you live in Zone 8 or warmer, your tubers can typically stay in the ground all year. In these regions, the soil rarely freezes deep enough to reach the tubers.
If you live in Zone 7 or colder, the ground will likely freeze deep enough to damage or kill the tubers. In these cooler climates, digging them up is the standard practice to ensure they survive. However, even in warmer zones, some gardeners choose to dig their tubers to prevent them from rotting in wet winter soil or to divide the clumps.
Why Soil Drainage Matters Most
While temperature is a major factor, soil moisture is often the silent winner in determining dahlia survival. Dahlias have thin skins and are prone to rotting if they sit in cold, soggy soil for months. If your garden has heavy clay soil that stays wet throughout the winter, your tubers may struggle to survive even in a warm climate.
Well-draining soil allows excess water to move away from the tubers. If you have sandy or loamy soil, your chances of successfully overwintering dahlias in the ground increase significantly. For those with wet winters, digging the tubers is often the safest bet, regardless of the temperature. It allows you to keep the tubers in a controlled, dry environment until it is time to plant again in the spring.
Key Takeaway: Temperature tells you if the tubers will freeze, but soil drainage tells you if they will rot. In cold or very wet climates, digging is the best way to protect your investment.
The Benefits of Digging Up Your Dahlias
Digging up tubers might seem like an extra chore, but many gardeners find it to be a rewarding part of the season. There are several practical advantages to lifting your dahlias every fall.
1. You Can Multiply Your Collection
A single dahlia tuber planted in the spring will grow into a large clump by autumn. When you dig that clump up, you have the opportunity to divide it into several individual tubers. Each new tuber with a visible "eye" can become a whole new plant next year. This is the most cost-effective way to expand your garden or share your favorite varieties with friends and neighbors.
2. You Can Inspect for Health
Lifting the tubers allows you to see what is happening underground. You can check for signs of pests or disease and discard any tubers that look soft or unhealthy. This prevents problems from spreading and ensures only the strongest plants return to your garden.
3. You Can Refresh Your Garden Layout
When you dig up your tubers, you aren't committed to the same garden design next year. You can store them and decide on a completely new color scheme or arrangement in the spring. It gives you total creative freedom to move your tall dinnerplate varieties to new spots.
When is the Right Time to Dig?
Timing is everything when it comes to harvesting tubers. You want to give the plant as much time as possible to store energy, but you must act before a deep freeze sets in.
The best signal for digging is the "killing frost." This is the first frost of the season that turns the green foliage of your dahlias black or dark brown. When the top of the plant dies back, it sends a signal to the tubers to go into dormancy. For step-by-step storage help, see How to Overwinter Dahlias.
What to do next:
- Watch the weather forecast for the first frost.
- Let the foliage turn black and wait 7–14 days if possible.
- Clear away any support stakes or labels while the plants are still recognizable.
- Have your digging tools and storage containers ready.
How to Dig Up Dahlia Tubers Safely
Dahlia tubers are surprisingly fragile. They have a "neck" that connects the body of the tuber to the main stem. If this neck is bent or broken, the tuber will not be able to grow next year. Following a careful process will help you lift the clumps without damage.
Cut Back the Stems
Start by cutting the stalks down to about 4 to 6 inches above the soil line. This "handle" makes it easier to see where the center of the clump is located. Use sharp, clean loppers or hand pruners. It is a good idea to wipe your tools with a disinfectant between different plants to prevent the spread of any soil-borne issues.
Use a Garden Fork
A garden fork (or pitchfork) is much safer than a shovel. Shovels have sharp edges that can easily slice through tubers hidden underground. A fork allows you to loosen the soil without as much risk.
Insert the fork into the soil about 12 inches away from the main stem. Pushing straight down and then gently prying upward will loosen the earth. Work your way around the entire plant in a circle. Once the soil is loose, you can gently lift the clump out of the ground using the fork for leverage. Avoid pulling hard on the stem handle, as this can snap the necks of the tubers.
Cleaning and Curing the Tubers
Once the tubers are out of the ground, they need a little preparation before they go into storage.
To Wash or Not to Wash?
There are two schools of thought on cleaning tubers. Some gardeners prefer to wash all the soil off with a garden hose. This makes it easier to see the eyes for dividing and ensures you aren't bringing soil-borne pests into storage. Others prefer to let the soil dry and simply brush it off.
If you choose to wash them, be very gentle. Use a low-pressure stream of water. If your soil is heavy clay, washing is usually necessary. If you have sandy soil, a simple brush-off might be enough.
The Curing Process
Curing is just a fancy word for letting the tubers dry out slightly. This toughens the skin and helps prevent rot. Place your cleaned clumps in a frost-free, shaded area with good air circulation. A garage or a covered porch works well. Let them dry for 1 to 3 days until the surface feels dry to the touch and any remaining soil is crumbly. Do not leave them in direct sunlight, as this can cause them to shrivel.
Key Takeaway: Proper drying is the bridge between the garden and successful storage. Tubers that are too wet will rot, while those left out too long will dry up.
Storing Your Tubers for the Winter
The goal of storage is to keep the tubers dormant, cool, and just moist enough to stay plump. Think of it like keeping a potato fresh. You want to avoid three things: freezing, rotting, and shriveling.
Find the Right Temperature
The ideal storage temperature is between 40°F and 50°F. If the temperature stays below 40°F for too long, the tubers might freeze. If it rises above 50°F, they may start to sprout too early or develop rot. An unheated basement, a crawl space, or a cool corner of a garage is often the perfect spot.
Choose a Storage Medium
You shouldn't just throw tubers into a plastic bin. They need a "bedding" material to help regulate moisture. Popular choices include:
- Peat Moss: Excellent for holding just the right amount of moisture.
- Vermiculite: Great for preventing rot while keeping tubers hydrated.
- Wood Shavings: A traditional choice that provides good airflow (common pet bedding works well).
- Newspaper: You can wrap individual tubers or clumps in several layers of dry newspaper.
Place a layer of your chosen material in the bottom of a cardboard box or a plastic bin with a few air holes. Arrange the tubers so they aren't touching each other, then cover them with more material. This prevents a single rotting tuber from spoiling the whole batch.
To Divide Now or Later?
One of the most debated topics among dahlia lovers is whether to divide the clumps in the fall or wait until the spring. Both methods work, and the choice depends on your schedule. For a quick refresher on tuber structure, read Dahlia Tubers: What You Need to Know.
Dividing in the Fall
If you have plenty of time and want to save storage space, you can divide your clumps immediately after cleaning. Because the tubers are hydrated, they are easier to cut. However, the "eyes" can be very small and difficult to see in the fall. If you can't find the eye, you might accidentally save a tuber that won't grow.
Dividing in the Spring
Many gardeners, including our team, often find it easier to store the clumps whole and divide them in the spring. By March or April, the eyes begin to swell and turn slightly pink or white, making them very easy to identify. While whole clumps take up more space in your storage bins, they are often more resilient over the winter.
What if You Want to Leave Them in the Ground?
If you live in Zone 8 or warmer, or if you are feeling adventurous in Zone 7, you can try overwintering your dahlias in the ground. This saves time and mimics how they grow in their native habitat. If you want compact color for beds or containers, browse border dahlias.
The Mulching Trick
To give your dahlias the best chance, you need to provide them with a "blanket." After the first frost, cut the stems down to the ground. Cover the area with a thick layer of mulch. Use 4 to 6 inches of straw, wood chips, or shredded leaves. Some gardeners even place a piece of plastic or an inverted bucket over the spot to keep winter rain from soaking the soil.
This extra layer acts as insulation, keeping the soil temperature more stable. In the spring, once the danger of frost has passed, pull the mulch back so the sun can warm the soil and encourage new sprouts to emerge.
Simple Troubleshooting for Winter Storage
Even with the best care, winter storage can be a bit of a balancing act. It is a good idea to check on your tubers once a month.
- If they look shriveled: They are too dry. Lightly mist the storage medium with a spray bottle of water. Do not soak them; just add a tiny bit of humidity.
- If they feel soft or smell bad: This is rot. Remove any affected tubers immediately and discard them. Check the remaining tubers to ensure they stay dry.
- If they are sprouting: They are too warm. Move the container to a cooler spot to slow down the growth until planting time.
Safety and Expectations
While gardening is a wonderful way to spend time outdoors, it is important to remember that many common garden plants, including dahlias, can be mildly toxic if eaten by pets or livestock. Keep your tubers out of reach of curious dogs or cats during the curing and storage process.
Remember that gardening involves working with nature, and results can vary. Weather patterns, soil types, and even the specific variety of dahlia can affect how well a tuber survives the winter. For a broader overview of planting and care, see All About Dahlias. If you lose a few tubers over the winter, don't be discouraged. It is a normal part of the learning process. Every season is a new opportunity to try a different storage method or discover a new favorite flower.
Conclusion
Deciding whether you need to dig up dahlia bulbs is a simple matter of knowing your climate and your soil. If you live in a cold or wet region, lifting and storing your tubers is a rewarding way to protect your plants and grow your collection. If you are in a warm, dry area, a thick layer of mulch might be all you need. At Longfield Gardens, we are here to support your journey from the first sprout to the final autumn harvest. Before you place an order, review our Shipping Information.
- Check your zone: Zone 7 and colder usually requires digging.
- Watch the frost: Use the first killing frost as your timer.
- Store correctly: Keep tubers cool, dry, and protected in a medium like peat moss.
- Stay curious: Check your stored tubers monthly to ensure they stay healthy.
Gardening is an ongoing conversation with nature. By taking a few simple steps this autumn, you are setting the stage for a spectacular show of color next summer.
FAQ
How do I know if my dahlia tubers are still alive in the spring?
Healthy tubers should feel firm to the touch, similar to a fresh potato. If you see a small, pimple-like bump or a tiny green sprout near the neck (the "eye"), the tuber is definitely alive. If a tuber is mushy, hollow, or shriveled like a raisin, it likely did not survive the winter.
Can I leave my dahlias in pots over the winter?
Yes, you can overwinter dahlias in their containers if you move the entire pot to a frost-free area like a garage. For a container-friendly choice, try compact border dahlias. Stop watering after the first frost and let the soil dry out completely. In the spring, you can refresh the top few inches of soil and start watering again to wake them up.
Do I have to wash the dirt off before storing them?
You do not have to wash them, but it is often helpful. Washing makes it easier to see eyes and check for damage. However, if you do wash them, you must ensure they are completely dry before putting them into storage, or they will rot.
What happens if I don't dig them up in a cold climate?
In climates where the ground freezes (Zone 7 and colder), the water inside the tuber cells will freeze and expand. This causes the cell walls to burst. When the ground thaws, the tubers will turn into a soft, black mush and will not be able to grow.
