Table of Contents
- Introduction
- Understanding the Dahlia Lifecycle
- When to Start the Saving Process
- Preparing the Plants for Digging
- The Best Way to Dig Dahlia Tubers
- Cleaning and Curing the Tubers
- Dividing Your Tubers
- Choosing Your Storage Containers and Media
- Step-by-Step Packing Process
- The Ideal Storage Environment
- Winter Monitoring and Maintenance
- Preparing for Spring
- Summary of Success
- FAQ
Introduction
There is a unique kind of excitement that comes with the first dahlia bloom of the summer. These spectacular flowers, with their intricate petals and vibrant colors, often become the centerpiece of the garden. Whether you grow dinnerplate varieties that reach the size of a dinner plate or petite pompons, the joy they bring is unmatched. At Longfield Gardens, we want to help you keep that beauty alive year after year.
While dahlias are prolific bloomers, they are tender perennials that cannot survive freezing temperatures in most regions. Saving your dahlia tubers—often called bulbs—is a rewarding way to preserve your favorite varieties and expand your garden for next season. This guide will walk you through the simple process of digging, cleaning, and storing your dahlias so they stay healthy and ready to grow when spring returns.
Saving your tubers is a straightforward process that any gardener can master with a little bit of patience. By following a few basic steps, you can ensure your favorite flowers make it safely through the winter months.
Understanding the Dahlia Lifecycle
Dahlias are native to the warm climates of Mexico and Central America. Because of their heritage, they thrive in the sun and heat of summer but do not have a natural defense against deep frost. In USDA hardiness zones 8 and warmer, dahlias can often stay in the ground year-round with a thick layer of mulch for protection. However, for gardeners in zones 3 through 7, the tubers must be lifted and stored indoors to survive.
The dahlia plant spends the summer gathering energy from the sun and storing it in its root system. These roots develop into thick, potato-like structures known as tubers. Each tuber contains the energy and "eyes" needed to produce a whole new plant the following year. Saving these tubers is not just about survival; it is also an opportunity to grow a larger, more impressive garden each year as your collection multiplies.
When to Start the Saving Process
Timing is one of the most important factors when it comes to successfully overwintering dahlias. You want the plant to stay in the ground as long as possible to maximize the energy stored in the tubers. The best time to act is right after the first killing frost. This is a frost that is cold enough to turn the green foliage black or dark brown.
The Power of the First Frost
When the foliage dies back after a frost, it sends a signal to the plant to go dormant. While it might look a bit sad to see your beautiful plants turn black, this is actually a helpful part of the process. The sudden cold snap tells the tuber that the growing season is over and it is time to rest.
If possible, wait about a week after this first frost before you start digging. This short waiting period allows the "eyes" on the tubers to become more visible and helps the outer skin of the tuber toughen up. This thicker skin acts like a protective coat during the long winter months in storage.
Watching the Weather
If a hard freeze (temperatures staying well below 28°F for several hours) is predicted, do not wait. You want to get the tubers out of the ground before the soil itself freezes. While the tubers are insulated by the earth, a deep ground freeze can damage the watery tissues inside the tuber, leading to rot.
Key Takeaway: Wait for the first frost to turn the leaves brown, then wait 5 to 7 days before digging. This allows the tubers to fully mature and prepare for dormancy.
Preparing the Plants for Digging
Before you reach for your shovel, there are a few preparatory steps that make the job much easier. Proper preparation ensures you don't lose track of which variety is which and keeps the tubers organized.
Labeling Your Varieties
Dahlia tubers all look very similar once they are out of the ground. If you have different colors or shapes, you will want to label them before the foliage disappears completely. You can use waterproof tags or even write directly on the lower stem with a permanent marker. Some gardeners like to use colored survey tape tied to the base of the plant. Labeling ensures that when you replant in the spring, you can place your tall varieties in the back and your shorter ones in the front.
Cutting the Stems
Once you are ready to dig, cut the main stems down to about 4 to 6 inches above the soil line. These short "handles" serve two purposes. First, they provide a convenient way to lift the clump without putting too much pressure on the individual tubers. Second, they help you identify the "crown" of the plant, which is where the new growth will emerge next year.
Avoid cutting the stems too close to the ground, as you want to keep the hollow center of the stem from filling with soil or water. If you see water sitting in the hollow stem after cutting, you can gently tip the clump over after digging to let it drain out.
What to Do Next:
- Identify each plant variety while the flowers or leaves are still recognizable.
- Securely attach a waterproof label to the base of the stem.
- Cut the stems down to a 5-inch handle using sharp pruners.
- Clear away the dead foliage and compost it if it is disease-free.
The Best Way to Dig Dahlia Tubers
Digging dahlias requires a gentle touch. Unlike potatoes, which can be a bit more rugged, dahlia tubers are brittle and can snap off easily where they connect to the main stem. If a tuber snaps off without a piece of the "neck" or "eye" attached, it will not grow a new plant.
Choosing the Right Tools
A garden fork is often better than a shovel for this task. The tines of a fork can slide into the soil with less resistance and are less likely to slice through a tuber than a solid shovel blade. If you only have a shovel, make sure to give the plant plenty of space.
The Lifting Technique
Start by inserting your fork into the soil at least 12 inches away from the main stem. Dahlia root systems can grow surprisingly wide, and you want to avoid hitting the tubers with your tool. Work your way around the plant in a circle, gently prying upward to loosen the soil.
Once the soil is loose all the way around, reach down and grab the stem handle you left earlier. Lift the entire clump out of the ground. Do not be surprised if the clump is heavy; a single dahlia tuber planted in the spring can grow into a massive cluster of 10 to 15 tubers by autumn.
Cleaning and Curing the Tubers
Once the tubers are out of the ground, they need a bit of cleaning and a short "curing" period to prepare them for storage.
To Wash or Not to Wash?
There are two schools of thought on cleaning. Some gardeners prefer to wash the soil off completely with a garden hose. This makes it much easier to see the "eyes" and check for any signs of damage or rot. Other gardeners prefer to let the soil dry and then gently brush it off.
If your soil is heavy clay, washing is usually the better option. If you have sandy soil, a simple brush-off might be enough. If you choose to wash them, do it gently. Use a soft stream of water and avoid scrubbing, which can damage the delicate skin.
The Curing Process
Curing is simply the process of letting the tubers dry out slightly before they go into a box. Place your cleaned clumps in a cool, dry area that is protected from frost and direct sunlight. A garage, shed, or covered porch works well.
Let them sit for 1 to 3 days. This allows any excess moisture on the surface to evaporate. If the tubers stay too wet when they go into storage, they are likely to rot. If they dry out for too long, they will begin to shrivel. You are looking for the sweet spot where the surface feels dry and the skin looks a bit like a dusty potato.
Key Takeaway: Clean off the bulk of the soil and let the tubers air dry in a protected spot for a few days. This prevents mold and rot during the winter.
Dividing Your Tubers
One of the most exciting parts of growing dahlias is that you get "free" plants every year. A single clump can be divided into several smaller pieces, each capable of growing into a full-sized flowering plant.
Fall vs. Spring Dividing
You can divide your dahlias in the fall before storing them, or in the spring before planting.
- Fall Dividing: This takes up less storage space and the tubers are easier to cut while they are still somewhat soft. However, the "eyes" can be very hard to see in the fall.
- Spring Dividing: This is often easier for beginners because the eyes begin to swell and may even turn pink or sprout, making it obvious where to cut. The downside is that the tubers can become very tough and woody over the winter, requiring more effort to cut.
If you are a beginner, we recommend waiting until spring to divide them. Storing the whole clump provides a bit of extra protection against drying out.
Finding the Eye
To successfully divide a dahlia, each piece must have an "eye." The eye is located on the "crown," which is the knobby area where the tuber meets the main stem. It looks like a tiny bump or a small pimple. A tuber without an eye is like an egg without a yolk—it simply won't develop.
Choosing Your Storage Containers and Media
The goal of winter storage is to keep the tubers dormant, cool, and just slightly hydrated. You want to prevent two things: rot (from being too wet) and shriveling (from being too dry).
Storage Media Options
Most gardeners use a "packing medium" to surround the tubers. This helps regulate moisture levels. Popular choices include:
- Coarse Vermiculite: Excellent at holding just the right amount of moisture and very clean.
- Peat Moss: A classic choice, though it can be dusty. It should be used very slightly damp, not wet.
- Pine Shavings: Often sold as animal bedding, these provide great air circulation.
- Sawdust or Wood Chips: Effective and often inexpensive.
Container Choices
You want a container that allows for a small amount of air exchange.
- Cardboard Boxes: Good for humid basements as they breathe well.
- Plastic Bins: Good for dry environments, but keep the lids slightly cracked to prevent moisture buildup.
- Paper Bags: A simple option for small quantities.
- Plastic Bags: If using plastic, leave the top open or poke holes in the sides for ventilation.
Step-by-Step Packing Process
Packing your dahlias correctly is the final step in ensuring their safety.
- Prepare the Container: Place a 2-inch layer of your chosen storage medium (like vermiculite or peat moss) at the bottom of your box or bin.
- Arrange the Tubers: Lay the tubers or clumps on top of the medium. Try to keep them from touching each other if possible. This way, if one tuber happens to rot, the problem won't easily spread to its neighbors.
- Cover: Add more storage medium until the tubers are completely covered.
- Label Again: Place a label inside the box or write the variety name on the outside of the container.
- Final Check: Ensure the medium is only "barely damp." If you squeeze a handful, it should feel like a wrung-out sponge—no water should drip out.
The Ideal Storage Environment
Where you put your dahlia boxes matters just as much as how you pack them. Dahlias need a "Goldilocks" environment: not too hot, not too cold.
Temperature
The ideal temperature range is between 40°F and 50°F.
- If the temperature stays above 50°F, the tubers may think it is spring and start to sprout prematurely, wasting their stored energy.
- If the temperature drops below 32°F, the tubers will freeze and turn into a mushy, unusable mess.
Location Ideas
- Unheated Basements: These are often the most consistent environments. Stay away from the furnace or water heater.
- Attached Garages: These can work well, but be careful. In very cold climates, a garage can drop below freezing. You may need to place your dahlia boxes in an insulated cooler or wrap them in blankets.
- Root Cellars: The traditional and perfect spot for tuber storage.
- Crawl Spaces: Often have the right temperature and humidity, provided they stay dry.
Winter Monitoring and Maintenance
Saving dahlia bulbs is not a "set it and forget it" task. You should check on your tubers about once a month throughout the winter. This allows you to catch any minor issues before they become big problems.
Troubleshooting Rot
When you check your tubers, look for any soft or mushy spots. If you find a tuber that is rotting, remove it immediately and throw it away. If only a small part of a large clump is soft, you can sometimes cut away the bad section with a clean knife and let the cut air dry before putting the rest of the clump back in the box.
Troubleshooting Shriveling
If the tubers look wrinkled or feel light and hollow, they are losing too much moisture. To fix this, use a spray bottle to lightly mist the storage medium with water. You don't want to soak it; just add enough moisture to raise the humidity in the box.
What to Do Next:
- Set a monthly reminder on your calendar to check your dahlias.
- Gently squeeze a few tubers in each box to check for firmness.
- Adjust the moisture level by misting if they look dry.
- Ensure the storage area hasn't become too warm or too cold as the seasons change.
Preparing for Spring
As the days get longer and the ground begins to thaw, your dahlias will naturally start to wake up. This usually happens in late March or April.
When you see tiny sprouts or "eyes" beginning to grow, it is a sign that they are ready for action. This is the perfect time to divide any large clumps you saved. You can also "pre-start" your dahlias indoors in pots if you live in a region with a short growing season. This gives them a head start so they bloom earlier in the summer.
Wait until the soil in your garden has warmed up to about 60°F before planting them outside. Dahlias love warm soil, and planting them too early in cold, wet ground can cause the tubers to rot before they even get started.
Summary of Success
Saving dahlia bulbs is one of the most satisfying cycles in gardening. It turns a one-season plant into a lifetime companion. By paying attention to the timing of the frost, digging with care, and providing a cool, stable home for the winter, you can enjoy a bigger and more beautiful display every single year.
Remember that gardening is a journey of learning. If a few tubers don't make it through the winter, don't be discouraged. Even experienced gardeners lose a few now and then. Each year, you will get a better feel for the humidity in your basement or the best packing material for your climate.
Key Takeaway: Success with dahlias comes from getting the basics right: dig after the frost, dry them briefly, and keep them cool but not freezing.
We are here to support your gardening goals every step of the way. Our team at Longfield Gardens is always happy to provide the 100% Quality Guarantee and practical advice you need to make your yard a masterpiece. Whether you are adding new dahlias to your collection or saving your very first set of tubers, we wish you a wonderful and productive growing season.
FAQ
Can I leave my dahlia tubers in the ground if I live in a cold climate?
In USDA zones 7 and colder, dahlia tubers will likely freeze and rot if left in the ground over winter. While some gardeners in zone 7 have success using very heavy mulch and well-draining soil, the safest approach is to dig them up and store them indoors. This guarantees that your favorite varieties will survive to bloom again next year.
How do I know if a dahlia tuber is dead?
A healthy dahlia tuber should feel firm, similar to a fresh potato. If the tuber is mushy, slimy, or smells bad, it has rotted and should be discarded. If it is extremely shriveled, brittle, and breaks like a dry twig, it has dried out completely and is unlikely to grow. However, if it is only slightly wrinkled, it can often be revived with a light misting.
Should I wash the dirt off my dahlias before storing them?
Washing is a matter of preference. Washing makes it easier to see the "eyes" and identify any rot or insect damage before storage. If you choose to wash them, ensure they are allowed to dry completely for a day or two before being packed away. If you leave them covered in soil, the soil can provide a bit of a moisture buffer, but it can also hide pests or diseases.
What is the best material to pack dahlias in for the winter?
The most popular materials are vermiculite, peat moss, and pine shavings. Vermiculite is often favored because it is sterile and maintains a very consistent moisture level. Pine shavings provide good aeration, which can prevent mold. Whichever material you choose, the key is to ensure it is only very slightly damp—never wet.