Table of Contents
- Introduction
- Recognizing the Right Time to Dig
- Preparing the Plants for Lifting
- How to Lift Dahlia Tubers Safely
- Cleaning and Drying Your Tubers
- To Divide Now or Later?
- Selecting the Right Storage Containers
- Choosing a Packing Medium
- The Ideal Storage Environment
- Monitoring Your Tubers During Winter
- Realistic Expectations for Overwintering
- Conclusion
- FAQ
Introduction
There is nothing quite like the late-summer glory of a dahlia garden. These beauties are the stars of the show, offering a spectacular range of colors and shapes that last until the very first frost. While many gardeners treat them as annuals, one of the most rewarding parts of growing these beauties is saving the tubers to plant again next year.
Storing your tubers allows you to build a personal collection of your favorite varieties year after year. At Longfield Gardens, we want to help you make this process as easy and successful as possible. With a few simple steps, you can ensure your tubers stay healthy and dormant through the cold months.
This guide will walk you through the timing, lifting, and storage techniques needed to preserve your dahlias. Whether you are a first-time grower or looking to refine your method, these practical tips will help you achieve great results. Success comes down to understanding what the tubers need to stay plump and rot-free until spring.
Recognizing the Right Time to Dig
Timing is the most important factor when it comes to storing dahlia tubers. In most parts of the United States, dahlias cannot survive the freezing temperatures of winter in the ground. They need to be lifted and moved to a protected location.
The best signal to start this process is the first killing frost. This is when the overnight temperatures drop low enough to turn the dahlia’s lush green foliage black or brown. While it might look a bit sad to see your plants wilt, this is actually a helpful turning point for the tubers.
When the top of the plant dies back, the energy shifts entirely into the tubers below the surface. This helps them "cure" and prepares them for a long period of dormancy. Most gardeners find that waiting for this frost makes the tubers tougher and more resilient during winter storage.
If you live in an area where frost comes very late or not at all, you can still follow a seasonal schedule. Aim to lift your tubers by mid-November. By this time, the plants have usually finished their primary growing cycle and are ready for a rest.
The Benefits of a Brief Wait
Many experienced gardeners choose to leave their tubers in the ground for about a week after the foliage has blackened. This short waiting period allows the "eyes" or growth points on the tubers to become more visible. It also helps the outer skin of the tuber toughen up.
If the weather forecast predicts a hard, deep freeze that might penetrate the soil, you should dig them up sooner. However, for a light frost, a few days of patience can make the next steps much easier.
What to do next:
- Keep a close eye on your local weather forecast for the first frost.
- Ensure you have your storage supplies, such as boxes and packing material, ready.
- Check that your plant labels are still readable before the foliage disappears.
Preparing the Plants for Lifting
Once the foliage has turned brown and you are ready to dig, the first step is to clear away the top growth. Use a pair of sharp loppers or garden shears to cut the main stalks. You should leave about 4 to 6 inches of the stem sticking out of the ground.
This remaining stem serves as a "handle" for the tuber clump. It also helps you keep track of where the center of the plant is located. Be careful not to cut the stalks right down to the soil line, as you want to avoid getting dirt or water directly into the hollow centers of the stems.
If you have many different varieties, this is the best time to double-check your labels. It is very easy to mix up tubers once they are out of the ground. You can use a waterproof marker to write the variety name directly on the stem or tie a weather-resistant tag to the "handle" you just created.
Cleaning Your Tools
Before moving from one plant to the next, it is a good practice to wipe down your cutting tools. A simple solution of one part bleach to ten parts water works well. This prevents the spread of any soil-borne issues from one clump to another. It is a small step that ensures the long-term health of your entire collection.
How to Lift Dahlia Tubers Safely
Lifting the tubers requires a gentle touch. Dahlia tubers grow in clumps and are attached to a central "neck." These necks are quite fragile and can snap if they are pulled or pried too hard. If the neck breaks, the tuber may not be able to sprout in the spring.
Start by using a garden fork or a sturdy shovel. Position your tool about 12 inches away from the main stem. This distance helps ensure you do not accidentally slice through the tubers that have expanded outward during the summer.
- Loosen the Soil: Gently push the fork into the ground on all four sides of the clump.
- Lift Upward: Once the soil is loose, use the fork to pry the entire clump upward.
- Support the Clump: Use one hand to steady the stem handle while the other hand uses the fork to lift from underneath.
- Avoid Pulling: Never yank the clump out by the stem. The weight of the wet soil can cause the tubers to break off.
Once the clump is out of the ground, shake it gently to remove the heaviest pieces of soil. If your soil is very sandy, most of it will fall away easily. If you have heavy clay soil, you may need to use your fingers to carefully poke away the larger clods.
Key Takeaway: Always dig wider than you think the clump is to avoid damaging the tubers. Supporting the clump from underneath is the best way to keep the fragile necks intact.
Cleaning and Drying Your Tubers
After lifting, the tubers need to be cleaned and dried before they go into storage. There are two common schools of thought on cleaning: washing with water or dry-brushing. Both can be successful, and the choice often depends on your soil type.
The Washing Method
If you have thick, sticky soil, washing the tubers with a garden hose is often the best approach. Use a gentle spray to rinse away the dirt. This allows you to see the tubers clearly, making it easier to spot any damage or signs of rot. After washing, it is critical to let the tubers dry completely. Turn the clumps upside down so any water trapped in the hollow stems can drain out.
The Dry-Brushing Method
If your soil is loose and friable, you can let the clumps sit in a dry, protected area for a few hours. Once the soil has dried, you can gently brush it away with a soft brush or your gloved hands. This method keeps the tubers drier from the start, which can be an advantage in humid climates.
The Curing Process
Regardless of how you clean them, tubers need a short "curing" period. Place them in a cool, shaded area with good air circulation for 1 to 2 days. A garage, shed, or covered porch works well. Avoid placing them in direct sunlight, as this can cause the tubers to shrivel. The goal is for the outer skin to feel dry to the touch, but the tuber itself should still feel firm like a potato.
To Divide Now or Later?
One of the most common questions gardeners ask is whether they should divide the tuber clumps in the fall or wait until spring. Both options have benefits, and the right choice depends on your schedule and storage space.
Dividing in the Fall
Many people prefer to divide their dahlias right after digging. The tubers are softer and easier to cut in the autumn. Dividing now also takes up much less storage space, as you are storing individual tubers rather than bulky clumps.
If you choose to divide in the fall, remember that each tuber must have a "piece of the crown" and an eye to grow. The eye is a small bump located where the tuber meets the central stem. If you cannot see the eyes clearly, it may be better to wait until spring when they begin to swell.
Dividing in the Spring
Leaving the clumps whole is the safest bet for beginners. Whole clumps tend to resist drying out better than individual tubers. In the spring, the eyes will be much more obvious, making it easy to see exactly where to make your cuts. The only downside is that whole clumps require larger storage containers.
What to do next:
- If you are new to dahlias, keep the clumps whole for your first year.
- Label each clump or individual tuber clearly using a permanent marker.
- Inspect the tubers and trim off any long, thin "tail" roots, as these often rot in storage.
Selecting the Right Storage Containers
The environment you create inside your storage container is what determines your success. You are looking for a balance: the tubers need to stay hydrated enough so they don't shrivel, but dry enough so they don't rot.
Several different types of containers can work well:
- Cardboard Boxes: These are breathable and inexpensive. They work well if your storage area has moderate humidity.
- Plastic Bins: If you use plastic, leave the lid slightly ajar or drill small holes in the sides to allow for air exchange. This prevents moisture from building up and causing mold.
- Paper Bags: These are excellent for individual tubers or small clumps. They offer some protection while allowing the tubers to breathe.
- Milk Crates: These provide maximum airflow and are great for large clumps, though they require a liner if you are using loose packing material.
Choosing a Packing Medium
Rarely should dahlia tubers be stored "naked" in a box. Using a packing medium helps regulate the moisture levels around the tubers. It acts like a buffer, absorbing excess dampness or providing a little humidity when the air is too dry.
Commonly used materials include:
- Vermiculite: This is many gardeners' top choice. It is lightweight, sterile, and excellent at managing moisture.
- Peat Moss: This is a classic option. It should be used slightly damp—just enough so that it feels cool, but not so wet that you can squeeze water out of it.
- Pine Shavings: Often sold as animal bedding, these are affordable and provide good aeration.
- Wood Chips or Sawdust: These work similarly to pine shavings and are easy to find at garden centers.
When packing, place a layer of your chosen medium at the bottom of the container. Arrange the tubers so they are not touching each other, then cover them with more material. Layering them this way ensures that if one tuber happens to rot, the issue won't easily spread to the others.
The Ideal Storage Environment
Once your dahlias are packed, you need to find the right "home" for them for the winter. The perfect spot is cool, dark, and slightly damp.
The ideal temperature range is between 40°F and 50°F. If the temperature stays in this range, the tubers will remain dormant. If it drops below freezing (32°F), the tubers will turn to mush. If it rises above 50°F for an extended period, the tubers may try to start growing too early or may shrivel from the warmth.
Common storage locations include:
- Unheated Basements: These often provide the most consistent temperatures.
- Attached Garages: These can work well, but you must ensure the box stays off the cold concrete floor. Placing the box on a shelf or a piece of Styrofoam is a good idea.
- Root Cellars or Crawl Spaces: These are traditional favorites because they naturally stay cool and humid.
Avoid storing your tubers in a closet inside your living space, as modern homes are usually too warm and dry for successful dahlia storage.
Key Takeaway: Consistency is key. A spot that stays at a steady 45°F is much better than a spot that fluctuates wildly between 30°F and 60°F.
Monitoring Your Tubers During Winter
Storing dahlia tubers is not a "set it and forget it" task. We recommend checking on your collection once a month during the winter. This allows you to catch any small problems before they become big ones.
Checking for Rot
During your monthly check, look for any tubers that feel soft, squishy, or smell bad. If you find one, remove it immediately and throw it away. Rot can spread quickly through a box, so removing the "bad apple" saves the rest of your collection.
Checking for Shriveling
If the tubers feel very light or look wrinkled like a raisin, they are losing too much moisture. You can fix this by lightly misting the packing medium with a spray bottle of water. You don't want the material to be wet, just slightly damp to the touch. This small boost in humidity will help the tubers plump back up.
Managing Mold
If you see a little bit of white surface mold, it usually means the airflow is too low or the container is too airtight. Wipe the mold off with a dry cloth and leave the container open for a day to let some moisture escape.
Realistic Expectations for Overwintering
It is important to remember that gardening involves living things, and winter storage is no exception. Even professional growers expect to lose a small percentage of tubers over the winter. Some varieties are naturally "better keepers" than others.
At our farm, we have found that some dahlias have very thin skins and are prone to drying out, while others have thick, sturdy tubers that seem to last through anything. If you lose a few tubers, don't be discouraged. It is a natural part of the process. By following these steps, you are giving your plants the best possible chance to return with vigor in the spring.
Our goal at Longfield Gardens is to help you enjoy the beauty of dahlias year after year. While it takes a little effort to lift and store them, the reward of seeing those familiar flowers bloom again is well worth the time.
What to do next:
- Set a recurring reminder on your phone to check your tubers on the first of every month.
- If you notice a particular variety isn't storing well, make a note to try a different packing medium for that type next year.
- Keep your storage area dark to prevent the tubers from waking up too early.
Conclusion
Storing dahlia tubers for the winter is a practical and satisfying way to expand your garden. By waiting for the first frost, lifting the clumps with care, and providing a cool, stable environment, you can enjoy your favorite blooms for many seasons to come. Remember that dahlia storage is a skill that gets easier every year as you learn what works best in your specific climate and home.
- Timing is everything: Wait for a frost to signal the plant to go dormant.
- Handle with care: Protect the fragile necks and crowns during the digging process.
- Stay organized: Label your varieties clearly before they go into storage.
- Monitor regularly: A quick monthly check can prevent rot from spreading.
We invite you to explore our planning guides for more tips on making your garden thrive. With a little bit of winter preparation, your garden will be ready to burst into color again as soon as the warm weather returns.
FAQ
Can I leave my dahlia tubers in the ground if I use a lot of mulch?
In USDA zones 8 and warmer, you may be able to overwinter dahlias in the ground with a thick layer of mulch to protect against light freezes. However, in zones 7 and colder, the ground usually freezes deep enough to kill the tubers regardless of mulch. For most of the United States, lifting and storing them is the only way to ensure they survive.
What should I do if my tubers start sprouting in February?
If you see small green sprouts early in the year, it usually means your storage area is a bit too warm. Move the container to a cooler spot if possible. You don't need to cut the sprouts off; simply keep the tubers dormant as long as you can. If they have long, spindly growth by April, you can gently trim it back before planting.
Why did my tubers turn into mush even though it didn't freeze?
Mushy tubers are usually a sign of rot caused by too much moisture or poor air circulation. This can happen if the tubers were put away while still wet or if they were stored in a plastic bag without any ventilation. Next time, ensure the tubers are dry to the touch before packing and use a breathable medium like vermiculite.
Do I need to treat my tubers with a fungicide before storing?
While not strictly necessary, some gardeners like to dust the cut ends of tubers with sulfur powder or cinnamon to help prevent fungus. If you have had issues with rot in the past, this extra step can be helpful. However, the most important factors for preventing rot are proper drying and maintaining the correct temperature and humidity levels.