Introduction
There is nothing quite like the late-summer magic of a pompon dahlia in full bloom. These spectacular flowers offer an incredible range of colors and shapes, from delicate pompons to massive dinnerplate varieties. Because dahlias are native to the warm climates of Mexico and Central America, they treat our northern winters as a time for rest. In most parts of the United States, keeping these plants healthy for next year requires a little bit of indoor care during the cold months.
At Longfield Gardens, we want every gardener to feel the pride of seeing their favorite dahlias return season after season. Saving your tubers is one of the most rewarding parts of the gardening cycle. It allows you to grow your collection without starting from scratch every spring. Browse our Dahlia Collections to see more options.
This guide will walk you through the essential steps of lifting, cleaning, and storing your tubers. We will help you understand the best timing for your region and how to keep your plants safe until the ground warms up again. Learning how to winter dahlia bulbs is a straightforward skill that turns a one-season wonder into a lifelong garden staple. For a step-by-step refresher, see our How to Lift and Store Dahlia Bulbs.
Why Dahlias Need a Winter Rest
Dahlias are tender perennials, which means they can live for many years but cannot survive a hard freeze. In their native habitat, the soil stays warm year-round. In the United States, gardeners in USDA hardiness zones 8 and warmer can often leave their dahlias in the ground. If you're not sure which zone you garden in, check our Hardiness Zone Map. However, for those of us in zones 7 and colder, the freezing temperatures will turn the moisture inside the tubers into ice, causing them to mush and die.
Even in warmer zones, winter rain can be a challenge. If the soil stays cold and soggy for months, the tubers are likely to rot before spring arrives. By lifting the tubers and bringing them indoors, you take control of their environment. You provide the perfect balance of temperature and moisture that they need to stay dormant but healthy.
Think of winter storage as a long nap for your plants. During the summer, the dahlia foliage collects energy from the sun and stores it in the tubers, which are the thick, potato-like structures at the base of the stem. Our goal during the winter is to preserve that stored energy. When you follow the right steps, you ensure that the tuber remains firm and ready to sprout as soon as it feels the warmth of spring.
Timing Your Harvest
The most common question gardeners ask is exactly when to take their dahlias out of the ground. While it is tempting to dig them up as soon as the weather turns chilly, patience is rewarded with stronger tubers. The plants use the cooling temperatures of autumn to finish sending energy down into their root systems. For a broader overview of growing these plants, read All About Dahlias.
Waiting for the First Frost
In most regions, the signal to begin is the first "killing frost." This is the frost that turns the lush green dahlia foliage black or dark brown. Once the leaves have been hit by frost, the plant stops growing and enters a dormant state. This dormancy is essential because it tells the tuber to stop producing new stems and start resting.
If you live in an area where a hard frost is late to arrive, you can still lift your tubers in late October or early November. The shorter days and cooler soil are usually enough to trigger dormancy. However, if you can wait for that first frost, your tubers will be better "cured" and more resilient during storage.
The Two-Week Rule
Many experienced gardeners follow the "two-week rule." After the frost kills the foliage, cut the stems down to about 4 to 6 inches above the ground. Leave the tubers in the soil for about 7 to 14 days before digging them up. This short waiting period allows the "skin" of the tuber to toughen up slightly, which helps prevent it from drying out too quickly once it is out of the ground.
Key Takeaway: Wait for the first frost to turn the leaves brown before you begin the lifting process. This ensures the plant has stored maximum energy for the winter.
Lifting and Cleaning the Tubers
Lifting dahlias is a physical task, but it does not have to be difficult. The goal is to remove the entire clump of tubers without snapping the "necks"—the narrow part where the tuber connects to the main stem. These necks are fragile, and if they break, the tuber may not be able to sprout next year.
How to Dig Safely
- Clear the Area: Use loppers or a sharp garden saw to cut the remaining stems down to about 2 or 3 inches. This gives you a handle to hold while you work.
- Give Them Space: Start digging about 12 inches away from the center of the plant. Use a garden fork or a sturdy shovel. Digging too close to the stem can slice right through your tubers.
- Lift Gently: Slowly work your way around the plant, loosening the soil on all sides. Gently pry upward until the entire clump heaves out of the ground.
- Remove Excess Soil: Shake the clump gently to remove large chunks of dirt. If your soil is heavy clay, you may need to use your hands to carefully pull away the mud.
The Washing Process
Once the tubers are out of the ground, they need to be cleaned. While some gardeners prefer to leave a little dirt on them, washing them thoroughly is generally safer for beginners. Clean tubers are easier to inspect for signs of rot or insect damage.
Use a garden hose with a gentle spray setting to wash away the remaining soil. Be sure to spray into the center of the clump where the stems meet the tubers. This area often traps moisture and dirt, which can lead to mold during storage. After washing, turn the clumps upside down so any water trapped in the hollow stems can drain out. For more on dahlia tubers, see Dahlia Tubers: What You Need to Know.
What to Do Next
- Label each clump immediately with a waterproof marker or garden tag.
- Inspect for "mother" tubers that look shriveled or rotten and remove them.
- Find a shaded, frost-free spot for the tubers to dry for 24 hours before moving to long-term storage.
The Importance of Curing
Curing is a fancy word for letting the tubers dry out slightly before they are packed away. This is a critical step in learning how to winter dahlia bulbs. If you pack them while they are soaking wet, they will rot. If you leave them out for too long in the open air, they will shrivel up like raisins. If you like rounded blooms, browse our Ball Dahlias.
Find a cool, dry place like a garage or a basement to let your tubers sit for a few days. The ideal temperature for curing is between 50°F and 60°F. Avoid placing them in direct sunlight or in a spot with heavy wind, as this will dry them out too fast.
After two or three days, the exterior of the tuber should feel dry to the touch, like the skin of a potato. The remaining soil should be easy to brush off. At this stage, you can trim away the very long, hair-like feeder roots. These roots are not necessary for next year's growth and can often hold onto excess moisture that leads to mold.
To Divide or Not to Divide
A single dahlia tuber planted in the spring can grow into a large clump by autumn. You have two choices: you can store the entire clump as it is, or you can divide it into individual tubers before storing them.
Storing Whole Clumps
Storing the entire clump is the easiest method for beginners. It takes less time in the fall, and the larger mass of the clump helps protect the individual tubers from drying out. The downside is that whole clumps take up much more space. If you have a large collection, you might find your storage area filling up quickly. We often recommend this method if you are new to dahlias, as it is very forgiving.
Dividing in the Fall
Dividing your dahlias now allows you to fit more plants into a smaller storage box. It also gives you more "starts" for next year. However, identifying the "eyes" (the small bumps where next year’s growth begins) can be difficult in the fall. If you cannot see the eyes, it is better to wait until spring when they begin to swell and turn pink.
If you choose to divide now, use a clean, sharp knife. Every individual tuber must have three things to be viable: a body (the fat part), a neck (the thin part), and a piece of the "crown" (the area where the tuber meets the stem) that contains at least one eye. Without an eye, the tuber will never produce a plant, even if the body looks healthy.
Key Takeaway: If you are a beginner, store your dahlia clumps whole. It is easier to identify the growth points (eyes) in the spring when they begin to sprout.
If you prefer daisy-like blooms, browse our Single Dahlias.
Choosing Your Storage Medium
The secret to successful dahlia storage is creating a "micro-climate." You want to keep the tubers in an environment that stays at a consistent moisture level. If the air is too dry, the tubers will lose their internal moisture and die. If the air is too damp, fungi and bacteria will take over.
Popular Packing Materials
There are several materials you can use to surround your tubers. These materials act as a buffer against changes in humidity:
- Peat Moss: This is a very common choice. It holds moisture well but is naturally acidic, which helps inhibit mold.
- Vermiculite: This mineral is excellent for maintaining a steady moisture level and is very clean to work with.
- Wood Shavings: Often sold as pet bedding, these are inexpensive and provide great air circulation. Avoid cedar shavings, as the oils can be harsh on the tubers.
- Dry Sand: Sand is heavy but very effective at keeping temperatures stable.
The Storage Container
We recommend using containers that allow for a tiny bit of air exchange. Plastic bins with several small holes drilled in the sides are excellent. Cardboard boxes also work well, though they can sometimes draw moisture away from the tubers if the air is very dry.
Place a layer of your chosen packing material in the bottom of the container. Nestle the tubers or clumps inside, making sure they are not touching each other. Cover them completely with more material. This prevents a single rotten tuber from spreading its problems to its neighbors.
Finding the Right Storage Location
Location is everything when it comes to wintering dahlias. The ideal storage temperature is between 40°F and 50°F. This range is cool enough to keep the plants dormant but warm enough to prevent freezing.
The Ideal Spot
An unheated basement, a crawl space, or a cool closet in a mudroom are often the best spots. If you use a garage, be careful. Most attached garages stay warm enough, but a detached garage can easily drop below freezing during a cold snap. A simple thermometer can help you monitor the temperature over a few days before you commit to a spot.
Places to Avoid
Avoid storing your tubers near a furnace or a water heater. The heat will dry them out quickly, and the temperature fluctuations can cause them to wake up from dormancy too early. Likewise, avoid the very back of a refrigerator unless you are sure it stays above 40°F. Most home refrigerators are set to 35°F, which is too cold for long-term dahlia health.
Winter Maintenance and Troubleshooting
Your job is not quite done once the tubers are packed away. It is important to check on your dahlias once a month throughout the winter. This allows you to catch small issues before they become big problems.
What to Look For
When you open your storage bins, look for two things: shriveling and mold.
If the tubers look wrinkled and feel soft like a sponge, they are too dry. Use a spray bottle to lightly mist the packing material with water. You do not want it to be wet, just slightly damp to the touch. This will help the tubers rehydrate.
If you see fuzzy white or green growth, the tubers are too wet. Remove any tubers that have become soft or "mushy." These cannot be saved and will only rot the others. Leave the bin open for a day or two to let some of the excess moisture evaporate, or replace the packing material with fresh, dry material.
Handling Rot
If you find a small spot of rot on a large, healthy tuber, you can often save it. Use a clean knife to cut away the rotten portion until you see clean, white flesh. Dust the cut end with a little bit of cinnamon (a natural antifungal) or sulfur powder and let it dry before putting it back in storage. If you need help with an order issue, our 100% Quality Guarantee explains how we make it right.
Overwintering in the Ground
If you live in USDA zones 7, 8, or 9, you might be able to leave your dahlias in the garden. This is much less work, but it does come with some risks. Success depends largely on how well your soil drains.
Protecting In-Ground Tubers
In these warmer regions, the goal is to keep the frost from reaching the tubers and to keep the soil as dry as possible. After the first frost, cut the stems down to the ground. Cover the entire area with a thick "blanket" of mulch. Use 6 to 12 inches of straw, wood chips, or shredded leaves.
Some gardeners also place a piece of plastic or an old tarp over the mulch to deflect winter rain. If the tubers sit in cold, saturated soil for months, they are very likely to rot, even if the temperature stays above freezing. In the spring, wait until the soil begins to warm up before pulling back the mulch to let the new shoots emerge.
Preparing for Spring
As the days get longer in March and April, your dahlias will naturally begin to "wake up." You may see small pink or white sprouts starting to emerge from the crowns of your tubers. This is an exciting sign that your wintering efforts have been successful!
Wait until the danger of frost has passed and the soil temperature reaches about 60°F before planting them back outside. If you are eager for early blooms, you can pot up your tubers indoors about four to six weeks before the last frost. This gives them a head start so they are ready to grow vigorously as soon as they hit the garden soil. For another big-blooming option, browse Dahlia Dinnerplate High Summer Mix.
We believe that gardening should be a cycle of joy rather than a source of stress. While it takes a little effort to winter your dahlia bulbs, the reward is a garden that grows more beautiful and meaningful every year. Each tuber you save is a piece of your garden's history.
Conclusion
Learning how to winter dahlia bulbs is a fundamental skill for anyone who loves these vibrant flowers. By following the simple steps of waiting for the first frost, lifting carefully, and storing at the right temperature, you ensure your garden stays full of color year after year. Whether you choose to store whole clumps or divide them for more plants, the process is accessible for gardeners of all experience levels.
- Wait for the first frost to trigger dormancy.
- Dig carefully to protect the fragile necks of the tubers.
- Cure the tubers for a few days before packing them in a medium like peat moss.
- Store in a cool, dark place between 40°F and 50°F.
- Check monthly for moisture levels and signs of rot.
Key Takeaway: Consistent temperature and a slight amount of moisture are the two most important factors for keeping your dahlia tubers healthy until spring.
We are here to help you grow the garden of your dreams. If you're looking to expand your collection with new and exciting varieties, explore Dahlia Dinnerplate Summer Lovin Collection and find your next favorite bloom.
FAQ
Should I wash my dahlia tubers before storing them?
Yes, washing tubers is generally recommended for home gardeners. It removes soil-borne pathogens and makes it much easier to inspect the tubers for rot or damage. Just be sure to let them dry thoroughly for a day or two so no standing water is trapped in the hollow stems.
Can I store dahlia tubers in the refrigerator?
While it is possible, most home refrigerators are a few degrees too cold (usually around 35°F to 37°F). Dahlias prefer a temperature between 40°F and 50°F. If you have a dedicated beverage cooler or a temperature-controlled cellar, those are much better options for maintaining the correct range. For shipping timing details, see our Shipping Information.
What happens if I don't dig up my dahlias in the winter?
If you live in USDA zone 7 or colder, the tubers will likely freeze and turn to mush once the ground temperatures drop. In warmer zones, they may survive if the soil stays dry, but they are prone to rotting in wet winter conditions. Digging them up is the safest way to ensure they return.
How do I know if a tuber is dead in the spring?
A healthy tuber should feel firm, similar to a fresh potato. If the tuber is shriveled and dry like a twig, or if it is soft and oozing, it is no longer viable. You should also look for an "eye" near the stem; if the tuber has no growth point, it will not produce a new plant.
