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How to over winter dahlia tubers


How to Overwinter Dahlias

Dahlias are at their best in late summer and fall, when the plants are mature and pumping out tons of blooms. But before the first frost, you have a decision to make. Will you treat your dahlias as annuals and plant a fresh batch of tubers next spring, or save the tubers from your favorite varieties and grow them again next year? If you want to try your hand at overwintering some tubers, read on for step-by-step instructions.

To Dig or Not to Dig

Dahlias are are warm climate plants and they do not tolerate freezing temperatures. If you live in hardiness zones 8-10, where winter temperatures rarely fall below 20° F, the soil provides enough insulation to protect the tubers and it's safe to leave them right in the ground. In late fall, simply cut the plants back to several inches above soil level. They will start growing again in spring.

Dahlia tubers may survive a mild winter outdoors in zone 7 (as long as the soil is well drained and the area is thickly mulched). But in most of zone 7 and in all of zones 3-6, dahlia tubers must be dug up and stored indoors.

For this task you need pruning shears, a shovel or digging fork, survey tape and marker, damp growing mix, and either big nursery pots, black plastic trash bags, paper bags or large boxes. Here's how to do it:

How to Dig and Store the Tubers

1. LABEL. Start by labeling your plants with survey tape (plastic plant labels are too easily lost). Be sure to do this BEFORE you get a frost so you can still see the flowers and evaluate which plants you want to keep. Save only the plants that are strong and healthy, and that really impressed you. There are tons of great dahlias out there and no reason to grow underwhelming ones.

2. CUT BACK. After the first hard frost, try to leave the tubers in the ground for a week or two. While waiting isn't essential, it does help to toughen the skin of the tubers. Don't cut down the plants until right before you dig them. This way water won't accumulate in the hollow stems. When you're ready to dig, cut back all of the stems to within 3-4” of the ground. Re-tie the labels as needed, so they are securely attached. If your dahlias were grown in containers, skip down to the section on packing and storage.

3. DIG. Dig up each root ball, starting at least a foot away from the stem. Depending on the size of the plant, the root ball may be 12” to 18” across and equally deep. Go slowly and be gentle, as the tubers are extremely brittle. During storage, damaged tubers are more susceptible to decay.

4. DRY. If possible, let the clumps air dry for a day or two. But make sure they are protected from frost. Tubers may be divided at this point, or you can wait and do it during the winter or early next spring. If you plan to divide your tubers later, there's no need to wash soil off the clumps. Just store the entire root ball as it came out of the ground. The soil gives them some natural protection from damage and rot. If you want to divide the tubers now (which will save on space if that's an issue) skip ahead to the dividing instructions below.

Packing and Storing Your Dahlias

5. PACK. If you are not dividing the root balls until spring, you can store them in several ways. You can put them in large nursery pots with barely damp potting soil. Or store them in ventilated cardboard boxes or large plastic storage tubs that are partially filled with growing mix, peat moss or vermiculite. Another option is to store several clumps together in a large black plastic trash bag.

Once your dahlias are in storage, the goal is to retain enough moisture to prevent the tubers from shriveling, but allow enough air circulation to avoid rot. This means keeping the tops of the storage tubs or plastic bags loose. The humidity level in your storage area makes a difference, so it may take a few seasons to arrive at the best solution. If the storage area is relatively humid, start with paper bags and boxes. If dry, go with tubs or plastic bags.

6. STORE. Store the pots, boxes or bags in a cool, dark, humid place where the temperature will stay between 40 and 50 degrees F. An unheated basement works well in the coldest climates. In zones 5 and 6 you may be able to keep them in an attached garage. Just make sure there's no chance that the tubers will freeze. A frozen tuber is a dead tuber.

 7. CHECK. Check on your dahlias periodically through the winter. If the storage conditions are too moist, you may get some mushy tubers. Remove them and increase the ventilation to reduce moisture levels. If the tubers are wrinkled and dry, mist them or add some damp growing mix to help them rehydrate.

Tips for Dividing and Replanting

In late winter or very early spring, pull out your dahlias and discard any tubers that are soft or have completely dried out. Then it's time to start dividing the root balls into manageable-sized clumps. If you want to skip dividing and simply replant an entire clump, go ahead. Otherwise, read on.

When dividing a clump of dahlia tubers, each division must wind up with one or more growth eyes. These eyes occur in a very specific location. In the photo below, some of the eyes have begun to sprout, so it's easy to see how they are clustered on the knobby part where the tuber is attached to the stem. No matter how good a tuber looks, if it doesn't have at least one eye, it will not grow a plant.

It takes practice to see the eyes, and dividing clumps of tubers can be intimidating. If you wait until early spring, some of the eyes will start to swell and sprout. This makes it easier to see where to make the cuts. To be on the safe side, you can simply divide large root balls into halves or quarters. Cut down through the middle of the clump, making sure to leave some of last year’s stem attached to each division.

To learn more, you can watch this video on our YouTube channel: How to Overwinter Dahlia Tubers, or read some of the following articles on our website: All About Dahlias, How to Pinch and Stake Dahlias, How to Plant Dahlias (video), and Dahlias: 8 Great Looks.

Learn More:

How to Overwinter Dahlia Tubers

By

David Beaulieu

David Beaulieu

David Beaulieu is a landscaping expert and plant photographer, with 20 years of experience. He was in the nursery business for over a decade, working with a large variety of plants. David has been interviewed by numerous newspapers and national U.S. magazines, such as Woman's World and American Way.

Learn more about The Spruce's Editorial Process

Updated on 02/22/22

Reviewed by

Debra LaGattuta

Reviewed by Debra LaGattuta

Debra LaGattuta is a gardening expert with three decades of experience in perennial and flowering plants, container gardening, and raised bed vegetable gardening. She is a Master Gardener and lead gardener in a Plant-A-Row, which is a program that offers thousands of pounds of organically-grown vegetables to local food banks. Debra is a member of The Spruce Gardening and Plant Care Review Board.

Learn more about The Spruce's Review Board

The Spruce / Ellen Lindner

Project Overview

Dahlias are subtropical plants native to Central America, and gardeners all over the world grow them for their colorful, diverse, and spectacular blooms.

The secret to successfully growing dahlias in cooler climates lies underground in their tubers. During the growing season, each dahlia plant produces a clump of tubers up to six inches deep underground. Dahlia tubers, which look somewhat like a small sweet potato, are swollen underground stems that store energy to enable plant growth the following spring.

Dahlia tubers are not true bulbs. Bulbs are round and consist of one swollen root while dahlia tubers are food storage vessels that come in various shapes and sizes and form a clump. Bulbs differ from tubers because bulbs contain the embryo of next year's blooms while dahlia foliage is produced from eyes located in the crown of last year's plant.

Because dahlias are hardy only to USDA hardiness zone 9, gardeners in colder climates must dig up dahlia tubers before the first autumn frost and overwinter the tubers indoors and replant them in the spring.

Steven Nadin/EyeEm/Getty Images

14 Gorgeous Must-Plant Dahlias

When to Dig Up Dahlia Tubers

Mother Nature will alert you when it's time to dig up your dahlia tubers. Dahlia foliage cannot tolerate freezing temperatures. The first heavy frost will blacken and turn to mush the flowers, stalks, and foliage.  However, deep underground the tubers are still alive and waiting for you to dig and store them for the winter.

Don't be too hasty and dig your tubers before the first frost. Frost stimulates dahlia tubers to set eyes for next year. Wait for 10 to 14 days after the first frost to dig up the tubers, but make sure to dig them up well before a hard freeze is expected. 

Tip

Before the first frost hits is a good time to affix a label to the base of the dahlia stalks so that you'll be able to identify the variety next season when you re-plant the tubers.

Equipment / Tools

Materials

  1. Cut down the Dahlia

    As soon as the first autumn frost blackens the dahlia foliage, cut down the dahlia stalks to a few inches and wait at least 10 days before digging up the tubers.

  2. Dig Up the Tubers

    After waiting at least 10 days after you cut back the blackened foliage, loosen the soil around all four sides of the dahlia by gently angling and pushing the garden fork or shovel into the soil about a foot away from the main stalk. Be careful not to let tools come in contact with the tubers, which are easily damaged. Gingerly pry up the soil as you go, freeing the tubers. With one hand on the stem and the other under the clump of tubers, carefully lift and remove the entire tuber clump.  

  3. Inspect, Clean, and Prune the Tubers

    Inspect your dahlia tubers and trim away any tubers or tuber parts that are rotten or damaged. Don’t save every tuber, save only tubers that are in good condition.  Clean off most of the soil and trim back the roots.

    It's important to remove and discard the mother tuber—it's located in the center part of the structure. The mother tuber will look different; it has a more crinkly texture and is darker than the other tubers. The mother tuber produced the plant this year and won’t have any more energy left for next year. In the case of first-year plants, this is the original tuber that you bought and planted. The mother tuber is more likely to rot and could spread to the other tubers in storage.

  4. Divide the Crown into Individual Tubers

    You might want to divide the tubers before you dry them for storage rather than waiting until spring. Dividing a tuber clump is an optional step; it is perfectly fine to store the entire tuber clump as one unit.

    Dividing means cutting apart the crown and retaining one or more tubers along with it. The crown is located at the base of the stem, and it contains the eyes where new growth emerges. To produce a plant next year, each division must have a piece of the crown that contains at least one or two eyes. You can usually assume that if you have a big piece of crown, it has an eye

    Let the tuber divisions sit for a day or so to allow the cuts to callous over.

    Tip

    Sometimes the eyes, which is where new growth emerges, don't appear until after the winter storage period. In this case, it can be more time-efficient to wait until spring to divide the tubers. 

    Dividing a tuber clump is optional, and it's worth noting that storing and replanting an entire clump of tubers could offer a higher chance of success next year because you preserved the entire crown, which contains multiple eyes.

  5. Hang the Tubers to Cure

    Hang the tubers upside down with twine and allow them to cure out of direct sunlight for two weeks. Only cure them outdoors if temperatures are above freezing. If rain is forecasted, move the tubers indoors to a location that does not receive direct sunlight. Otherwise, cure them indoors in a cool and dry location, perhaps a garage, shed, or basement.

    Once the dahlia tubers are dry, use pruners to remove most of the remaining stalk.

  6. Apply Sulfur to the Tubers

    To prevent rot and deter fungus during the overwintering process, many gardeners opt to sprinkle sulfur dust (a type of fungicide) onto tubers before storage. Come spring, you can plant the tubers, dust and all, to continue to thwart decay before they sprout.

    Protect yourself from the sulfur dust by wearing long pants, a long-sleeve shirt, a dust mask, and gloves. Sprinkle the tubers liberally with sulfur dust. Take care to apply the powder to any areas that are nicked or cut.

  7. Prepare the Storage Box

    Line the bottom of a cardboard box with newspaper to cover any cracks. Pour in two inches of peat moss. Use a spray bottle to slightly moisten the peat moss. Make sure not to saturate the peat moss, which can cause tubers to rot. Instead, strike a balance between dry and wet, erring on the side of dry.

    Storage medium

    Tuber storage medium is a matter of debate. Instead of peat moss, some gardeners opt to use vermiculite or even dry sawdust as their tuber storage medium. Other gardeners individually wrap each tuber in newspaper. Still others wrap tubers in plastic wrap. The point is that there is no single answer for storage medium and methods. You need to experiment with what storage process is successful for you year to year.

  8. Place Tubers in the Storage Box and Store in a Cool, Dry Place

    Lay the tubers flat on the peat moss, and then cover them with an additional inch of peat moss. Make sure tubers or tuber clumps are not touching one another. You can place dry sheets of newspaper between layers of tubers.

    Store the box in a dark area—such as a basement, garage, or root cellar—that will remain cool for the winter but will not freeze. The ideal storage temperature is above freezing but below 50 degrees Fahrenheit.

  9. Check the Tubers Periodically

    Periodically check your tubers during the winter. If they seem overly dry, spritz the peat moss with a spray bottle. And if a tuber feels mushy, discard the rotten culprit before it infects the rest of the tubers.

Tips for Overwintering Dahlia Tubers

Experiment with your storage methods until you find an overwintering system that works best. This might mean wrapping your dahlia tubers in newspaper to soak up excess moisture before storing them or opting to store them in paper bags or milk crates instead of a cardboard box.

You can add peat moss to a zippered bag, place the dried tubers into the bag, add a liberal sprinkling of sulfur dust, seal the bag, and then gently shake it to distribute the dust. Then, the tubers are ready to be stored.

Before foliage is blackened by frost, label the dahlias if you grow different varieties, so you know which cultivars you're working with when spring rolls around. You might even consider using separate storage boxes for each dahlia variety.

How to Grow and Care for Dahlias

Article Sources

The Spruce uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.

  1. Digging, Dividing, and Storing Tubers. The American Dahlia Society Website

digging, processing, marking, rules and optimal storage conditions in the basement, apartment

Many gardeners with the onset of autumn are wondering how to keep dahlias in the winter at home. The tender tubers of these plants will not survive frosts in the ground, and therefore they will need to be moved indoors before the cold weather. Storing dahlias in winter is a responsible and important matter for those who are used to enjoying gorgeous flowers on their backyard every year and want to help them stay as decorative as possible. nine0003

Contents

Preparing for Home Storage: Process Details

It is necessary to start preparing for wintering before the onset of autumn frosts, which are extremely dangerous for dahlias. Both the ground part and the roots of dahlias are affected during frosts, so such spoiled material for planting no longer survives until spring. In order for dahlias to calmly overwinter the first frosts, you need to insulate them in advance by spudding the bushes like potatoes. nine0003

You need to focus on the weather. As soon as the first frost touches the ground part of the dahlias, the foliage will turn black and dry. For the gardener, this is a signal: it's time to start digging up the tubers. To begin with, with a sharp tool, you need to carefully cut the stems, leaving no more than 5-10 cm to the tuber. Labels with the name of the variety can be attached to these “stumps”, so that in the future it will be more convenient to arrange storage. After cutting the stems, if there is no precipitation and is not expected in the near future, the tubers can stay in the ground for another week .

How to dig up tubers

To store dahlias in the winter in the basement or in the apartment, after trimming the stems, you will need to properly prepare them for future holidays. Dahlia tubers will need to be dug up, cleaned of soil, dried and stored.

It will be most convenient to dig out according to the following scheme:

  1. Dig up the overgrown tubers at a distance of about 20 cm from the "stumps" in a circle.
  2. Digging will be more convenient if you lift each root with a pitchfork or a shovel, in no case pulling them out of the ground by cutting stems. nine0008
  3. Rinse each tuber, washing off the soil with a strong jet from a hose or watering can.
  4. Treat the roots with a weak solution of manganese.
  5. Cut off damaged areas, as well as small nodules, sprinkling the cut areas with ash or coal. You can, if necessary, process sections with brilliant green. Next, cleaning and storage of dahlias in the cellar or basement is organized.

After all the manipulations, it remains to dry the tubers. For this, dry living rooms are not suitable, in which the delicate planting material will instantly dry out. Ideal conditions for this are on the balcony, veranda or in the greenhouse. In 3-5 days, the tubers will dry out, and they can be removed for final winter storage in the basement, checking the readiness on a dry surface. nine0003

Pretreatment of bulbs before spring

Harvesting and winter storage of dahlias in the cellar will not be possible unless the tubers are treated with a fungicide or sulfur. This will prevent the spread of various pathogenic bacteria that can kill plants. This procedure can be carried out in different ways: either powder the tubers in a dry form, or prepare a solution of the drug, where all the roots are completely lowered one after another.

The likelihood of spreading diseases between tubers is negligible with this sequential treatment. The main thing is to keep each variety in liquid for about 15 minutes. After that, the tubers need to be dried by laying out on a plank, cardboard or newspaper folded in several layers. It is more convenient to do this by laying tubers according to varieties, so as not to confuse them in the future. nine0003

Processing features:

  1. How do you keep dahlia tubers from rotting? To increase the effect, you can add a systemic insecticide to the treatment composition.
  2. Use only rubber gloves to protect hands from chemical burns.
  3. It would be more correct for each variety to prepare its own container, signing it in advance.
  4. Dahlia tubers that do not sink, but float on the surface, should be discarded, they will not survive until next year. nine0008
  5. It is better not to spread dahlia roots on concrete surfaces, as they will shrivel and dry out due to high humidity.

A number of gardeners increase the processing time of dahlias to 30 minutes, while others do not use fungicides at all. Ultimately, the opinion of each individual gardener is decisive. You can be guided by the fact that for a humid climate, the treatment will be uniquely useful, since the atmosphere itself is conducive to the emergence and development of various fungi even before the onset of spring. nine0003

Tuber marking before spring

The last stage of preparations is the marking of dahlia varieties. You should write the maximum amount of information required so that after a year you do not confuse the varieties. It is best to write the names in full or make a code plate if you can guarantee that it will not get lost. It will also be useful to additionally mark with a tick or an asterisk the tubers of the most robust plants, especially if many belong to the same variety. In the spring, this will help to find the highest quality planting material and use it for cuttings. nine0003

Inscriptions can be done with an ordinary indelible pencil, it will cope with the work even on dahlias that are not completely dry. If the pencil does not write well, it will need to be moistened in a jar of water, but in no case should you do this with saliva, taking the writing device in your mouth. It contains extremely harmful and toxic elements. You can use a thin marker, ideally take a new one that writes well on any surface.

How to save dahlias in winter (video)

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How to store dahlia tubers in winter: options and necessary conditions in the cellar, in the basement of a city apartment

The easiest way to store tubers is on racks. It will be necessary to pour sand on the shelves in an even layer and place boxes with dahlias on it. The roots of the tubers will need to be tied with bags filled with vermiculite. More experienced gardeners can use moss. Tubers are wrapped in it and covered with polyethylene so that moisture does not evaporate.

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The main difficulty is a sufficient degree of moisture content of the moss, because if it dries out, it will begin to feed on moisture from the plant, and if it is too wet, it will cause the tubers to rot.

If the boxes are to be stored in a cellar or cellar, they must be prepared as follows:

Alternative storage methods:

  1. How to keep the tubers until spring so that they do not rot? Pre-treat them with a clay mash from ordinary red clay mixed with blue vitriol and manganese. Each tuber is dipped into the mixture separately, dried and placed in a bag. Then they are cleaned in boxes prepared according to the already indicated scheme. nine0008
  2. Soak the tubers in liquid hot paraffin (each separately), let cool, wrap in cling film and paper, and then place in a box. In the spring, before planting, the paraffin will need to be removed. This method is best suited for early varieties.

Methods for proper storage of roots indoors: at what temperature

It will be more difficult to figure out how to store tubers in an apartment due to the fact that there is no way to maintain ideal conditions for them, and there is usually not so much space in living quarters. nine0003

However, gardeners have come up with several reliable options:

  1. Wrap the tubers in perforated polyethylene bags filled with dry brown peat. Sphagnum is also suitable. Remove the roots in a film in a relatively cold and dry place. A pantry, a threshold of a loggia, a closet are suitable for placement. When organizing the storage of dahlia tubers, it is important to periodically check their appearance and general condition.
  2. Dust the tubers with ash, put them in whole plastic bags, let them fill with air and tie, then send them to a cool place. nine0008
  3. A small number of tubers can be sent to the refrigerator, but such storage of dahlias is not always appropriate, since there is not enough space for them.

Trying to keep dahlias in the apartment should be only if there is no way to put them in the winter in the basement or other unheated room, where the microclimate is more suitable for plants. Having understood how to store dahlia tubers in winter, amateur gardeners will be provided every season with flower beds of stunning beauty with bright large flowers. nine0003

Digging, storage of dahlias (video)

When to dig up dahlias and how to store tubers in winter at home

Dahlia is a favorite of many gardeners, its luxurious flowers of different shapes and shades can decorate any area. Despite the fact that the plant is native to South America, keeping dahlias for the winter is not difficult if you create the right conditions.

In order for dahlias to bloom in the new season, it is important to arrange a warm winter for the tubers. You can’t leave them in the soil, because. after the first severe cold, the plants turn black and die. nine0003

In August, when dahlias are in full bloom, you need to stop feeding, providing the plants with rest. Just at this time, the formation of tubers and their storage of nutrients begins.

Autumn care for dahlias - preparation for winter

Now let's figure out how to prepare dahlias for winter. In early September, the bushes need to be fairly high up (approximately 8-12 cm high). This will make them more resistant to wind and cover the base of the trunk, which means that the tubers will grow strong. In general, the procedure can be carried out at the end of summer. nine0003

Dahlias should be watered sparingly so that excess moisture does not lead to infection. Weak stems without buds, lower leaves, as well as drying flowers should be cut off to speed up the formation of new buds.

When to dig up dahlias

Dahlias are dug up in the middle lane and Moscow region in mid-late October, depending on the weather. It’s good when, by the time of digging, the heaped tubers have already withstood several weak frosts - this will harden them and help them to endure wintering at home without any problems. nine0003

So how do you keep dahlias in winter? First of all, cut off all the stems with secateurs, leaving stumps 10-15 cm high. If you cut the stems lower, there is a danger of infection entering the tubers. Also, if the height of the “hemp” is insufficient, water can flow into the tubers, and they simply begin to rot.

Then carefully loosen the shrub and dig in with a fork to loosen the surrounding soil. It is also better to raise the dahlia with a pitchfork, trying not to pull the stems. If the weather permits, then the dug tubers can be left to dry in the garden for several hours, after which the earth must be shaken off and the tubers themselves carefully examined. nine0003

Weak and diseased tubers are discarded and strong tubers are thoroughly washed with water. Cut long roots with scissors

It is better to divide the tubers strictly before planting, otherwise they will lose a lot of moisture during the winter.

Treatment of dahlia tubers before winter storage

To prevent diseases, treat washed dahlia tubers with a fungicide, such as Fitosporin. Prepare the solution according to the instructions and soak the tubers in it for about an hour. Instead of fungicides, you can also use a pink solution of potassium permanganate. Keep the tubers in it for about 30 minutes. nine0003

Then tag the tubers with variety names. If the variety is unknown, you can focus on the size of the bush, the shape or color of the flowers.

The next step in preparing dahlias for winter is drying the tubers. To do this, you need to choose a dark, cool place and put the bushes with the tubers up so that the moisture accumulated in the stems flows out and the tubers do not subsequently rot.

How to store dahlias in winter at home

Dried dahlia tubers are placed tightly in plastic buckets or boxes and covered with dry sand or sawdust, leaving the tops of the stems with tags uncovered. To prevent sand from spilling out of the box, you can lay a bag of sugar on the bottom, and then lay out a layer of newspapers. nine0003

Gardeners differ a little on how to preserve dahlia tubers, with some using wet sand instead of dry sand. Everything is individual here, and if the tubers were dug out in dry weather, and then not soaked in a fungicide solution, then sand or sawdust is really better to moisten.

There are several other ways to store dahlia tubers in the winter:

How to keep dahlias until spring? Choosing a storage location

The optimum temperature for storing dahlias in winter is 3-6°C, humidity is 60-70%. At lower temperatures, the tubers will freeze, at high temperatures, they will begin to germinate. There are several places where plants will feel comfortable until spring. nine0003

Cellars and cellars . They are characterized by high humidity and low temperature. The tubers will not suffer from drying out and will not germinate ahead of time. This is the best place to store dahlias!

Subcol . Here, the humidity is lower than in the basement, and the temperature can be slightly higher, often there is stagnation of air. Therefore, it is recommended to turn on the fan in the room several times a week.

Refrigerator . A suitable place for a small number of dahlias. Put the tubers in a perforated bag and cover with sawdust. Check regularly for rotting. For storage, the lower or middle shelf is suitable, as well as a compartment for vegetables. nine0003

Glazed balcony . Choose the darkest place and put a box of tubers in it. If the temperature starts to drop, cover the crate with old blankets or clothes. In frost, it is better to transfer the tubers to the room for a while.

Periodically check the tubers for signs of decay.

Protect the dahlias from being eaten by rodents. It is better to use fast-acting poison baits or ultrasonic repellers. There is evidence that mice and rats do not tolerate peppermint essential oil.

Learn more