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How to over winter dahlia bulbs


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.

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How to Overwinter Dahlia Tubers

By

David Beaulieu

David Beaulieu

David Beaulieu is a landscaping expert and plant photographer, with 20 years of experience.

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

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

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. To scare away, soak paper napkins with oil, put in glass jars without lids and place them in different corners of the room or near boxes with tubers. Once a week, change the napkins for new ones. nine0003

Is it possible not to dig up dahlias for the winter

Novice flower growers often ask themselves the question: is it necessary to dig up dahlias for the winter, is there any way to avoid this troublesome procedure? Unfortunately, these plants are very afraid of the cold and will not survive until spring. But there is a way out. If storing dahlias in winter is problematic for you, grow them as annuals. Or you can dig up only the most beloved and expensive varieties, and re-plant the rest in the spring. The decision is yours! nine0003

Storage of dahlia tubers is not difficult, but responsible, because you need to look after the "wintering" plant: check the tubers, regulate the temperature regime. The dahlia will not remain in debt, but will delight you with its lush bright flowering!

Articles you might also be interested in:

How to store dahlias in winter? | Interesting facts

Many gardeners consider these plants unpretentious. Indeed, because dahlias feel good even on rather poor soils, they delight with a variety of shapes and colors, as well as luxurious long-term flowering. The difficulty is the storage of tubers in the winter.

Dahlias - magnificent flowers

When to dig up dahlias

Dahlias are perennial flowers, in warm climates they successfully overwinter in the soil, but Russian harsh winters can kill plants. Nevertheless, luxurious varieties of dahlias, such as spherical, pompon, anemone, need to be dug up for the winter. nine0003

Low-growing varieties can be transplanted into pots and enjoy flowering

How not to miss this moment? Very often summer residents complain that with the onset of cold weather, dahlias bloomed even more magnificently and more beautifully. You should not hurry with the digging procedure, even if autumn is in full swing outside the window. If frosts are expected, there is a risk of losing plants.

When to dig up dahlias. Diseases of dahlias

September-October is an active time for budding in dahlias. You can notice the formation of tubers even at the very beginning of flowering, but their full ripening occurs precisely in autumn, so it is recommended to leave dahlias in the ground as long as possible, while you should follow the weather forecast. nine0003

Dahlias are dug up after the first hard frost. It will not be superfluous to spud dahlias, insulating them with a ground "blanket", which will keep the flower from the first cold weather. Dig up flowers after the first frost, when they wither. It is recommended to cope with this work no later than 3 days after the arrival of cold weather. The same rules work for gladioli.

How to properly dig up dahlias

If your garden has flowers of different varieties, it is advisable to attach name tags to the stems. This will greatly simplify your task when planting plants, and you can easily decorate the cottage by planting plants according to their colors. nine0003

How to properly dig up dahlias

Just before digging, cut the stems, 10-15 cm long will be enough. It would not be superfluous to cover the sections with foil or cellophane to prevent the stem from rotting in case of precipitation. Do not forget that the root collar of dahlias is very fragile. An ordinary break will not disappear without a trace - such tubers will not overwinter.

After cutting the stems, dig the soil around the plant, choosing a radius of about 30 cm. It is better to use a pitchfork instead of a shovel. This can significantly reduce the risk of damage to tubers. After digging, carefully remove excess soil, especially care should be taken at the root neck of dahlias. nine0003

How to prepare for storage

The dug up tubers require a bit of work:

1. Do not grab the plants by the stems to avoid damaging the neck.

2. If the weather is sunny, leave the tubers in the garden for a few hours. During this time, they will harden well and become stronger.

Thin roots are trimmed

3. The next procedure is washing the tubers. It will be convenient to use a regular hose for watering the garden or washing the car. A good pressure will remove all the earth, and dahlia tubers can be easily examined for disease. nine0003

4. Minor damage is simply cut out and covered with wood ash. If the plant is badly damaged (gray rot, fusarium, nematodes, greenhouse whitefly), discard it. Otherwise, there is a risk of losing healthy flowers.

5. In the process, you can trim the thin roots a little, this will not hurt. This procedure does not hurt to do in the spring just before planting flowers.

The roots are kept in the air so that their skin becomes coarse

6. Good results are obtained by special treatment of tubers: fundozol is diluted and the tubers are sprayed. Next, you should wait until the skin of the plants hardens. This may take up to 5-6 days, but will extend the shelf life. nine0003

How to store dahlias in the cellar

Some of the most beautiful flowers in your flower bed will delight you year after year if they are properly stored. The cellar is an ideal place for this task, but there are several conditions:

- it must be insulated and not freeze;

- you need to find a place away from potatoes;

- make sure the room is free of rodents.

How to store dahlias in winter

Prepare storage containers - boxes, boxes, soil. Pour the tubers with sawdust. If possible, use conifers. Ordinary sand will do. Plants can be laid in several rows, but the fewer, the better. nine0003

To prevent the tubers from drying out, they are covered with sawdust, pine needles or sand.

During the winter, dahlias can rot, freeze, dry out. Premature germination is also a problem. Therefore, from time to time you need to go down to the cellar and check your favorite flowers. Once a month will be enough.

It is easier to store dahlias in a warm cellar than in an apartment. Such a "treatment" can be done with any other fungicide. The sand or sawdust that covered the affected dahlia is replaced with new ones. Do not forget about the ventilation of the cellar - the air where the plants are stored should not be stale. nine0003

How to store dahlias in winter at home

Dahlias are excellent flowers for birthdays, weddings, women's holidays, they are an ideal present for mother, wife, daughter. But in order for them to survive until the event, reborn after wintering, city dwellers have to invent different ways of storage. One option is to put flowers for the winter right next to the balcony door. A dry basement is also suitable, where the temperature is guaranteed to be 2-5 degrees, and the humidity does not exceed 60%.

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