Dahlias are a favourite amongst gardeners for their beautiful colouring and easy growth and have been a popular planting and potting choice in UK gardens over the decades. These colourful and bright flowers are perennials and, if the plants are treated properly, you can decorate your garden year after year with their late summer blooms. But you may be wondering how to store dahlias over winter so you can enjoy these botanic beauties for another year. If you have potted dahlias, you will find that keeping these plants protected is actually pretty easy and requires little effort. Below we will take a look at what you need to do to make sure that your dahlia’s in pots survive the colder months and grow again in your garden the next year.

Dahlia and mixed flowers in pots
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Are Dahlias Hardy?

Although dahlias are perennials and relatively easy to care for during the warmer months, they are not particularly hardy and don’t do well with frost. So, there are some steps you should take if you are looking to overwinter dahlias in pots, but you will find that it is definitely worth the effort and will save you money on having to buy new plants when the next spring rolls around.

Potted Dahlia
Potted Dahlia

How to Overwinter Dahlias in Pots?

One of the best things about growing dahlias in pots is the flexibility it offers you in terms of moving them around as the weather changes. You can move them around the garden during the summer to ensure the best blooms and easily move them into more protected areas for winter storage as the temperature drops. Keeping your dahlias in pots means that you don’t have to dig up your dahlias and store them. Instead, you can just move the planter into a safe place that will protect the plants during a chilly winter.

In order to best ensure the health of your dahlias during freezing temperatures, you will have to try to recreate the environment which is similar to that that dahlia tubers experience in drier climates where they don’t have to deal with ground freezes.

What You Need

  • Pick a suitable location to move the pots
  • Frost Fleece Material
  • Gardening shears

Step 1 – Select Where You Will Move Your Pots

Your first task is to decide where you will store your dahlia pots. You should move them to cool dark and dry spots such as a shed, garage, or greenhouse where they will be protected from frost and rainfall.

You can also choose to cover your pot with a frost fleece (Amazon link – opens in a new tab) to help protect it against very cold temperatures even when it is inside.

Step 2 – Cut Back Your Dahlia Plants for Overwintering

Then to get them ready for the months ahead, just before the first frost, you should cut the dahlia stems back with your gardening shears, so the plant is down to a few inches from soil level.

Your goal is to get the plants in the right dormant state so they will be best placed to survive the cold ahead.

Step 3 – Allow Your Dahlia Pots to Dry Out a Little

Once you have decided where you are going to store your dahlia pots over winter, your next step is to allow the pot to dry out a little. Turn the pots on their sides to facilitate the drying-out process. You should not let them dry out completely, but you do not want them to be too damp. And you will not need to water them as often as you have been during the summer months. A cup of water once a month should be sufficient for dahlias in water that are being kept undercover and indoors.

As the month passes, make sure to do regular checks on the health of the plant and check for any rotting or dead stems you need to remove to protect the rest of the plant.

Step 4 – Place Your Dahlias in a Greenhouse

If you have been keeping your dahlia pots in a shed or garage during the winter months, as the spring approaches you can move your pots to your greenhouse or shed. This gives them an earlier exposure to light and ensures earlier growth.

If you don’t have access to a greenhouse or conservatory, then make sure that you wait until the final frost has passed before you move your dahlia pots back out.

Step 5 – Put Your Pots Out Again for the Summer

Once the final frost has passed you can start to place your pots out in the garden again ready for the new year’s growth. Start to rehydrate the plants if they have shrivelled, but make sure not to overwater. You should start to see your dahlias bloom again in mid-summer, around the middle of July.

Dahlia Pom Pom Flower Head
Dahlia Pom Pom Flower Head

My Experiment with Overwintering Dahlias

A good long time ago when I was a much younger man, I was told of a few ways to overwinter dahlias so decided to conduct a little experiment for myself.

The Setup

Pot 1 – Left in Place: This dahlia was left right where it was, exposed to the elements throughout the winter.

Pot 2 – Brought Inside: Initially, this dahlia was brought inside to protect it from the winter chill. As early spring approached, I moved it to a greenhouse, hoping the controlled environment would give it a head start.

Pot 3 – Sheltered Spot in the Garden: This dahlia was placed in a sheltered spot in the garden, protected from the harshest winter conditions but still exposed to the natural elements.

Pot 4 – Dug Up: For this pot, I went traditional. I dug up the tubers and stored them indoors, away from the cold.

The Results

As you will see below, although all of the dahlias were ultimately fine, there was a clear winner and I have replicated the experiment with similar results since.

Pot 1 – Left in Place: The dahlia that had been left exposed showed signs of struggle. Sparse foliage and delayed budding indicated the toll the harsh winter had taken. However, with some extra care, it began to show signs of recovery.

Pot 2 – Brought Inside: This dahlia was the star of the experiment. Being initially indoors and then transitioning to a greenhouse seemed to work wonders. It was the first to sprout, with robust green shoots. As the weeks progressed, it flourished, producing vibrant blooms well ahead of the others.

Pot 3 – Sheltered Spot in the Garden: This dahlia also fared well. While it wasn’t as advanced as the greenhouse dahlia, it still showed healthy growth and was the second to bloom. The sheltered spot in the garden seemed to offer just the right balance of protection and natural exposure.

Pot 4 – Dug Up: The traditional method had its merits, but it also required the most effort. The tubers, once replanted, took some time to establish. By mid-spring, it was on par with the dahlia left in place, both showing similar growth patterns.

Rick Durham, extension professor, Department of Horticulture Says: Dig only your healthiest plants. Roots from any plant that may have shown signs of a virus should end up in the trash.

Conclusion

As perennial flowers, your Dahlias in pots can be stored indoors over winter to protect them from winter frost. And by following the tips we have detailed above you can ensure that the same plants can bloom in your garden the next year. Keeping your dahlias safe and healthy overwinter doesn’t require much effort and as long as you have the right location to keep the plants cool and dry over the winter months. It is also essential to make sure that you take the steps to start the dormancy process in the plant, cut back dying foliage, and dry out the plant sufficiently before you put the dahlias in place for overwintering.

Overwintering Dahlias in Pots Infographic
Overwintering Dahlias in Pots Infographic

Garden Doctor Tips

“If leaving dahlias outside, wrap pots in horticultural fleece to prevent them from freezing!”

“For Dahlia’s left in the ground, prune and lift in the autumn once the foliage has died back!”

“Bring Dahlia’s in before the first frost and then place them back outside after the last frost!”

“Cut Dahlia stems back to around 2-3 inches once the plant has begun to die back for the winter!”

Frequently Asked Questions

Can you leave dahlia tubers in the ground over winter?

Dahlia tubers will not survive winter in extremely cold climates if they are left in the ground. The tubers will rot if the soil is too wet, and they cannot tolerate heavy frost. It is a better idea to dig up the tubers that are in the ground, clean them off, and store them in a dry place until spring.

Do you cut dahlias back for the winter?

Yes, once the foliage has died back, cut the stem back to 2-3 inches. This will help to prevent rot and keep the tuber healthy over the winter.

When should I lift my dahlias for the winter?

You can lift your dahlias anytime between October and November once all of the foliage has died back. Make sure to wait until the first light frost, as this will help to ensure that the tubers are properly dormant.

How to lift dahlias for winter?

Carefully dig up your tubers, making sure to gently brush off any excess soil. Inspect the tubers for any signs of rot or damage and discard any damaged tubers. Store the healthy tubers in a cool, dry place until you’re ready to replant them next spring.


Author

Trevor Wright is not just a seasoned horticulturist; he’s the esteemed Garden Doctor. With a BSc in Horticulture and years of hands-on experience in the soil, Trevor has become a trusted mentor for all things gardening. As the founder of Garden Doctor, he’s committed to clarifying the intricacies of gardening, offering straightforward advice that’s rooted in years of practice. His writing is a garden of how-tos, savvy insights, and comprehensive guides that enable individuals to nurture and grow their garden dreams. When he’s not knee-deep in garden beds, Trevor is at his keyboard passing on his green-thumbed wisdom to budding gardeners, ensuring that the legacy of sustainable and joyful gardening blossoms far and wide.


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