How to grow dahlias in pots so they absolutely thrive all autumn

These bold blooms will flower all summer long – even in containers

Dahlia flowers growing in pots and window boxes on a balcony
(Image credit: Getty Images)

Fancy filling your garden with flamboyant and flouncy flowers? Then you need to learn how to grow dahlias in pots, stat!

Famed for their dramatic beauty, dahlias usually wind up on every gardener's list of must-try garden ideas at least once (at least), and for good reason: they bloom straight through summer and well into the autumn.

And this means, yes, that they're the perfect flower to work into your container garden ideas, adding a much-needed pop of colour in the duller months of September and October. 

How to grow dahlias in pots

Worried you don't have enough room in your garden borders for dahlias? Don't be: they can absolutely flourish in containers, provided the pots are large enough.

‘Dahlias are perfect for most gardens and homes due to their versatile nature,’ promises Dani Turner, customer experience director at family-run florist Bunches

Still, while there are many different dahlia varieties to choose from, Dani suggests you look for one 'that is slightly smaller and compact' if you're sussing out how to grow dahlias in pots, as 'some can grow as tall as 5ft'.

Dahlia in container

(Image credit: Getty)

Keen to get started? We spoke to the experts (and drew upon our own experience with garden trends) to figure out everything you need to start growing dahlias in pots and containers.

You're welcome!

What you’ll need

Before you start reading up on how to grow dahlias in pots, it's a good idea to gather all of the equipment you will need first.

Step by step guide:

Once you've sourced all of the equipment you need, you can get to work planting your dahlias up in pots.

Here's what you need to do.

1. Choose the right container

‘For Dahlias that are going to be grown in a pot, it is best to choose one that is at least 30cm in diameter and 40cm deep,’ Dani recommends.

Gardening expert Fiona Jenkins at Myjobquote.co.uk echoes this sentiment. ‘For most dahlia varieties, you want to choose a fairly large pot; a 12 – 14 inch (30 - 35cm) diameter pot is ideal and 12 inches of depth is perfect.’

Because they, ‘put on a lot of top growth, a fairly heavy pot is required to counter-balance all the top foliage, otherwise they will blow over,’ says Angela Slater, Gardening Expert at Hayes Garden World

She recommends a heavy terracotta or glazed clay pot. You may also need to stake your dahlias as they grow, to prevent them from falling over.

Dahlia in container

(Image credit: Getty)

2. Wait for the right time

Dahlia tubers can be started into growth in March or April in pots undercover, as this will give them the optimal conditions to develop and grow, compared to when a sudden frost could hinder their growth or potentially kill the plant entirely.

‘To plant, mound a few inches of potting soil at the bottom of the pot while forming a little bit of a hill. Balance the tuber on the mound and then carefully fill in around the tuber with your potting soil,’ Fiona instructs. 

'Press and firm it around the tuber gently as you go along.’

You can plant them out in the garden in late May and June. 

3. Find them a sunny spot

‘Dahlias are sun-loving plants that require at least 6-8 hours of direct sunlight each day to thrive,’ suggests Jason.

‘Place your pots in a sunny spot on your patio, balcony, or in your garden. Ensuring that they receive adequate sunlight will encourage strong growth and abundant blooms.’

In particularly scorching summer weather, you can move your potted dahlias into the shade to give them some respite but they do prefer sunny conditions.

Dahlia in container

(Image credit: Getty)

4. Add manure

Dahlias are not fussy, and will grow in any fertile, moist, but well-drained soil. 

'To enrich the soil and help them grow, you can add organic matter, such as manure, to give the soil more nutrients,’ suggests Dani.

5. Fertilise regularly

Dahlias are ‘greedy feeders,’ according to Angela, so they ‘need a constant supply of nutrients.’

Once your dahlia plants begin to flower, you need to regularly provide them with fertiliser to help them maintain a healthy foliage throughout the growing season. ‘Use a balanced, water-soluble fertiliser that is suitable for flowering plants,’ affirms Jason.

‘Dead-heading or picking the blooms is essential to keep the plant flowering as long as possible,’ proffers Angela.

Dahlia in container

(Image credit: Getty)

5. Water wisely

As you may expect, you will need to water your dahlias for them to thrive. ‘While they do require consistent moisture, it's important to avoid overwatering, as this can lead to tuber rot,’ reveals Jason.

‘Check the soil moisture regularly by inserting your finger into the potting mix. Water the plants when the top inch of soil feels dry to the touch.’

You’ll also want to ensure that the pot or container that you’ve chosen has good drainage to prevent the soil from becoming waterlogged, which can also be detrimental to the plants.

Dahlia in container

(Image credit: Getty)

6. Watch out for pests

Aphids can be a problem for dahlias, but, ‘they can be controlled by rubbing off between finger and thumb or by feeding the birds who will dispose of them for you,’ says Angela.

‘Earwigs can also be a problem but can be controlled by placing an upturned pot stuffed with straw on top of a cane.’ Keep an eye on your beautiful blooms so that you can immediately see if you have any pest problems and deal with them before too much damage is done.

7. And don't forget to deadhead

We've said it before and we'll say it again: if you're going to learn how to grow dahlias in pots, you also need to learn how to deadhead dahlias so they flower beautifully all autumn long.

'Keep it trimmed down, and keep removing the wilted flowers, and you will have a neat bushy plant,' says Christopher O'Donoghue, one of the co-directors at Gardens Revived.

Sounds easy enough, right? Next up: learning how to grow peonies in pots (if you fancy something a little more advanced, that is!).

FAQs

What are the best dahlias for growing in pots?

You’ll want to choose a variety of dahlia that is suitable for container gardening. 

As ‘some dahlia plants can grow quite large, it's best to opt for dwarf or compact varieties,’ says award-winning garden designer Jason Williams, also known as The Cloud Gardener

‘These smaller plants are well-suited to container growth, maintaining a more manageable size while still producing an abundance of beautiful blooms.’


What should I do with my potted dahlia in the winter months?

The added benefit of growing your dahlias in a pot or container is the fact that you can easily move them, either if or when you move home or during the less hospitable colder months.

Dani reveals, ‘although dahlias are usually bought annually, they can be kept alive during the winter months.’

‘To do this, after the first frost has killed the foliage, bring the potted dahlias inside to a cool, dry and darkened place – a basement or a garage would be perfect for this.’

‘They don’t need much water during the winter but just keep checking on them to make sure they aren’t too wet or are in need of some water to rehydrate them,’ she concludes.

Ellis Cochrane
Contributor

Ellis Cochrane has been a Freelance Contributor for Ideal Home since 2023. She graduated with a Joint Honours degree in Politics and English from the University of Strathclyde and between her exams and graduation, started a lifestyle blog where she would share what she was buying, reading and doing. In doing so, she created opportunities to work with some of her dream brands and discovered the possibility of freelance writing, after always dreaming of writing for magazines when she was growing up.


Since then, she has contributed to a variety of online and print publications, covering everything from celebrity news and beauty reviews to her real passion; homes and interiors. She started writing about all things homes, gardens and interiors after joining Decor & Design Scotland as a Freelance Journalist and Social Media Account Manager in 2021. She then started freelancing at House Beautiful, Country Living and in Stylist’s Home team. Ellis is currently saving to buy her first home in Glasgow with far too many Pinterest boards dedicated to her many design ideas and inspirations.

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