Dahlias come in a range of colours and shapes
Image: Dahlia ‘Tropical Sheer Heaven’ from Thompson & Morgan (©Visions BV, Netherlands)

Here’s a masterclass on growing dahlias courtesy of some of our favourite gardening bloggers, YouTubers, and Instagrammers. When it comes to dahlias, not only do these growers know their stuff, but they’re also happy to share their knowledge and experience. Whether you want to plant dahlia tubers or raise them from seed, this is the place to start. 

This article was reviewed by T&M’s horticultural team and updated on 4th April 2024.

Learn about the origins of dahlias to get the best from them

Dahlias are related to daisies and sunflowers
Image: North Leeds Garden Design

A flower with countless variations, dahlias take their name from the Swedish botanist Anders Dahl who lived in the mid 1700s, says pro gardener Annabel Bridge at North Leeds Garden Design. Originally a native of Mexico, Annabel explains that dahlias are, “closely related to the daisy and the sunflower,” with blooms made up of “numerous delicate petals surrounding a central core.” Read Annabel’s full article about the wondrous world of dahlias to find out why so many people develop an obsession with these special flowers.

Expand your dahlia collection to include unusual varieties

Waterlilly dahlias have a full double blooms
Image: Gardening Step by Step

There are currently 15 recognised groups of dahlias ranging from the single flowered varieties (group 1) through to the stellars (group 15). Offering a full illustrated explanation of the properties of each group, BBC Gardener of The Year finalist, Martin Cole from Gardening Step-by-Step explains each of the different types of dahlias along with suggestions for some of the most special cultivars to try.

Throw in some bold colours

Dahlia ‘Black Jack’ is a sumptuous shade of blackcurrant 
Image: @beverleys_garden_no37

Beverley finds that dahlia ‘Black Jack’ is just the thing to complement the pastel colours of her garden. “The deep crimson, purple & pink tones in this dahlia really set off the pastel shades I’m more used to growing,” she says. She recommends taking a risk and trying out a new colour or variety. Like Beverley, you might find that a dark and moody dahlia might be just the thing to bring your whole scheme to life! Follow this flower gardening over at @beverleys_garden_no37.

Choose compact bedding dahlia varieties to fill patio containers

Bedding dahlias stay compact with delightful blooms
Image: Dahlia ‘Figaro Mixed’ from Thompson & Morgan

If you’re intending to grow dahlias in small pots, do make sure you select bedding dahlias, says John Moore over at Pyracantha. That’s because some varieties of dahlias grow very tall. That said, John agrees that you can grow bigger dahlias on your patio provided you choose a big enough container and stake them when planting. His top tip – if you’re planting in pots, make sure you water: “They prefer to be soaked down occasionally, rather than watered little but daily.”

Stimulate healthy root growth under cover before planting out

Damp compost prompts your tubers to wake up in spring
Image: @rudge_yorkshire_gardener

To get his favourite dahlia tubers rooting in early March, Rudge pots them up into damp compost in the safety of the garage. He only moves them out into the greenhouse when all risk of frost has passed. “It is the UK so anything could happen!”, he warns on his Instagram @rudge_yorkshire_gardener. However, it pays not to be too impatient, he warns. Dahlias are always worth the wait! Check out his grid for inspiration.

Keep dahlias protected from frost until mid-May

Use one litre pots to plant your dahlia tubers in spring
Image: @nicoleatcherrygarden

Even when April arrives, it pays to be cautious and pot up your dahlia tubers under cover instead of rushing to get them into the ground, says Nicole Laird over at @nicoleatcherrygarden. Late frost can blacken leaves and set you back, she says. “Having them in pots, tucked away in my greenhouse or cold frames gives me a chance to protect them a little better if temps are going to get low,” says Nicole. Alternatively, plant them straight into the garden after your last frost date, which for Nicole is mid-May.

Set up an irrigation system to water your dahlias

An irrigation system saves water and time
Image: CottoVerdi – with Annette on YouTube

Because dahlias require quite heavy watering, you might wish to take a leaf from the book of YouTuber Annette over at CottoVerdi. Do check out her video showing how to prepare a dahlia bed complete with an irrigation system. She says, not only does this save a lot of bother, it’s also a great way to avoid wasting water as you’re watering the roots directly and not wetting the petals and leaves which can turn rotten and soggy. Want some more tips from this experienced grower? Take a look at her video guide to potting up dahlias for a thorough explanation.

Construct a support frame for superb cut flowers

A raised bed and support system helps support your growing dahlias
Image: My Home Farm

One great way to grow dahlias is to build a special raised bed and support system. That’s just what Mars and Kirsten from @my.home.farm.uk have done. Not only does it provide a protected growing space for your dahlias, but the overhead support system negates the need for bamboo stakes which can blow over. This looks neater and makes it easier to cut dahlias for your indoor displays. Head over to Mars and Kirsten’s Insta to watch Mars build the raised bed and special supports.

Create natural looking supports from sticks and twigs

Provide support for large flowered dahlias like the enormous ‘Penhill Watermelon’
Image: @Iamagardener

After a more natural look in your beds and borders? Take a leaf out of Laura’s book and use twigs and sticks to support your border dahlias. This resourceful Instagrammer collects cut sticks from a clearing nearby and cleverly weaves them through her dahlia bed to support the growing plants. She’s definitely doing something right! Check out her photo of a dahlia ‘Penhill Watermelon’ blooming with astounding proportions on her flower-filled Instagram grid at @Iamagardener.

Deter slugs and snails with organic slug pellets

The small holes in this dahlia flower indicate a snail attack
Image: The Middle-sized Garden

Slugs and snails are the number one dahlia pest, says Alexandra at The Middle-sized Garden. Having turned to a professional organic gardener for advice, she says managing these slimy pests is possible without using harsh chemicals. She advocates a two system approach – sparing use of organic slug pellets made from ferric phosphate which stop slugs in their tracks but without harming garden birds and animals, or simply picking the pests off by hand. She says, “However, if there are enough flowers, a few nibbled leaves and petals won’t really show.”

Your tubers are ready to lift when frost blackens the foliage

Clean and dry your lifted dahlia tubers to prevent rot setting in
Image: @livingthegardendream

Dahlias are tender perennials and so shouldn’t stay in the ground during the winter for the frost to get them. Instagrammer, Tessa from @livingthegardendream offers some great and simple advice for overwintering dahlias: “When the frosts blacken the foliage you cut it back and gently lift them, turn them upside down to dry, clean them up and store them somewhere dry and frost free over winter.”

Leave tubers in the ground over winter in mild areas

Dahlias flower in late summer and early autumn
Image: Marie Shallcross, Plews Garden Design

If you live somewhere where winters tend to be mild (like the South West of the UK) you may not need to dig up your dahlia tubers at all. Marie from Plews Garden Design offers the following advice on her Insta feed @plewsgd: “In well drained soils in mild areas, dahlias stand a good chance of overwintering in the ground. So you need do nothing.” In this case, applying a thick mulch should be enough to prevent heavy frosts from damaging them.

Growing dahlias is one way to guarantee a brighter, bigger, bolder flower display in your garden this season, and because they make such wonderful cut flowers, it’s also a great way to bring the beauty of the outdoors into your home. We hope you’ve enjoyed our pick of the best online advice on growing dahlias – now all you need to do is decide which cultivars to grow this spring.

Choose from our full range of dahlia tubers – or, if you’re looking for dedicated growing advice and expert gardening tips, head over to our dahlia hub. You can find lots more information about keeping your garden looking beautiful this summer on our summer flowers hub page.

Sophie Essex

Sophie Essex is a freelance garden writer with a passion for horticulture and environmental conservation. With a BSc in Botany/Plant Biology from the University of Plymouth, she further honed her expertise through a Masters of Science in Biodiversity and Taxonomy of Plants from The University of Edinburgh.

Sophie has also worked as a professional gardener and landscaper, showcasing her practical skills by transforming outdoor spaces. Her commitment to fieldwork is further evident in her acquisition of a Certificate in Field Botany from the Royal Botanic Garden Edinburgh, and over the years, she has interned at the Eden Project, Cornwall, the National Trust for Scotland and the Royal Botanic Garden Edinburgh. Find more information about Sophie over at LinkedIn.