Best expert advice on growing dahlias

Last Updated on April 16, 2024 by Suttons Horticultural Team

You can plant dahlia tubers or grow them from seed, but if you want to know how to grow dazzling dahlias, start with this collection of carefully curated content from the internet. Our comprehensive guide is filled with tips and tricks from those who know dahlias best – experienced garden bloggers and dahlia enthusiasts. Learn the basics from these experts and you’ll soon be growing award-winning dahlias in your own garden or allotment.

This article was originally published on 15 February 2021 and reviewed by the Suttons horticultural team and updated on 29 February 2024.

Contents

• Best advice on growing dahlias from tubers or seed
• Best advice on supporting dahlia plants
• Best advice on growing dahlias for cutting
• Best advice on combating dahlia pests and diseases
• Best dahlia varieties to grow
• Best advice on how to overwinter dahlia tubers

Best advice on growing dahlias from tubers or seed

In his excellent video guide to starting dahlia tubers, RHS judge Martin Fish of Pots & Trowels says that he wouldn’t usually plant out his tubers until mid-April, at the very earliest. But if you want flowers a bit sooner, Martin says you can pot them up towards the end of March and keep them in a frost-free greenhouse or conservatory until any danger of frost has gone. So why has Martin started potting up his dahlia tubers in February? If you want to learn how to take cuttings and get a few free plants, watch his full video for a demo.  

There’s not much Geoff Hoyle and his wife Heather from Stockport in Cheshire, aka Dahliaholic, don’t know about dahlias as their comprehensive dahlia video growing guide demonstrates. Filmed in their spectacular garden where they raise 150 dahlia varieties from tubers each year, they share their annual routine from March through to November as they turn their entire suburban plot into a dahlia paradise. Quite stunning!

It’s best to plant dahlias in rich soil in a sunny spot in the garden according to Carol, The Sunday Gardener, who says that while dahlias will need a bit of time and attention, the results are worth it. Some top advice in her dahlia growing guide is to pinch out the growing tips once the plants are established to get more side shoots and more blooms.

Most people cultivate dahlias from tubers, but some varieties can be grown successfully from seed, as Geoff, The Biking Gardener, confirms in his article: Amazing annuals: Dahlias. He recommends limiting your seed growing to dwarf varieties and those with single or semi-double blooms – great for bees and butterflies. His secret is to treat them as annuals and sow in April when the light is good and they’ll germinate quickly.

Best advice on supporting dahlia plants

Garden designer Jack Wallington, who grows beautiful dahlias organically and peat-free in his garden and allotment in south London, has some excellent tips on how to support your dahlia plants in borders, pots and for cutting. We can’t argue with his philosophy that “when life throws you lockdowns, you’ve got to pick some dahlias”.

Have you heard of the ‘cobweb method’ of staking dahlias? Over at @lookinsidemygarden, Sophie Valentine shares a short video of how to perfectly support the top heavy blooms as they grow. After last year’s success, Sophie says this is her go-to method as it’s “easy, affordable and it works SO well!” She simply pushes in the canes and then weaves the string into a giant cobweb pattern. Once the dahlias get tall enough, the web ‘disappears’.

Best advice on growing dahlias for cutting

Interior designer and gardener Rebecca at My English Country Cottage calls them “darling dahlias” for their beauty and variety, and they are one of her top choices for glorious indoor flower displays. She grows her own dahlias for cut flowers and advises you to only pick blooms that are in full flower as buds don’t usually develop once cut from the plant. 

Head of gardens at Balmoral Castle, Kirsty Wilson from @getplantinghort says that dahlias are one of her favourite flowers. But did you know that the striking architectural blooms are also edible? “Some people use the petals scattered over salad and to decorate a range of puddings,” she says. Follow her on Insta to pick up lots of fascinating plant knowledge.

Best advice on combating dahlia pests and diseases

“I’ve had a few dahlia flowers that had fasciation this year,” says Sophie from @floraldaysintheshires. “This is when the flowers are misshapen or elongated.” While this can be caused by environmental reasons, it’s also a sign of gall, a highly contagious bacterial disease that enters the plant through wounds. Sadly her dahlia is infected, and the tuber is also showing signs of rot. Watch her short video reel so you’ll know what to look out for, and be sure to burn any plants that succumb.

There’s no doubt slugs and snails adore fresh young dahlia shoots and leaves to chomp on. In his guide to getting a great show by growing garden dahlias, Alan from Down to Earth suggests using pellets to control them until your dahlia plants are well established. Earwigs are also partial to nighttime snacking on dahlia petals, but Alan says you can lure them away by popping wood wool into a little flowerpot and perching it on a cane amongst the plants.

Self-confessed dahlia addict Dan, aka The Frustrated Gardener, raises 60 dahlia varieties on his allotment and still wants more! He prefers a natural approach to dahlia pest control and was fortunate to have a frog colony under the shed to gobble up any threatening slugs and snails, as well as a battalion of ladybirds who devoured the invading black flies.

Best dahlia varieties to grow

Alexandra of The Middlesized Garden interviewed dahlia expert and award winning gardener Steven Edney to produce her inspiring and thorough guide to choosing and growing dahlias. When pondering the best dahlias to grow, Steven says to consider whether you want to attract pollinators or produce striking cut flowers. Bees and other insects find simpler single or semi-double dahlias much easier to access for pollen, but the dense and showy pom-pom, cactus or dinner plate varieties look fabulous in a vase. Or you could simply select the dahlias you love the look of.

Ria from @snippingstems says she’s totally in love with Dahlia ‘Labyrinth’. Although it took a little while to get going, she said it went on to survive a mini heatwave and then took a battering from the wind and rain. Despite all this, the gorgeous two-toned blooms are still going strong at the end of September. Follow her on Insta for lots more advice including a helpful reel on dahlia lessons she’s learned along the way.

Many people’s favourite dahlia, ‘Café au Lait’ gets a vote from Naomi Slade, gardening journalist and author of Dahlias, beautiful varieties for home and garden (Pavilion, 2018). Sharing a gorgeous photo of a late September bloom, she describes this dahlia variety as “laggardly but charming, soft, ruffled.”

The 3 Growbags – sisters Laura, Elaine and Caroline – have strong and differing views about the kind of dahlias they appreciate, as they reveal in their honest and entertaining blog post Dahlias: too dire to dare? While Laura eschews elaborate and showy dahlia blooms to opt for quieter and more subtle single varieties, Elaine’s dahlia growing attempts were thwarted by pests. Caroline, meanwhile, is a huge dahlia fan and the more brilliant and daring the better: “In December I get out the Christmas lights and in May I get out the dahlias.”

Best advice on how to overwinter dahlia tubers

Over at popular YouTube Channel, In the Garden with Eli and Kate, Eli explains that there’s no one-size-fits-all answer to whether you should lift your dahlia tubers or leave them in the ground over winter. Where they live in Scotland, it’s better to lift the tubers as the wet winters cause them to rot. She stores her tubers in the shed, individually wrapped in newspaper so any rot or disease can’t spread and infect the others. 

In her beautifully filmed and presented video on potting up dahlia tubers, Katrina of Homegrown Garden explains how she lifts her dahlia tubers at the end of the flowering season and puts them in pots of spent compost to sleep over the winter in her basement. Her straightforward step-by-step guide shows you how to get them established again when they wake up in spring, and the results can be seen in a lovely photo of Katrina surrounded by pastel blooms in her dahlia border.

Do you usually dig up your dahlias at the end of the growing season? Alexandra from The Middlesized Garden YouTube channel says it’s OK to leave dahlia tubers in the ground over winter. She cuts back the old foliage and stems, then protects the plant by covering it well with a big mound of compost or mulch.

Meanwhile, Amy from @chicksandveg warns that dahlias are not hardy at all. “If they get caught by frost, their tubers will rot,” she adds. Having said that, she’s not only leaving her dahlias in the ground from now on, but she’s taking a short cut on the mulching as well! “Rather than adding an expensive or time consuming mulch I’m adding freshly raked leaves to this area,” she says. Amy did the same last year and has the best display yet. See her images for proof! 

Follow the wise words of the experts and you’ll have a stunning display of dazzling dahlias this summer – in the border, the allotment or even in a container on the patio. And if you’re a bit late to start from tubers or seeds, choosing a potted dahlia plant  will give you the quick results you’re after. Who could possibly resist?

Lead image: Dahlia ‘Dinnerplate Collection’ from Suttons/©T&M

See expert contributors here

• Martin Fish, professional gardener, RHS judge, writer, columnist, broadcaster.
• Geoff Hoyle, Dahlia-specific gardening content creator.
• Carol Bartlett, Gardening blogger and content creator.
• Geoff Stebbings, Kew Gardens trained gardener, author, journalist and blogger.
• Jack Wallington, RHS qualified landscape designer.
• Sophie Valentine, Self-taught gardener, content creator, gardening course leader, YouTuber.
• Rebecca Lovatt, Interiors content creator, Preloved magazine columnist.
• Kirsty Wilson, BSc Honours, Horticulture with Plantmanship, head of gardens at Balmoral Castle, garden designer, author.
• Sophie van Gerwen, Gardening course leader, content creator.
• Alan Down, Garden writer, blogger, radio & TV, consultant. President of the Horticultural Trades Association.
• Dan Cooper, Landscape Management degree, exhibitor in National Gardens Scheme.
• Alexandra Campbell, Garden writer, journalist, content creator.
• Ria, Gardening content creator.
• Naomi Slade, Journalist, author, designer and consultant. Winner of GMG’s Practical Journalist of the Year 2022.
• The 3 Grow Bags, Gardening bloggers, YouTubers and authors.
• Eli and Kate, Gardening content creators, YouTubers, bloggers.
• Katrina Harrison, Gardener, YouTube content creator, and blogger.
• Amy, Home gardener, content creator.