Dahlias: how to grow beautiful dahlia flowers

Clare Foster explains how to grow dahlias, how to care for them, whether they are perennials, and chooses favourite varieties
Orange-red ‘Karma Fiesta’Eva Nemeth

How to care for dahlias

Always stake your dahlias as soon as you plant them out and then tie them in as they grow. When the plants are fully established, they will hide any unsightly sticks and won't slump over. Use strong pieces of wood, not bamboo, which is the perfect hiding place for earwigs who will snack on your tender plants. Always protect against slugs - this is particularly important in the early stages to avoid heartbreak.

As soon as you see buds developing, start feeding your dahlias. The folks at the National Dahlia Collection recommend a proprietary tomato food once every 10 days.

When your plants start blooming, be meticulous about deadheading. If you keep on picking the flowers, you'll have a constant supply of blooms from July to November. Before you put them in a vase, Sarah Raven recommends re-cutting the hollow stem under water to avoid airlocks.

A dahlia arrangement by Rachel Siegfried

Eva Nemeth

What varieties of dahlia are best?

The reason that there are so many shapes, sizes and colours of dahlia is because they have more chromosomes than other plants. This means there is more variation in form when the plants cross-fertilise, resulting in the incredible diversity we see today. There are more than 10 categories of dahlia, grouped by flower shape, including pompon and ball dahlias, decorative, waterlily, peony, cactus, single and anemone.

The anemone type 'Totally Tangerine’ is palest apricot with a contrasting darker centre

Eva Nemeth

‘When you’re growing dahlias as cut flowers, it’s best to go for small to medium flowers, with the odd larger one thrown in,’ says Rachel Siegfried. ‘The other crucial thing is height: you don’t want the dwarf, bedding-type dahlias because you can’t get the stem length you will need for cutting, so don’t go for a plant that’s going to be under a metre tall.’ Most dahlias can be used for cutting, but some are better than others – either because they last longer in the vase, or because they have tall and clearly defined stems. ‘If I had to choose just one type, it would be the waterlily dahlia because of the softness of it and because it just lends itself to cutting,’ says Rachel. ‘Singles, collarettes, anemones and cactus types don’t have quite as much vase life, but I still like to grow them for the variety of form.’

Rachel's particular favourites include the following;

Dahlia ‘Carolina Wagemans’ has two-tone, waterlily-type flowers

Eva Nemeth

Creamy white ‘Eveline’ has touches of soft lilac.

Eva Nemeth
  • Waterlily ‘Carolina Wagemans’: ‘When it first opens, its flowers are apricot, with a two-tone effect and, as it ages, it becomes more pink. It has good stem length and is prolific in flower.’
  • Waterlily ‘Sam Hopkins’: ‘This is the best of several dark waterlily types, with flowers of the deepest, velvety red – almost black in the centre.’
  • Decorative ‘Eveline’: ‘This has white flowers with a hint of lilac in the middle and around the edges of the petals. It’s one of my top bridal flowers.’

Lipstick pink cactus dahlia ‘Orfeo’

Eva Nemeth

The decorative ‘Peaches’

Eva Nemeth

The opulent flower of ‘Café au Lait’

Eva Nemeth
  • Cactus ‘Orfeo’: ‘This is an unbelievable colour – electric pink and almost iridescent – with large flowers. It’s a prolific flowerer and has good stem length.’
  • Decorative ‘Peaches’: ‘This is a decorative, with bicoloured blooms of warm peachy-orange with white tips to the petal.’
  • Large decorative ‘Cafe au Lait’: ‘I love its creamy, beige-pink flowers and wouldn’t be without it for its opulence and size.’

Dark-flowered cultivars are always popular, and recent introductions include D. 'Karma Choe', a water-lily type with dark velvety flowers suffused with crimson. D. 'Dark Desire' has ele­gant single flowers in deep chocolatey red with contrasting golden stamens. For something with more punch, D.'Acapulco' is a new cactus dahlia that has strawberry-red flowers with a deep pink centre, while D. 'Lorona Dawn' has distinctive, pink single flowers with a white ruffle and bright yellow centre. Another one-off is D. 'Alloway Candy', a double orchid type in pale pink tinged yellow. Also look out for D. 'Dakota', launched in 2011, with single flowers in pale orange, edged with red. This is just a handful of some of the new range available, with new varieties to look out for and try each year.

Dahlia 'Alloway Candy', a double orchid type with delicate, pale pink drooping petals, is rarely seen in the UK.Sabina Ruber

A short history of dahlias

Explosive shapes and fabulous colours make the dahlia one of the most visually arresting plants we grow, so it is surprising to find that it doesn't have the breadth of artistic history that many other plants have. This is partly because it is a relative newcomer to our gardens, arriving via Spain from Mexico at the end of the eighteenth century (although it had been widely cultivated in Mexico for hundreds of years before this). The first known illustration of the dahlia appeared in an Aztec herbal in 1552 - a simple coloured painting of Dahlia coccinea with its single red flowers - and it was around this time that the dahlia was first discovered by a European, Francisco Hernandez, physician to the King of Spain, who also illustrated several double-flowered dahlias in his own posthumously published herbal. Despite this initial flurry of interest, somehow the dahlia missed the boat - unlike other South American plants discovered by the Spanish at the same time, such as the passion flower and the tomato - and it wasn't until a good 250 years later that the plant was grown successfully in Europe.

The first dahlia species flowered in the Royal Botanic Gardens of Madrid around 1790, causing an immediate stir among the botanical fraternity of Europe. A frenzy of correspondence ensued, and the first dahlia seed was sent to Kew in 1798, but frustratingly the plants raised from this seed were promptly lost without being propagated, so the race was still on. The dahlia's introduction to Britain is widely credited to Lady Holland, a well­ known society figure and political hostess who sent back seed of Dahlia pinnata from the Royal Botanic Gardens in Madrid, and the first plants flowered in her garden at Holland House in 1804. But a colour painting of D. coccinea, which appeared in the same year in Curtis's Botanical Magazine, indi­cates that Lady Holland had been pipped to the post. The year before, in 1803, a few precious specimens of D. coccinea had flowered in the garden of John Fraser, a little-known plant hunter who ran a nursery in Sloane Square. Interest in this new, exotic plant accelerated quickly, to the point that it was described by the garden designer John Claudius Loudon in 1822 as 'the most fashionable flower in the country'. With seed of new, double varieties being thrown into the melting pot, horticulturists realised how wonderfully variable the dahlia was and soon an exciting range of different types was being developed, all of which were illustrated and pored over in botanical magazines. One of the most beautiful dahlia paintings is Pierre-Joseph Redoute's Dahlia pinnata (c. 1830), which captures the opulence and texture of the flower. But the tastefulness of this elegant painting is at odds with the subsequent development of the plant. Spurred on by an increased interest in growing dahlias for showing, breeders in the late nineteenth and early twentieth centuries got thoroughly carried away, producing increasingly outlandish varieties with monstrous flowers in colours that would look at home on a Fifties housecoat. This was the point at which, finally, the tables turned, and while the enthusiasm for competitive dahlia growing has always continued, the popularity of the dahlia in the garden went swiftly downhill.

Pale pink Dahlia ‘Sweet Love’

Eva Nemeth

The dahlia today

In the last decade, the dahlia has shaken off its tarnished reputation, thanks in part to the indomitable Christopher Lloyd, who boldly replanted the rose garden at Great Dixter with a colourful mix of dahlias, cannas and other exotics. 'Dahlias spell excitement,' he wrote, 'and we can all do with some of that in our lives.' Dahlias are arranged into several groups according to their flower shape, from the small, neat pompons to the explosive cactus varieties, and there are hun­dreds of varieties to choose from. You only have to look at the website of the National Dahlia Col­lection to see how many there are.

Where to buy dahlias

The National Dahlia Collection sell their astonishing collection of rooted cuttings by mail order until the end of March. They grow over 1,600 varieties in their 2-acre garden in Penzance which is open to the public from mid-July to the end of September.

Sarah Raven is a figurehead for the dahlia's triumphant return to fashion. She grows a huge number of dahlias in her garden at Perch Hill and sells tubers via her website.

de Jager was established in Holland in 1868 as flower bulb specialist. It maintains its reputation for producing the highest quality bulbs and in 2012 was granted a Royal Warrant as supplier of garden flower bulbs to The Prince of Wales. It sells an excellent range of dahlia tubers, including dinner plate dahlias for show.