How to plant, grow and care for dahlia flowers

How to plant, grow and care for dahlia flowers

Although native to Mexico, dahlias have become a British classic. However, a few years ago, they lost popularity with gardeners who thought they were an old-fashioned, showy, time-consuming plant that their great-grandfathers grew on their allotments.

Fortunately, after decades of stagnation, they are enjoying a resurgence due to their wide range of colors and impressive flower power – the single flowers are also a magnet for bees and butterflies. This is what made them a popular and crowd-pleasing plant.

We visited Sarah Raven's cutting garden in East Sussex where she grows a stunning collection of dahlias.

“I really like dahlias because you get them in almost any color,” she says. “They come in an amazing array of shapes and, most important of all, they make good, very long-lasting cut flowers. They are incredibly bright and generous.

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There are many different types of dahlias from pom pom varieties to cactus varieties

They are easy to grow. Today you'll find dahlias grown in patio pots and with a modern whimsical style and colorful borders, they are a must-have for your patchwork. Flowers in soft shades are often the best choice, as they not only provide a handful of fresh cut flowers to fill your vases every day throughout the summer but they make gorgeous bouquets, so they have become a favorite for brides.

Types of dahlias for cultivation

You'll find dahlias come in a variety of shapes and sizes, from tiny pompons and those that resemble other familiar flowers like waterlilies, peonies and chrysanthemums to cacti with spiky petals, and attractive giants like 'Bilbao' and 'Manhattan'. Island', whose flowers are the size of a dinner plate, plus many others.

They come in almost every shade and color combination, with the exception of the elusive blue and also with foliage from dark green to dark bronze.

Sarah Raven recommends Waltzing Matilda which she says is great for pots and border edges. Since it is a single flower, it is also ideal for pollinators.

She also recommends the Molly Raven, named after her daughter, and which reminds her of Venetian marbled paper.

For a real show, Sarah recommends the bright pink Emory Ball, which produces giant blooms. “You just need one in a pot and have a flower arrangement. They're just gorgeous,” Sarah says.

Crocus Dahlia “Cafe au Lait”

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Credit: Saffron

GH garden writer Patty Barron recommends Cafe au Lait. “They have huge, bulbous flowers with masses of ruffled petals in shades of light coffee cream, with undertones of iced peach!”

Crocus Dahlia “David Howard”

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“This ornamental dahlia has beautiful orange and ocher flowers that contrast with the chocolate-colored foliage,” says Ben Kendrick, director of homes and style at Country Living.

Crocus Dahlia “Thomas A. Edison”

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“I've grown dahlias on a plot and in the garden, and Thomas Edison is my favourite,” says Simon Swift, executive editor (digital) at GH. It continues to produce huge, deep purple flowers.

Sarah Raven Dahlia “Roxy”

“The simple, open flowers in showy pink make the open-air Roxy a must-have for pots,” says Patti. “It's definitely the tallest dahlia you could hope for.”

Tangerine Dream Dahlia Collection
Crocos Tangerine Dream Dahlia Collection

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This collection of complimentary flowers includes Totally Tangerine, Pink and Orange Anemone Dahlia, French Can, and Zundert Mystery Fox.

Thompson and Morgan Dahlia “Cornell Duet”

If you're a fan of dahlias with a sculptural look, this set includes Cornel and Cornelian Bronze – apricot and red blooms.

When to plant dahlias

Although they can be grown from seed, all dwarf bedding species are generally grown from tubers, making them one of the easiest plants to grow of all – when the danger of frost has passed, simply dig a hole and plant them in. the earth.

Dahlia (Georgina) tuber on garden soil before planting

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Dahlia plants are best grown from tubers

To grow best, you will need to find your dahlias in a sunny location. But the key to success lies in the soil. Dahlias require good drainage and are heavy feeders, so enriching the soil before planting with garden compost or well-rotted manure will pay dividends, as will “feeding” the plants throughout the growing season.

How to grow dahlias

Dahlias use large amounts of potash to develop roots and potassium to produce flowers, so look for a fertilizer that is rich in these nutrients and contains only small amounts of nitrogen to maintain healthy growth.

It is also important to keep your dahlia beds free of weeds because they will compete for water, nutrients and light and often harbor pests and diseases. Mulch is effective in controlling weeds, and will also keep the soil cool and retain moisture, which is important because dahlias are very thirsty plants.

Taller varieties also need staking because their hollow stems often break under the weight of their large flowers. Place sturdy stakes at planting time and use soft string to tie the stems loosely to avoid pinching the developing plant. When the plant is about 20cm tall, it will form a final flower bud.

How to grow dahlias

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Dahlias should be staked to avoid falling over

Squeezing the tips as they grow will encourage branching and more flowers, so if you want a bushy plant with clumps of flowers, rather than one big beautiful flower, remove this bud and any small buds next to it. Remove all fully spent flowers along with the stem regularly to maintain the plant's productivity otherwise it will go to seed.

How to protect dahlias

Because dahlias are delicious meals for caterpillars, which chew holes in their leaves during the day, and their succulent leaves and gorgeous flowers are a favorite midnight snack for slugs and earwigs, you'll need to set traps to protect the plants. Slugs thrive anywhere moisture may be retained, so common places to find slugs will be under pots and containers, under mulch, under boards, under rocks, and deep in overgrown plants.

Caterpillar on a flower

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Protect dahlia plants from pests such as caterpillars

Surrounding the plant with crushed eggshells or a loop of copper wire may keep slugs and snails away, or you can use their natural enemy, nematodes, available at garden centers. They just need to be mixed with water and applied to the ground through a watering can. Although they will not destroy larger surface-dwelling slugs, nematodes will kill small, small soil slugs.

Earwigs can also be easily controlled by taping tall bamboo canes all over your patch, with an upside-down bowl on each, stuffed with damp straw, grass or hay. Earwigs like to hide during the day, so they're easy to catch. In the morning, empty the container and dispose of it.

How to cut dahlias

To use dahlias as cut flowers, cut the flowers when they are fully open. Condition the flowers immediately after cutting by immediately immersing the cut ends in warm water, then when you are ready to arrange them in the vase, cut off about 1mm from the base of the stem and place the stems in warm water. Doing this while changing the water every 2-3 days will increase the life of the flowers in the vase.

Dahlia tubers overwinter

Dahlias, which bloom around late July, will end their lives when frost blackens the foliage. The plants can then be cut to about 15 cm, dug up and stored in a cool, frost-free place for the winter.

Freshly picked dahlia flowers at our organic flower farm are ready for market

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Dahlia tubers can be left in the ground over the winter if they are protected

Treat the tubers carefully before storing them. Allow the hollow stems to drain by placing them upside down in a tray and after a few weeks, remove the dry soil adhering to the tuber with a soft brush and sprinkle with yellow sulfur to discourage mold and fungi, then place the tubers upright in a storage box and cover with peat or slightly damp sand.

It's a good idea to inspect your dahlia tubers regularly throughout the winter to look for signs of mildew or rot. Cut out any affected areas with a clean, sharp knife and then sprinkle with sulfur.

Dormant tubers can be revived in spring by planting them in containers and any shoots can be used for cuttings, which are grown in individual pots and planted in May and June. Dry tubers can be planted where you want them to flower in late April.

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