Dahlias If you're looking for colour from mid-summer until the first frosts of autumn, dahlias are hard to beat. After years in the doldrums, these colourful beauties are back in fashion, with the dark-leaved 'Bishop of Llandaff' leading the way.

In this article

Recommended varieties Growing tips

Problem solver Where to see them

There are more than 50,000 different dahlias available in every shade imaginable, except the elusive blue. The plants come in a wide range of shapes and sizes, from the tiny liliput types that reach only 60cm (2ft) tall, to the enormous exhibition varieties with blooms the size of dinner plates.

Dahlias, originally from Mexico, were introduced into Europe about 200 years ago. The first plants were grown at the botanic gardens of Madrid and cared for by Swedish assistant curator Andreas Dahl, after whom they're named.

Dahlias are too tender to survive outdoors all year round in most parts of the UK. But the good news for gardeners is that they're easy to grow, thriving in any reasonable soil so long as they're kept moist.

Dark-coloured leaves
Dahlia 'Bishop of Llandaff': perhaps the trendiest dahlia of them all. Well-loved for its scarlet flowers, which are set off by the smokey-coloured foliage.
D. 'David Howard': pale orange flowers that are slightly darker in the centre.
D. 'Moonfire': this beautiful single-flowered variety has pale yellow blooms that are blushed with red at the centre.

Unusual flowers
D. 'Clair de Lune': this pretty variety is a collerette type, which means it has a ruff of small petals in the centre. The petals are a lovely shade of lemon yellow.
D. 'Clara May': this is a cactus-flowered type, but the ends of its petals are fimbriated. This means the petal ends are slightly split, giving rise to a spiky dahlia that resembles the spines of a hedgehog. Its blooms are made up of a range of pink colours with a yellow base to each of the petals. Its foliage is also attractive. Instead of the leaves having rounded margins, they almost have a cut-leaf appearance.

Easy ones for exhibition
D. 'Jomanda': the long, straight stems of this variety make it perfect for exhibiting. The ball-shaped flowers are a beautiful, autumnal, burnt orange colour.
D. 'Marlene Joy': the spiky flowers of this variety have white petals with pink tips.
D. 'Moor Place': the dark colour of this handsome pompom variety make it a favourite with exhibitors, as it hides a multitude of sins.

Dahlias are usually bought from garden centres or specialist nurseries as dry tubers in early spring. You can either plant these in the garden or start them off in pots of compost, to get shoots that can be used as cuttings. Alternatively, many types can be raised from seed, with plants becoming increasingly widely available.

When planting the tubers in the garden, wait until the soil is beginning to warm up in March or April. Dig lots of compost or well-rotted manure into the soil first, then bury the tubers about 15cm (6in) deep, with the old stems pointing upwards.

If you'd like to take cuttings, plant the tubers in a pot or tray of compost, with the old stems just above the surface. Grow them indoors in a heated propagator. Green shoots will quickly appear. These can be removed from the tuber when they're about 5cm (2in) long and used as cuttings. The tuber can then be planted in the garden as normal.

For extra plants, cut tubers into pieces before planting, ensuring each piece has a shoot.

Pot up cuttings as soon as they form their own roots. Grow them indoors, then plant them outdoors when the danger of frost has passed in late May or early June.

Pot up plants and place them in a sheltered area that's free from frost. In May, harden them off. Plant out between late May and June, depending when your last frost occurs.

After planting, pinch out the growing tip of each stem to encourage plants to bush out and form more flowers. Water regularly.

Stake plants with sturdy bamboo canes, being careful not to push the stake through the tuber.

Plants grow quickly and buds will soon appear, usually in groups of three. If you want dahlias for cut flowers or exhibition purposes, remove the two side buds. This will put the plant's energy into making the remaining flower. Once the flowers have faded, cut them off to encourage more to grow.

When the first frost arrives, cut back the stems to a few inches off the ground and dig up the tubers. Hang them upside down in a frost-free place for a few days, to help dry them out. Then store them in trays of dry compost for the winter. In mild areas, you can risk leaving them in the ground, although you may like to cover them with a layer of sand for extra protection.

Watch Sarah Raven's guide to planting tubers straight into the ground:

Slugs

These are only really a problem when plants are small, but it's best to use anti-slug remedies to avoid them munching through soft, new growth.

Earwigs

Perhaps the biggest problem for dahlia growers, this annoying pest eats the flowers. To trap them, try putting a pot filled with straw upside down on the top of a cane among the plants. Check it every day and empty out the earwigs hiding inside.

Diseases

Dahlia mosaic virus

Spread by aphids, this causes yellow blotches on the leaves and distorted foliage. The only cure is to burn your plants or take them to the tip. Watch out for aphids, and always clean any knives or scissors between plants to avoid spreading the disease.

Dahlia smut

This causes brown, round markings on the lower leaves. To avoid problems, don't grow dahlias in the same place each year.

Crown rot

This causes stored dahlia tubers to rot, and is frequently found on overwintered dahlia tubers. Check your tubers during the winter and separate out any that show signs of infection. This will stop the crown rot spreading to the other tubers. The best prevention is to dry the tubers out properly before you store them.

RHS Garden Wisley trials hundreds of dahlia varieties each year. They're on view in Portsmouth Field.
RHS Garden Wisley
Woking
Surrey GU23 6QB
Tel: 0845 260 9000
Website: www.rhs.org.uk

The National Dahlia Society organises shows around the country, where you can see dahlias at their best.
National Dahlia Society
48 Vickers Road
Ash Vale
Aldershot
Hampshire GU12 5SE
Tel: 01252 693003
Website: www.dahlia-nds.co.uk