Dahlias extend the summer flowering season and often last until the first frosts. They’re popular as a cut flower and renowned for offering a huge variety of flower colour and shapes. These tuberous rooted perennials are ideal for gardeners who want to add vibrant colour to their plots late in the season.
More expert advice on growing dahlias:
Dahlia tubers are for sale from late February or potted plants are often sold in early summer.
Discover more about these impressive perennials, in our dahlia Grow Guide, below.
Dahlias in a raised bed
Where to plant dahlias
Dahlias are easy to grow and unfussy when it comes to soil. For best results grow in any fertile, well-drained soil in full sun, in a sheltered spot.
In mild parts of the UK dahlias will overwinter outside if the soil is well-drained. In most other areas it’s advisable to lift the plants. Store the tubers in a frost-free place after the first frost has blackened the foliage. The tubers are then replanted in the garden once all danger of frost has passed in the spring.
Planting dahlia tubers
How to plant dahlias
Start planting dahlia tubers in late May when frosty nights are coming to an end. Potted plants mustn’t be planted until all danger of frost has passed.
When planting in the garden, dig a planting hole and add a bucket full of well-rotted organic matter. Mix this in with the garden soil and make room for the tuber that should be positioned just below the soil. In containers plant into a multi-purpose compost.
It’s vital that you plant the tuber the right way up. Look for the old stem – this is the top. Once planted water in well. New shoots will start to form about five weeks after planting and these new shoots need protecting from slugs and snails. Either use a few slug pellets or go out at night with a torch and collect up these nocturnal enemies.
Dahlias are greedy plants, so apply a feed in July. July is also a good time to tie stems to stakes or use a plant support.
Video: How to plant out dahlias
How to plant tree dahlias
Taking dahlia cuttings
Tubers of a good size can be divided in spring. To do this press the tubers down onto a tray of shallow compost and leave them to start growth in a greenhouse or in a sunny room in April. Keep the compost warm and moist.
Once the tubers start to produce shoots divide them using a clean, sharp knife so that each section has at least one shoot and roots. Pot on the divisions and grow on to plant out once all danger of frost has passed.
Dahlias can also be propagated by taking basal cuttings in spring.
How to take basal cuttings from dahlias
Video: How to grow dahlias from seed
Dahlias: problem solving
Dahlias will not overwinter if left in soil outside over winter in most parts of the country. To avoid loss, lift the tubers once the foliage has been blackened by frost. Cut the stems back to about 12cm. With a garden folk, gently lift the tuber and remove the soil with your fingers. Place tubers upside down in a newspaper-lined tray so that they can dry out for a couple of weeks in a dry place.
Once dry, place the tubers in a cool, frost-free place in a shallow tray of dry compost or horticultural sand. Don’t water them. They don’t need light during this time, making a garage the perfect store. Leave them here until planting time in early summer.
Dahlias are prone to attack from earwigs. They’ll eat their foliage, buds and flowers. Create earwigs traps by pushing a garden cane into the soil by the plant and put an upturned garden pot stuffed with straw on top of it. During the day the earwigs will retreat to the pot and you can then dispose of them.
How to look after dahlias
Dahlias are simply cut back in autumn before storage. Or, if leaving them in the garden, once the flowers have passed and the foliage has been blackened by frost.
To encourage more flowering sideshoots the growing tip can be pinched out once the plant has reached about 20cm tall in spring.
Discover the three Golden Rules of growing dahlias, in this video featuring dahlia expert Michael Mann:
Watch our video guide to lifting dahlia tubers for winter, featuring Alan Titchmarsh:
No space to store dahlia tubers?
If you haven’t got the space to lift and store tubers then in autumn cover soil with a thick layer of mushroom compost. In spring simply rake away the excess compost.
Dahlia ‘Arabian Night’
Dahlia varieties to grow
Dahlia ‘Arabian Night’ – impressive large, fully double flowers with a deep burgundy colour
Dahlia ‘Bishop of Llandaff’ – semi-double, bright red flowers set against dark bronze foliage
Dahlia ‘Juliet’ – a dahlia with large, single purple flowers held over dark foliage
Dahlia ‘Indian Summer’ – a great performer with red, spikey cactus style flowers
Dahlia ‘Tahoma Moonshot’ – really dark, velvety purple underside to the petals that curl in over a yellow petal top. This single type is a real talking point
Dahlias by colour