Dahlias are loved for their long flowering season, which often lasts until the first frosts, and come in a huge variety of flower colour and shapes. Grow them as part of a late-summer planting scheme or as a cut flower.
How to grow dahlias
Dahlias require a fertile, moist but well-drained soil, and a sunny, sheltered spot. Taller varieties need staking. In autumn, dig up the tubers and overwinter them in a frost-free place such as a greenhouse or a shed. Plant them back in the ground from May onwards.
More on growing dahlias:
Where to grow dahlias
How to grow dahlias – dahlias growing in a raised bed
Dahlias are easy to grow and unfussy when it comes to soil. For best results grow in any fertile, moist but well-drained soil in full sun, in a sheltered spot. If growing in pots, use a good quality, peat-free multi-purpose compost.
How to plant dahlias
How to grow dahlias – planting dahlia tubers
Dahlia tubers are available to buy from late February. Alternatively, buy potted plants from early summer.
Watch Alan Titchmarsh demonstrate how to plant dahlia tubers, in our No Fuss video guide:
When planting dahlias, dig a planting hole and add a bucket full of well-rotted organic matter, to increase soil fertility. Position tubers so they sit just below the soil surface. 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.
Plant potted dahlias at the same depth they were in the pot.
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.
How to care for dahlias
How to grow dahlias – overwintering dahlia tubers
In most parts of the country, dahlias will not overwinter if left in soil outside over winter. To prevent loss, lift the tubers once the foliage has been blackened by frost. Cut the stems back to about 12cm, then, 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 dark garage the perfect store. Leave them here until planting time in late spring.
If you don’t have the space to lift and store dahlia tubers, you can cover the soil with a thick layer of mushroom compost and/straw, to prevent frost from penetrating the tubers. In spring simply rake away the excess compost.
Here, Alan Titchmarsh demonstrates how to lift dahlias for winter:
In spring, once the plant has reached about 20cm tall, encourage more flowering sideshoots by pinching out the growing tips.
Deadhead dahlias in summer to prolong flowering. Here, Monty explains how to deadhead dahlias to prolong flowering:
Discover three Golden Rules of caring for Dahlias:
How to grow dahlias – taking dahlia cuttings
Dahlia 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. 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 set of 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
It’s also possible to grow dahlias from seed.
Growing dahlias: problem solving
How to grow dahlias – making an earwig trap
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 and placing 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.
Find out how to stop capsid bugs eating your dahlias, in our Quick Tips video:
Dahlia varieties to grow
How to grow dahlias – Dahlia ‘Arabian Night’
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