Dahlia 'Doris Day'

How to grow dahlias

Discover all you need to know about growing dahlias, in this start-to-finish guide.

A table displaying which months are best to sow, plant and harvest.
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
Plant
Plant

Do not Plant in January

Do not Plant in February

Do not Plant in March

Do not Plant in April

Do Plant in May

Do Plant in June

Do not Plant in July

Do not Plant in August

Do not Plant in September

Do not Plant in October

Do not Plant in November

Do not Plant in December

Flowers
Flowers

Plant does not flower in January

Plant does not flower in February

Plant does not flower in March

Plant does not flower in April

Plant does not flower in May

Plant does not flower in June

Plant does not flower in July

Plant does flower in August

Plant does flower in September

Plant does flower in October

Plant does not flower in November

Plant does not flower in December

Cut back
Cut back

Do not Cut back in January

Do not Cut back in February

Do not Cut back in March

Do not Cut back in April

Do not Cut back in May

Do not Cut back in June

Do not Cut back in July

Do not Cut back in August

Do not Cut back in September

Do not Cut back in October

Do Cut back in November

Do not Cut back in December

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.

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More 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 extend the summer and often flower until the first frosts.

Dahlias in a raised bed
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
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

Propagating dahlias
Taking dahlia cuttings

Propagating dahlias

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

Overwintering dahlias
Overwintering dahlias

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.

Deadheading dahlias
Deadheading dahlias

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.

Video: Caring for dahlias – Golden Rules

Video: Lifting dahlias for winter

How to lift and store dahlias

No space to store 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 ‘Arabian Night’

Dahlia varieties to grow

  • 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
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Dahlias by colour