Dahlias in Glaschoil

Dahlia pinnata

Dahlia
Dahlia · Dahlia pinnata

Show-stopping tuberous perennials that provide a spectacular display of colour from mid-summer right up until the first frosts. Ranging from enormous 'dinner plate' blooms to intricate pompoms and open-centred varieties that bees adore, they are a staple of the late summer UK garden.

100 cm · Full Shade · High Water

Calibrated to Glaschoil · last frost ≈ 10 Jun

Sow indoors April to May, plant out May to July. Frost risk August to June.
ActivityJanuaryFebruaryMarchAprilMayJuneJulyAugustSeptemberOctoberNovemberDecember
Sow indoorsNoNoNoYesYesNoNoNoNoNoNoNo
Plant outNoNoNoNoYesYesYesNoNoNoNoNo

Growing guide

Step-by-step instructions for growing Dahlia

Growing guide for

Change the guide to see different planting timelines and tips.

The most common UK method, starting tubers indoors in spring and planting out after frosts for summer blooms.

  1. 01

    Start Tubers Indoors

    29 Apr to 13 May

    Place tubers in trays with moist compost, eye-side up, and cover lightly. Keep at in a bright spot indoors from 29th April - 13th May. Water sparingly until shoots appear.

  2. 02

    Pot On Shoots

    27 May to 3 Jun

    Once shoots are tall, pot each tuber into individual containers with multi-purpose compost from 27th May - 3rd June. Grow on in a bright, frost-free place.

  3. 03

    Harden Off Plants

    17 Jun to 24 Jun

    Gradually acclimatise plants to outdoor conditions over 10-14 days from 17th June - 24th June. Place outside during the day and bring in at night, avoiding frost.

  4. 04

    Plant Outdoors

    24 Jun to 8 Jul

    Transplant into well-drained, fertile soil in full sun after frosts from 24th June - 8th July. Space plants apart and water in well. Use fleece if cold nights are forecast.

  5. 05

    Support and Pinch

    8 Jul to 15 Jul

    Insert stakes at planting to support tall stems. Pinch out the growing tip when plants reach to encourage bushiness from 8th July - 15th July.

  6. 06

    Feed and Water

    15 Jul to 7 Aug every 2 weeks

    Water regularly to keep soil moist, especially in dry spells. Feed every 14 days with a high-potash fertiliser from 15th July to boost flowering. Stop feeding by 7th August.

  7. 07

    Deadhead Regularly

    14 Aug to 26 Aug

    Remove spent flowers weekly from 14th August to encourage continuous blooms. Cut back to a leaf joint to promote new buds.

  8. 08

    Lift and Store Tubers

    28 Aug to 11 Sept

    After the first frost blackens foliage, cut stems back and carefully lift tubers from 28th August - 11th September. Dry, label, and store in frost-free conditions in dry compost or sand over winter.

Companion plants

Tap a plant to see why it works (or doesn't) with Dahlia.

Good companions

Plants to avoid

Why companion planting matters

Companion planting can deter pests, improve pollination, and make better use of space. Some plants confuse pests or attract beneficial insects; others improve soil or offer shade to neighbours that need it.

Suggested varieties

Popular varieties of Dahlia to consider

Bishop of Llandaff

A classic variety with dark foliage and bright red flowers, ideal for borders and excellent for pollinators.

Café au Lait

Popular for weddings, with large, creamy-pink blooms that can reach up to 25cm across.

Happy Days

A compact bedding type, perfect for containers, with prolific flowering in mixed colours.

Dahlia guides by town

See how Dahlia timing shifts in other towns with different frost dates.