Cosmos in Gagingwell

Cosmos bipinnatus

Cosmos
Cosmos · Cosmos bipinnatus

A half-hardy annual grown for long-lasting, daisy-like flowers. In the UK it does best in a sunny, sheltered spot with free-draining soil, and it flowers freely from summer into autumn if you keep it deadheaded.

90 cm · Full Sun · Moderate Water

Add to garden

Calibrated to Gagingwell · last frost ≈ 18 May

Sow indoors April, plant out June. Frost risk October to May.
ActivityJanuaryFebruaryMarchAprilMayJuneJulyAugustSeptemberOctoberNovemberDecember
Sow indoorsNoNoNoYesNoNoNoNoNoNoNoNo
Plant outNoNoNoNoNoYesNoNoNoNoNoNo

Growing guide

Step-by-step instructions for growing Cosmos

  1. 01

    Sow Seeds Indoors

    3 Apr to 27 Apr

    Sow seeds in trays or modules from 3rd April to 27th April, using of fine compost. Keep them at and just moist, not wet.

  2. 02

    Prick Out Seedlings

    29 Apr to 13 May

    Move seedlings on when they are large enough to handle, from 29th April to 13th May. Pot them into small pots and keep them growing in a bright, frost-free place.

  3. 03

    Harden Off Plants

    4 May to 18 May

    Acclimatise plants over 15 days before planting out, from 4th May to 18th May. Put them outside in the daytime at first, then leave them out for longer each day so they do not check in cold weather.

  4. 04

    Plant Out

    1 Jun to 18 Jun

    Plant into free-draining soil from 1st June to 18th June, spacing plants apart. Water in thoroughly straight after planting and protect young plants from slugs and late cold snaps if needed.

  5. 05

    Deadhead & Maintenance

    9 Jul to 8 Oct

    Remove fading flowers regularly from 9th July to 8th October. This stops the plant setting seed too early and keeps it producing flowers until the autumn frosts. Tie in taller stems if the plants get blown about, and water during dry spells.

Companion plants

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

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 Cosmos to consider

Sensation Mixed

Tall, open plants with large single flowers in mixed colours. A very common bedding and cutting strain in UK catalogues.

Purity

Tall white-flowered plants with good stems for cutting. Reliable in a sunny border.

Sea Shells Mixed

Distinctive tubular petals and strong colour range. Good for a lighter, airy planting effect.

Sonata White

A shorter, compact type suited to pots and front-of-border planting. Useful where space is limited.

Cosmos guides by town

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