Cosmos in New Grimsby

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 New Grimsby · last frost ≈ 19 Feb

Sow indoors January, plant out March. Frost risk December to February.
ActivityJanuaryFebruaryMarchAprilMayJuneJulyAugustSeptemberOctoberNovemberDecember
Sow indoorsYesNoNoNoNoNoNoNoNoNoNoNo
Plant outNoNoYesNoNoNoNoNoNoNoNoNo

Growing guide

Step-by-step instructions for growing Cosmos

  1. 01

    Sow Seeds Indoors

    5 Jan to 29 Jan

    Sow seeds in trays or modules from 5th January to 29th January, using of fine compost. Keep them at and just moist, not wet.

  2. 02

    Prick Out Seedlings

    31 Jan to 14 Feb

    Move seedlings on when they are large enough to handle, from 31st January to 14th February. Pot them into small pots and keep them growing in a bright, frost-free place.

  3. 03

    Harden Off Plants

    5 Feb to 19 Feb

    Acclimatise plants over 15 days before planting out, from 5th February to 19th February. 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

    5 Mar to 22 Mar

    Plant into free-draining soil from 5th March to 22nd March, 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

    12 Apr to 3 Dec

    Remove fading flowers regularly from 12th April to 3rd December. 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.