When to plant Cosmos in Bath

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

Calibrated to Bath · last frost ≈ 24 Apr

Sow indoors March to April, plant out May. Frost risk November to April.
ActivityJanuaryFebruaryMarchAprilMayJuneJulyAugustSeptemberOctoberNovemberDecember
Sow indoorsNoNoYesYesNoNoNoNoNoNoNoNo
Plant outNoNoNoNoYesNoNoNoNoNoNoNo

Growing guide

What to do through the growing season

  1. 01

    Sow Seeds Indoors

    10 Mar to 3 Apr

    Sow seeds in trays or modules from 10th March to 3rd April, using of fine compost. Keep them at and just moist, not wet.

  2. 02

    Prick Out Seedlings

    24 Mar to 1 May Dates as each sowing reaches this stage

    Move seedlings on when they are large enough to handle, from 24th March to 1st May. Pot them into small pots and keep them growing in a bright, frost-free place.

  3. 03

    Harden Off Plants

    24 Apr to 8 May

    Acclimatise plants over 15 days before planting out, from 24th April to 8th 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

    8 May to 25 May

    Plant into free-draining soil from 8th May to 25th May, 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

    7 Jun to 2 Nov Dates as each sowing reaches this stage

    Remove fading flowers regularly from 7th June to 2nd November. 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.

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.