Cosmos

Cosmos in Bembridge

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.

Height90cm
SunlightFull Sun
WaterModerate Water

Growing Guide

Step-by-step instructions for growing Cosmos

Planting Calendar

Seed IndoorLater
J
F
M
A
M
J
J
A
S
O
N
D
TransplantLater
J
F
M
A
M
J
J
A
S
O
N
D
MaintenanceNow
J
F
M
A
M
J
J
A
S
O
N
D
  1. Sow Seeds Indoors

    16 Dec – 9 Jan

    Sow seeds in trays or modules from 16th December to 9th January, using of fine compost. Keep them at and just moist, not wet.

  2. Prick Out Seedlings

    11 Jan – 25 Jan

    Move seedlings on when they are large enough to handle, from 11th January to 25th January. Pot them into small pots and keep them growing in a bright, frost-free place.

  3. Harden Off Plants

    16 Jan – 30 Jan

    Acclimatise plants over 15 days before planting out, from 16th January to 30th January. 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. Plant Out

    13 Feb – 2 Mar

    Plant into free-draining soil from 13th February to 2nd March, spacing plants apart. Water in thoroughly straight after planting and protect young plants from slugs and late cold snaps if needed.

  5. Deadhead & Maintenance

    23 Mar – 29 Nov

    Remove fading flowers regularly from 23rd March to 29th 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.

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.

Also in nearby towns

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