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.
Growing Guide
Step-by-step instructions for growing Cosmos
Planting Calendar
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Sow Seeds Indoors
Sow seeds in trays or modules from to , using of fine compost. Keep them at and just moist, not wet.
Prick Out Seedlings
Move seedlings on when they are large enough to handle, from to . Pot them into small pots and keep them growing in a bright, frost-free place.
Harden Off Plants
Acclimatise plants over days before planting out, from to . Put them outside in the daytime at first, then leave them out for longer each day so they do not check in cold weather.
Plant Out
Plant into free-draining soil from to , spacing plants apart. Water in thoroughly straight after planting and protect young plants from slugs and late cold snaps if needed.
Deadhead & Maintenance
Remove fading flowers regularly from to . 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.
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