Sensation Mixed
Tall, open plants with large single flowers in mixed colours. A very common bedding and cutting strain in UK catalogues.
When to plant Cosmos in Cambridge
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 Cambridge · last frost ≈ 7 May
| Activity | January | February | March | April | May | June | July | August | September | October | November | December |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Sow indoors | No | No | Yes | Yes | No | No | No | No | No | No | No | No |
| Plant out | No | No | No | No | Yes | Yes | No | No | No | No | No | No |
Growing guide
What to do through the growing season
01
Sow Seeds Indoors
23 Mar to 16 AprSow seeds in trays or modules from 23rd March to 16th April, using of fine compost. Keep them at and just moist, not wet.
02
Prick Out Seedlings
6 Apr to 14 May Dates as each sowing reaches this stageMove seedlings on when they are large enough to handle, from 6th April to 14th May. Pot them into small pots and keep them growing in a bright, frost-free place.
03
Harden Off Plants
7 May to 21 MayAcclimatise plants over 15 days before planting out, from 7th May to 21st 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.
04
Plant Out
21 May to 7 JunPlant into free-draining soil from 21st May to 7th June, spacing plants apart. Water in thoroughly straight after planting and protect young plants from slugs and late cold snaps if needed.
05
Deadhead & Maintenance
20 Jun to 19 Oct Dates as each sowing reaches this stageRemove fading flowers regularly from 20th June to 19th 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.
Suggested varieties
Popular varieties of Cosmos to consider
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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Cosmos guides by town
See how Cosmos timing shifts in other towns with different frost dates.