Cosmos are sun-loving plants with a long flowering season. They fill borders with a profusion of flowers, ranging in colour from white through to pink, red and orange, in contrast with masses of feathery foliage. Shorter varieties also look good in containers and all cosmos make fantastic cut flowers. The simple open flowers are guaranteed to brighten up any garden well into autumn, and pollinators like them just as much as gardeners do.

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How to grow cosmos

Grow cosmos in moist but well-drained soil in full sun. Deadhead to prolong flowering and lift in autumn, after the first frosts. Save seed from spent blooms to sow the following season.

More on growing cosmos:


Where to grow cosmos

Pink cosmos
Pink cosmos

Cosmos are native to Southern and Central America and therefore need to be planted in a warm, sunny spot. Soil should be free-draining.


How to plant cosmos

Potting on cosmos seedlings
Potting on cosmos seedlings

Sow seed in early spring directly into the soil where you want your cosmos to grow, or into small pots or modules filled with free-draining seed compost. If growing in pots, pot on seedlings when they are large enough to handle. Plant out in late April/May after the danger of frost has passed.

Watch Monty Don plant out cosmos for a late summer display:


How to care for cosmos

How to grow cosmos - how to care for cosmos
How to grow cosmos - how to care for cosmos

Once your seedlings have formed 2-3 pairs of leaves, you can pinch out the growing tips to produce bushier plants with more flowers.

Taller varieties may need staking. Otherwise all varieties will flower for a long period if deadheaded regularly and fed with a liquid fertiliser. When deadheading, cut the stem back to the first leaf beneath the flowerhead.

The perennial chocolate cosmos varieties will need winter protection. Place them in pots until they've finished flowering, then shelter over winter in a frost-free place until spring.

Here, Monty Don explains how deadheading spent flowers will keep them blooming for as long as possible:


How to propagate cosmos

Collecting seed from cosmos seedheads
Collecting seed from cosmos seedheads

You can collect seed from flowering cosmos and save for next year. Or if you're growing chocolate cosmos, you can divide the tubers when you lift the plants for storage over the winter months.


Growing cosmos: problem solving

Planting out cosmos seedlings
Planting out cosmos seedlings

Cosmos are pretty much trouble-free to grow, apart from the threat of slugs and snails when seedlings are young and tender.


Great cosmos varieties to grow

Cosmos 'Sonata White'
Cosmos 'Sonata White'
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