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Plant of the month: Cosmos

Frothy, bee-friendly, versatile and fun to grow. Sounds like a perfect garden filler...

Cosmos 'Cosimo Pink-White' on the Trials Field at WisleyBrightly coloured, long-lasting and easy to grow, cosmos is a popular garden flower. It’s great for the gardener, and popular with bees.

This year Fleuroselect, the international organisation for the ornamental plants industry, has designated 2016 as “The Year of the Cosmos”. As a result, and because we love it anyway, we have a large number of them in the garden.
Cosmos is a versatile garden plant used in beds, borders and containers to give summer colour. They make good cut flowers, best harvested when the buds are two thirds to three quarters open, and if you use cut flower food you can extend the vase life up to 14 days.
The ferny foliage of Cosmos bipinnatus makes them a winner too (Cosmos sulphureus is slightly less frothy). It adds a lovely contrast amongst other bedding plants with larger leaves. You can see this in our Cutting Garden, where they’re planted among a plethora of plants. On the Top Terrace, where we pay homage to Major Tim Peake with our Rocket Science display, we’re using cosmos (well, you would, wouldn’t you) as one of the plants in the moonscape, along with grasses, antirrhinums, zinnias and airplants on stakes to represent planets. It’s very pretty.
The best place to compare and contrast is on the Trials Field this summer. There’s an abundance of cultivars based on Cosmos bipinnatus and C. sulphureus, with a height range of approximately 20 to 120cm (8in to 4ft). Something for every situation then, and in all sorts of colours. We have pure whites to deep pinks, beautiful yellows plus bicoloured flowers, some frilly, others curled. 
Want to know more? Almost all species of Cosmos originally come from the meadows and scrublands of Mexico. The wider distribution includes the USA, Central America and South America, and today cosmos have naturalised across many parts of the world. They thrive in poor soils in temperate areas, and enjoy warm weather and full sun. We can expect them to flower until the first hard frost.

See also

Read about a revolutionary new yellow cosmos

See plantsman Graham Rice's new plants blog about exciting developments in chocolate cosmos breeding

Get involved

The Royal Horticultural Society is the UK’s leading gardening charity. We aim to enrich everyone’s life through plants, and make the UK a greener and more beautiful place.