How To Grow: Cosmos

This group of plants in the Asteraceae family are commonly called the Mexican aster and, although perennial in its native home of Mexico and parts of North America, it is not hardy in Britain and so is used as a garden annual.

Picture courtesy of Kazba!

Cosmos come in a wide range of colours, flowers shapes and heights, though the most common colours are pink, white or purple and less commonly, orange. They are easy to grow from seed making them a favourite plant for amateur gardeners and professionals alike. Cosmos grow easily in most garden soils but favour neutral to slightly alkaline conditions. Grow them between perennial plants or in bedding schemes in groups, rather than alone, not just for impact but to help hold each other up.
Here are our gardening tips on how to grow cosmos in your garden this year:

1. Select seeds from a reputable source, this could even be seed you saved or collected yourself. The seeds are long and thin, so can be easily handled, and need to be planted into modules with compost. Plant the cosmos seed in the middle of the module just below the surface of the compost, water in well and place in a greenhouse or warm windowsill to help germination.

2. When large enough to handle and the risk of frost has past, plant out in your garden into soil that has been improved with manure or garden compost. Plant the cosmos in full sun and water well, then add a mulch to help conserve moisture.

3. Stake and tie plants if necessary during the growing season and don’t forget to water regularly.

4. Cosmos will flower till the first frosts if you regularly dead head the plants and feed with chicken manure or blood, fish and bone.

For more advice on how to grow your favourite flowers in your garden, visit our gardening tips page.