Cosmos have fresh, fern-like foliage and a long flowering season. They also make fine cut flowers.
They are members of the daisy family (Asteraceae) and are native to southern & central America – especially Mexico.
For cutting, blooms are best harvested when buds are two-thirds open. Flowers can last in vases up to 14 days when cut-flower food is used.
Cosmos are easy to grow in any sunny spot and can also be grown in pots to great effect.
Cosmos prefer full sun and poor soil, so little preparation is needed. They can tolerate many soil types – which may be why it’s used to great effect along motorway verges in France and continental Europe.
- Cosmos are easy to start from seed. Rake through beds removing rocks and weeds, and direct sow.
- Direct sow under cloches March-April, or without protection in May-June.
- Plants can self-seed, effectively creating an established bed. (Other plants that are prone to self-seeding include borage, dill, coriander and love-in-a-mist.)
- Once established, cosmos need little water and no fertiliser.
- Deadhead regularly to encourage continuous flowering.
- It is worth considering staking plants if you have very high growing types.
- Cosmos are an important source of nectar for butterflies and are loved by bees and other pollinators.
According to Maggie Campbell-Culver in her The Origin of Plants, Cosmos were first introduced to Britain from Spain (from Mexico) on request of the Marchioness of Bute in 1799. They subsequently fell out of favour with British gardeners, only recovering favour at the very end of the twentieth century. (The Origin of Plants, p.298)
We planted two cosmos – a hot deep pink and a white – into the allotment early June 2018. We forked over and created a new slender flower bed along the front edge of the holly hedge and heading towards the front boundary and the shade of the fig tree, which grows in our adjacent neighbour’s plot to the front.
Summer 2019 we planted pink cosmos late (after our return from holiday in Canada (Toronto, Edmonton, Banff, Gibsons Landing BC). They were still in flower in early November 2019!
Summer 2020 we planted a low-growing white cosmos into the allotment flower bed.
Cosmos are a favourite with bees, so are really great as a companion plant to vegetable growing beds.