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 and central America – especially Mexico.  For cutting, blooms are best harvested when buds are two-thirds open – and flowers can last in vases up to 14 days when cutflower food is used.  Cosmos can also be grown in pots to great effect.

Cosmos prefer poor soil, so little preparation is needed.  Tolerates many soil types – which may be why it’s used to great effect along beautiful 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.

Cosmos interplanted with lobelia, dug over and planted mid-June 2018.

  • Plants can self-seed, effectively creating an established bed.  (Other plants that are prone to self-seeding including dill and coriander.)


  • Once established, cosmos need little water and no fertiliser.


  • Might be worth considering staking plants.


  • Cosmos are an important source of nectar for butterflies.


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.