Growing Cosmos from Seeds
Sow Cosmos indoors from mid March or 4-5 weeks before the last frost of the year, or outdoor after the last frost. Prepare pots or a tray with good seed compost and lightly water, then label according to variety. Sow seeds on the surface and press gently into the surface and cover very lightly with a seed compost or vermiculite. Keep the compost damp – a propagator or clear plastic seal bag will work well as it helps retain moisture. A temp of 18c – 25c is ideal.
Transfer seedling to small pots when large enough to handle and plant out from mid May. Treat Cosmos as an annual flower.