Seed-saving

Let a few flowers go to seed at the end of the season. The dry brown seed heads can be picked when the petals have long dropped — store in a paper envelope, labelled.

Cosmos cross between varieties readily, so saved seed gives unpredictable but often beautiful new mixes. If you want a particular colour to come true, grow only that one variety in your garden.

Cosmos seed stays viable for 3–4 years if stored cool and dry. Don't refrigerate — paper envelope in a kitchen drawer is ideal.