Colourful dahlias make a welcome addition to the late-summer garden and will continue to flower until the first frost. While many dahlias are grown from tubers planted in May, you can also raise them from seed.

Colourful dahlias make a welcome addition to the late-summer garden and will continue to flower until the first frost. While many dahlias are grown from tubers planted in May, you can also raise them from seed.

Sown now in the greenhouse, dahlia seeds will produce young plants ready to plant outdoors in late May to flower this year. Seed companies sell a range of quick-growing bedding strains that are suitable for growing this way. You can also use this method for sowing seeds saved from your own dahlia plants at the end of the previous season.

How to do it

1. Fill a pot or seed tray with moist multi-purpose compost and lightly firm the surface. Sow dahlia seeds on the surface and push them gently into the compost. Don't forget to label your seeds.
2. Cover pots with an inflated clear polythene bag, held in place with a rubber band. If sown in seed trays, cover with a propagator lid. The seedlings are ready to pot up singly when the second pair of leaves appear (as shown).
3. By mid May the young plants will be ready to go outside. Harden them off for a week by standing them outdoors during the day and bringing them indoors at night. They can then be planted out in their flowering positions in the garden.

Tip: Allow a few dahlia flowers to set seed for collection at the end of September. Save them in an envelope over winter to sow in February. You'll get a wonderful mixture of different flower shapes and colours from the resulting plants.