Sow Dahlia seeds indoors from February to April on the surface of a good, free draining compost and lightly cover with a fine sprinkling of compost or vermiculite. Place the seed tray in a propagator at a temperature of 20-25C (68-77F) or seal inside a clear polythene bag until germination which takes 7 – 21 days. Keep the compost damp but not wet and do not exclude light as this helps germination.
When seedlings are large enough to handle, transplant into 7.5cm (3″) pots and grow Dahlia plants on in cooler conditions. When all risk of frost has passed, gradually acclimatise to outdoor conditions over 7 – 10 days before planting outdoors. Plant Dahlias at a distance of 30cm (12″) apart on any fertile, well drained soil in full sun.