Sow outdoors where they are to flower. Prepare the ground well and rake to a fine tilth before sowing. Sow 20mm deep, in rows 30cm apart. For earlier flowering: Sow seed, 1cm deep, 3 seeds per 7.5cm pot, in free-draining, damp seed compost. Place at 20-29C until after germination. Gradually acclimatise to outdoor conditions before planting out after risk of frost. Before planting into containers, ensure plants are well rooted in their pots. Thin out to 15cm apart when the seedlings are large enough to handle.