Sow at 15-20°C (60-68°F) in pots or trays using a good quality compost, covering the seed lightly with a sprinkle of compost, or vermiculite. Place in a polythene bag or propagator and keep the compost moist at all times. Germination normally takes 14-21 days. When the seedlings are large enough to handle transfer into pots or trays and grow on in cooler conditions. When the risk of frost has passed, acclimatise them to outdoor conditions over 14-21 days before planting out in their final flowering positions, 30-38cm (12-15") apart.