Sow March to June outdoors where they are to flower once the soil has warmed. Prepare the ground well and rake to a fine tilth before sowing. Sprinkle the seed thinly over the surface, then rake lightly to ensure seed is just covered. Alternatively, sow 1.5mm (1/16in) deep in drills, 30cm (12in) apart. Germination usually takes 14-21 days.
As seedlings germinate, carefully thin out any that are too close together with a trowel and replant elsewhere.
Regular removal of spent flowers will encourage further blooming.