Sow indoors, February-April, in pots or trays of seed compost. Maintain gentle warmth and keep the compost moist, but not saturated. Thin (prick out) to other trays when large enough to handle. Harden off before planting out, late May, allowing 23cm (9") between plants. Or outdoors, April-May, in flowering position. Thin seedlings if necessary. Flowers: June to October. Remove dead heads to prolong the flowering season.