Choose a location in full sun or light shade with well-drained, slightly acid soil. Seeds can be planted outdoors directly where they are to be grown or in pots. The seeds are very fine and need to be covered by only a dusting of soil. Space the plants at 4-inch intervals when they are 1-2 inches high. Flowers bloom over a long season beginning about 8 weeks after seeds are sown. In warm zones they can be planted all year, and in cool zones they should be planted in the spring.
Water the plants regularly until established. Once they are doing well they will tolerate dry spells. After the first flush of flowers, shear the plants to induce a second flush. If plants begin to sprawl or become untidy, pull them out and shake them over the ground. You’ll find fresh seedlings emerging in a couple of months.