Plant seeds outdoors in the spring (in areas with mild winters, sow seeds in the fall). Choose a site with full sun to light shade and well-drained soil. Place seeds about 9 inches apart, and cover very lightly with a thin layer of soil. Water.
Keep seeds moist, but don't over-water. Germination should take about 10 days.
To plant nursery-grown plants, space them 9 to 15 inches apart. Stock plants can be planted in the spring. Dig a hole to accommodate the plant, cover with soil, compact to remove any air pockets, and water. Water regularly until established.
Snip off spent blooms to increase flowering. Clip off blooms right below the flower head.
Fertilize once a month with the fertilizer of your choice.