Set plants 15 to 18 inches apart. Choose a site in sun, nearly any soil will do, so long as it is well-drained.
Water plants during periods of drought. (If your summers tend to be hot and dry, a summer mulch will help conserve moisture.) Attention to deadheading will encourage the longest possible blooming season, and also prevent inferior seedlings. Cut back to the ground after blooms end, and apply a winter mulch after the ground freezes. Divide in spring or fall every 3 to 5 years, as needed to rejuvenate.