Like many annual bedding plants, petunias thrive with lots of sun. At least six hours per day is preferable. The plants grows in light shade, but as a rule, the number of flowers is directly related to the amount of sunlight the plant receives.
Along with abundant sunshine, petunias need well-drained soil. In areas with clay soil, this requires amendment with organic material like compost or peat moss. Once established, the plants are fairly drought tolerant. Feed with balanced fertilizer about every three weeks during the growing season.
Petunias generally fall into one of four groups. Grandifloras feature large flowers and a mounding habit. Multifloras have smaller, more abundant flowers. Millifloras sport the smallest flowers of all and work well in containers. Ground-cover petunias spread rapidly and can cover large areas or cascade from hanging baskets.