When you buy your transplants, select a flat in bloom to guide you for color, and then buy the flat of that variety not yet in bloom. These will adapt more readily to your bed. Space the multifloras, grandifloras and floribundas about 10 inches apart. Space the spreading petunias like Purple Wave 20 inches apart and the millifloras 6 to 10 inches. Spread a good layer of mulch around the plants to prevent mud from spattering on the flowers, to retain moisture and to discourage weeds.
Petunias have many uses in the landscape.
Edge a perennial border with the compact millifloras or floribundas. Plant them on the ends of vegetable gardens and around those growing on trellises. There bright color will look great in contrast to the green leaves of the vegetables. Recommendations on this web site do not endorse any commercial products or trade names.