Petunias, native to south America, produce blossoms in a variety of shades, including bi-colored. In most areas of the United States, petunias are grown as annual plants because their specific needs prevent them from surviving winter weather. With proper care, petunias will keep all year.
Plant petunias in well-drained soil. Do not use moisture-retaining potting soil, as this leads to root rot.
Water the petunia when the top inch of soil feels dry to the touch. Petunias are drought-tolerant and prefer their soil to be on the dry side.
Fertilize every two weeks with a balanced, water-soluble fertilizer. The best concentrations for petunias are 8-8-8, 10-10-10 and 12-12-12.
Keep the plant in full sunlight for at least 6 hours each day. In the south, reduce the light to filtered light or fewer full-sun hours because of the scorching temperatures.
Move the petunia indoors when the weather drops to 60 degrees F during the day. Petunias do not like cool weather, and will wither when exposed to the cold for too long.
Provide light indoors with a bright, sunlit window that receives at least 8 hours of sunlight each day. Alternately, if there are no brightly-lit windows, use a grow light or bright, unshaded lamp.