Petunias are a one season annual but that doesn't mean you can't keep them in bloom for a whole year - with the right weather and continuous feeding and most important of all, continue to deadhead or remove the faded buds so the plant does not need to put any energy into making seed. Pinch back the stems when they get leggy and your petunia will be long lived for several more months. Then, add it to the compost pile and start with fresh plants in the spring. Keep growing, Marianne Binetti