by Connie Oswald Stofko When you have a mixed container of annuals that includes flowers such as petunias, the plants are supposed to be in a tall, rounded mound with no flat spots. If yours don’t look like that, you’re probably watering wrong, said Jen Weber, vice president and manager of Mike Weber Greenhouses, 42 French Rd., West Seneca. To water prevent holes and flat spots, use a watering can and water slowly. If you have a spikey flower in the center…