Cooler-zone gardeners are discovering that with a little wintertime care, plants that have long been considered "annuals" can thrive for years. These plants - including geraniums, gladioli, dahlias, begonias, rosemary, lavender, snapdragons, and even impatiens - aren't annuals at all. Rather, they are tender perennials. They aren't hardy enough to survive winter on their own, but they can be moved indoors during the cold months and then returned to...