Certain cool-season annuals, like mums, are also sometimes grown as perennials. Can I expect these plants to come back year after year?
Cool-season annuals are annual plants that prefer cool temperatures, growing best in spring or fall. Many are tolerant of a light frost often surviving down to 28°F or sometimes even 25°F with little damage to flowers or leaves.
Plants such as mums, coral bells, and black-eyed Susan are sometimes grown as perennials, but also grow well when treated as a cool-season annual. These species will not reliably over winter when planted in the fall. Fall planting does not allow sufficient time for root establishment therefore they don’t overwinter well. They are best treated as annuals when planted late in the season. Some species traditionally treated as annuals, like pansy, dianthus, and bachelor’s button, will frequently survive the cold winter temperatures when planted in fall and begin growing and blooming again in early spring. These plants often do not tolerate the warm temperatures of summer, however, often browning and dying in the heat. Because of this, they are not treated as perennials despite being winter hardy most years.