Most annual flowers won't survive over the winter in cold climates, but many tolerate some frost. Some annuals, such as pansies, violas, and flowering kale, survive heavy freezes. Some hardy annuals to try include alyssum, lobelia, phlox, cornflower, dianthus, nasturtium, poppy, pot marigold, snapdragon, stock, and sweet pea. These plants perform best in cool weather and will bloom best in spring and fall. In midsummer, when temperatures are high, most of them will stop flowering. With the return of cooler temperatures in fall, they will begin to bloom again.