Cosmos flowers are a self-seeding annual, according to About.com's flower expert Jamie McIntosh. Cosmos flowers are tough and pest-free plants that give a burst of color.
Cosmos flowers are part of the Aster family of plants and grow from 1 to 5 feet high, depending on the cultivar. It is a frost-free annual in all USDA hardiness zones. Planting in full sun will result in many blooms from early summer until the frost. There are several colors available of cosmos, which are ray-flowers like daisies unless they are doubled, in which case they look like carnations. Cosmos blooms are easy to grow.