Perennial plants come back year after year, sometimes for 10 or 20 years. For gardeners, this means they plant once and enjoy the beauty for years to come. Annual flowers complete their growing cycle in one season and then die. Many gardeners plant both perennials and annuals. Direct Gardening offers a wide selection of perennials including sun-loving perennials and shade-loving perennials. Some perennials, like ferns and hostas, are grown primarily for their foliage. Others, like daylilies, iris and coneflowers, are treasured for their flowers. When buying perennials for sale, take into account the plant's mature height and spread, sunlight and soil requirements, foliage or flower colors, bloom times and other maintenance needs.