Gladiolus is an easy-to-grow flower noted for its tall flower spikes. The gladiolus or gladiola typically is grown in U.S. Department of Agriculture hardiness zones 7 through 10. Called the sword lily for its upright, flower-studded stalk, the gladiolus is a fair weather plant. The flower bulbs, also called corms, are not winter-hardy. The flowers bloom from mid-summer through the first frost.