A longtime favorite of gardeners, gladiolus add vertical interest and showy color to the late season garden. The colorful flower spikes also look gorgeous in cut-flower displays. Gladiolus are grown from corms, often called bulbs, that are planted in the spring. Flowers usually bloom about 90 days after planting. Like other flower bulbs, gladiolus bulbs like well-drained soil and full sun to partial shade. Because some varieties can grow 5 ft. tall, they may require staking. Gladiolus are tender bulbs, meaning they aren't winter hardy and many varieties must be dug up or lifted in the fall in zones 3-7. Another option is to grow gladiolus as annual flowers.