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.
The gladiolus blooms on tall stems with narrow, blade-shaped leaves. Because glads mature in a season, you can plant corms in spring and enjoy flowers by mid-summer, when a series of trumpet-shaped florets opens along the stem. Plant the corms in well-drained, organic soil with moderate moisture. Encourage prolific blooms by planting gladioli away from shrubs or other tall flowers. The plants produce strong stems and healthier flowers with open exposure to sunlight. When the plants die back in late autumn, corms remain in the ground in temperate climates and put out new foliage and flowers in spring. Dig up corms in cold zones and store in a well-ventilated, protected area at 35 to 45 degrees Fahrenheit until spring.
Glads range from miniatures, growing under 3 feet tall with 2-1/2-inch flowers, to giants, growing 4 to 6 feet tall with 5-inch blooms. Glads flower in almost every color shade from white through dark purple. Some cultivars yield bi-color flowers, such as white with brown centers. Other hybrids offer green flowers that blend with the tall leaves. Miniatures fit well as cut flowers in small bouquets. Glads make spectacular vase arrangements with or without other cut flowers.
Keep flowers upright by staking gladioli. In wind or rain, glads may topple, uprooting the bulbs. Flower weight makes some glad stems bend or break. Protect stems by staking each individually or staking a row of glads. Stake individual flowers by tapping a 1-inch square wood support into the ground and tying each stem to its stake. Support a row of glads by tapping in 2-inch square posts and weaving twine between the posts. Tie the glads to the twine network. Some gardeners plant rows of glads in front of lattice so that tipsy glads are easily anchored to the decorative lattice grid.
Select cultivars that bloom at different times for an ever-changing summer display. By planting corms in succession every two weeks from spring through early summer, the glads bloom continuously into autumn. For variety, choose a different color or height for each planting.