Canna lilies are flowering perennials related to banana plants. These tropical plants have herbaceous foliage with large lily-like flowers. Cannas should be cut back by deadheading individual flowers, pruning after flowering and removing foliage before winter.
Canna lilies bloom in summer. The large-leaf tropical plant produces stalks of flowers. The plant will bloom profusely all summer if dead or dying flowers are promptly removed. As each flower fades, the flower and stem are cut back to the next bud or bloom. Each flower stalk may yield several blooms in succession.
When the flower stalk is finished blooming, the stalk and leaves are cut back near the ground. This encourages new leaves and flower stalks from the plant clump. During the growing season, diseased flowers and leaves are removed by trimming them off at ground level.
Canna lilies die back in frost zones. Some gardeners trim off foliage just before or after frost and mulch the cannas for winter protection. In cold zones, the University of Nebraska recommends cutting the stems back to 4 inches above the ground. Dig up the rhizomes and store them over winter at 45 to 50 degrees F.