Canna lilies are not true lilies, but their large blooms resemble lily flowers. The plants produce 4-foot-tall flower stalks and large, banana-like leaves. Canna grow as perennials in areas with mild winters. In areas with winter freezing, canna grow in pots or they are dug up and stored each fall and replanted in spring. Proper pruning keeps the canna looking its best throughout the growing season and helps prepare them for dormancy and winter storage, when necessary.
Remove old flowers as soon as they wilt. Cut the stem ¼ to ½ inch beneath the spent flower head using a pair of shears. Repeat this process as each blossom down the flower stalk withers. Pruning in this manner, called deadheading, prevents the canna from setting seed and diverts nutrients to the unopened buds, encouraging them to bloom.
Cut out the entire flower stalk once all the shoots have finished blooming. Remove the stalk at the base of the plant. New stalks will grow in and replace the removed stalks over time, leading to further flowering.
Prune out dead or damaged leaves throughout the growing season. Cut these off the plant at the base of the plant or where they emerge from a flower stalk, using sharp shears. While dead leaves rarely stress the canna, they do make the plant unattractive when left in place.
Cut the entire plant back to within 6 inches of the ground in fall when it yellows and dies back. Die back usually occurs after the first fall frost in areas where frost occurs. Dig up the bulbs for winter storage after pruning off the foliage.