Canna lilies are tropical to subtropical plants that are hardy to USDA gardening zone 8. Many gardeners in cooler zones grow the plants as annuals and replace them each year. There are many varieties of cannas. Some are dwarf, growing only to about 18 inches. Others grow to 10 feet high in their native habitat, but most in the United States average between 4 and 6 feet. Cannas have large leaves that look like banana leaves and bright-colored flowers that will bloom almost year round in places like South Florida.
Keep canna lilies in full sun. They will do well in large planters as well as the ground as long as they are not completely shaded. Some afternoon shade in the southern part of the hardiness zones will be fine.
Water the plants to a depth of 6 inches or more twice a week if there is no rain. You may need to water three times a week if the plants are in containers and it is very dry.
Place an inch of well-rotted manure on the top of the soil surrounding the stem when it starts to grow. Water well to leach the manure into the soil. Do the same with an inch of compost in mid-summer.
Apply time-release fertilizer to the soil in the spring. Use an eight-month release to fertilize the plant for the entire growing season. Follow manufacturer's directions on how much to apply.
Cut off flowering stalks when the flowers have faded. This will allow the energy to go to the next bloom. As each one is cut, another will come up throughout the growing season.
Lift the rhizome out of the soil in the fall if you are not in part of the hardiness zone. Cut all the stems back to 2 or 3 inches and allow the rhizome to dry out. Place the rhizomes in a container and put them in a cool, 40- to 50-degree, room or garage. Keep them dry until you are ready to replant in the spring.