Cannas are tall perennials with giant leaves and clusters of flowers at the top of their stems. Their leaves can be striped or plain, depending on the variety. They command attention planted in groups in the perennial border. Difficult to grow from seed, cannas are widely available as rhizomes for planting in late spring. Because they are native to the tropics, they must be dug and stored over winter in all areas except those that are frost free.
Pick a spot in your garden with rich soil that gets sun at least eight hours per day. Do not plant where puddles remain after a rainstorm.
Spread 2- to 4-inches of peat moss and compost on the soil in the area where you are planting your cannas. Incorporate these into the soil by digging with a garden shovel or rototiller. Rake the soil smooth.
Plant canna rhizomes 2- to 3-inches deep and 12- to 36-inches apart, depending on the variety. Dig individual holes with your garden trowel, and place the rhizomes in the planting hole with the eyes facing up. Back fill the hole and firm the soil gently with your hands.
Water the entire bed with a lawn sprinkler when all of the canna rhizomes have been planted. Continue to provide cannas with the equivalent of an inch of rainfall per week.
Apply a 4- to 6-inch layer of mulch. Organic mulch such as wood chips or shredded bark is preferred because the mulch will help enrich the soil as it breaks down.
North of USDA Zone 9, dig the rhizomes in fall and store in a cool, frost-free location over winter. In Zone 9 and further south, mulch the ground after the foliage dies down to protect from cold winter weather.
Fertilize every three weeks during the growing season by spraying the foliage with water-soluble fertilizer, following the manufacturer's application instructions. In addition, for cannas left in the ground, scatter slow release granulated fertilizer around the base of the plants when the stems are 4- to 6-inches high. For cannas dug and stored in northern areas, add a teaspoon of granulated slow release fertilizer to the planting hole when re-planting in spring after all danger of frost has past.