Select a site with full sun and moist soil. Tall varieties should be sheltered from strong winds.
Plant canna rhizomes in spring after all danger of frost has passed and the soil has warmed. Prepare the garden bed by using a garden fork or tiller to loosen the soil to a depth of 12 to 15 inches, then mix in a 2- to 4-inch layer of compost. Dig a hole 4 to 6 inches deep. Set the rhizome horizontally in the hole, cover it with soil, and press firmly. Space rhizomes 1 to 4 feet apart, depending on the variety. Water thoroughly. In regions with short summers, start rhizomes indoors by potting up and placing them in a warm, sunny location.
Apply a 2- to 4-inch layer of mulch around cannas to retain moisture and control weeds. Cannas prefer consistently moist soil, so water plants during the summer if rainfall is less than 1 inch per week, and water container-grown plants frequently to keep soil moist. Stake tall varieties to keep them upright. Remove flowers as they fade. In autumn, after frost kills the foliage, cut plants back to 6 inches tall. Carefully lift each clump of rhizomes and put them in a plastic-lined box filled with perlite or peat moss, spacing them so that none are touching. Store boxes off the floor in a dry area at 45 to 55 degrees F. Replant in the spring.