Canna Planting Guide
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.