In spring, about six to eight weeks before the average date of the last frost in your area, remove the rhizomes from storage, split them into sections using a sharp knife, and make sure that each section has at least one good root and one good eye. Remove any damaged foliage and rotten plant pieces. Let the cut surface dry out for at least 24 hours before planting to prevent fungus. Plant each piece in a separate container of soil or planting mix until it's well rooted. Begin a regular watering and monthly feeding program with a 10-10-10 fertilizer. When all risk of frost has passed, transplant the young plants into the garden. (They may be transplanted as late as June, but then will only produce foliage, not flowers.)
Choose rhizomes that are thick (five or more centimetres) and firm and have at least one eye (growing point or crown).
• Cannas won't tolerate dry conditions, so water at least once a week. When cannas need water, their leaves begin to curl slightly.
• Choose a site where they will have at least four hours of full sun each day. The more water, fertilizer and bright sunlight they get, the bigger they will grow.
• Cannas do best in rich, moist soil with lots of added organic matter. Plant rhizomes 12 to 15 centimetres deep, laying them horizontally with eyes pointing up, then cover with about five centimetres of soil.
• Good air circulation is important, so space rhizomes 45 to 60 centimetres apart. Small or dwarf cultivars may be planted as close as 30 centimetres apart.
• Feed every two weeks during active growth with all-purpose, water soluble (20-20-20) fertilizer or once a month with granular bulb fertilizer.
• Deadhead to promote continuous flowering, being careful not to destroy developing buds.
• Because they're sturdy, there's no need to support canna stems, but they may need protection in windy locations to prevent leaves from becoming tattered.
• Cannas may be attacked by slugs or snails. The safest way to combat these pests is to pick them off by hand. Be extra diligent when the plant is young and more susceptible to these uninvited guests.