Cannas (Canna)

Cannas belong to the Cannaceae family and have leaves resembling those of the banana. They are tropical and sub-tropical perennials, which is why they are not hardy in temperate or colder regions of the world. The cannas used in gardens today are mostly Canna x generalis. Cultivars range from dwarfs that grow only 2 feet (60 cm) in height to tall ones that attain a height of 8 feet (240 cm).

Cannas are valued mostly for their large tropical foliage and showy, brilliantly-colored flowers. The foliage is as ornamental as the flowers. It may be pure green, greenish blue, coppery to purplish, ruby, or variegated with stripes.

Care and culture

Cannas thrive best on sunny locations with well-drained, loamy soil rich in organic matter. Incorporation of well rotten manure or compost will improve the performance of cannas in almost any soil. For further addition of nutrients, fertilize them early in the spring and continue on a monthly basis. When cannas are grown in pots, the fertilizer used should be one-fourth the rate recommended for plants grown in ground beds.

The rhizomes may be planted 1.5 to 3 inches (4-8 cm) deep and 1-1.8 feet (30-45 cm) apart, depending upon whether dwarf or tall cultivars are used, two weeks before the last frost in early spring. Rhizomes may also be potted in small pots or wooden flats containing moist peat moss in early February to allow roots and shoots to grow and develop. These are then transplanted into beds after all danger of frost is past. Transplants handled in this manner will flower earlier than those from rhizomes that are transplanted directly into beds.

Dead heading

To assure continuous bloom, remove the part of the stem that bore flowers after the flowers have withered. Usually a second flowering shoot, growing from the node just below the terminal flower, will be halfway in bloom already. Remove this shoot also when its blooms are withered. Another flowering shoot will soon develop on the node below the second shoot. If the first pair of shoots is not removed, much of the nutrition will be used for the developing seeds, and the flower cluster on the third node usually will remain dormant.

Removal of the shoots channels the plants energy to the young flower clusters on the third or fourth node to develop and bloom. If the removal of spent shoots is followed religiously, cannas will bloom profusely for a long period of time. Finally, when all flowering shoots finish blooming, remove the entire stem and leaves at or slightly above ground level, since no more flowers will grow from these stems. This will reduce the leafy appearance and will permit more light for other developing and flower-bearing stems on the same clump. In addition, this will reduce crowding and competition for nutrients.

Propagation

Propagation is done by dividing the rhizomes containing meristematic tissue (2-3 eyes) before planting.

Overwintering

In most areas, cannas must be lifted and stored to prevent freezing. After digging, rhizomes should be spread out in a cool place, such as a garage, to dry for a day or two. When the cut ends are dry, remove all the dried roots and place the rhizomes in a flat or box. Cover with dry peat moss and store in a cool place in the garage at 55°F (12°C) is best.

To avoid excessive drying of the rhizomes, it is customary to cover the flat or box with a layer of cardboard or a plastic bag. If this is done, be sure to make several holes in the bag to allow some exchange of air for rhizome respiration.