Canna

Fundamental Facts

HARDINESS: Zones 7 to 11
PREFERRED SOIL pH: Adaptable
PREFERRED SOIL TYPE: Moist to wet
PREFERRED LIGHT: Sun
ATTRIBUTES: Large, colorful leaves and showy flowers; for beds, pots
SEASON OF INTEREST: Summer
FAVORITES: Large, colorful leaves and showy flowers; for beds, pots
QUIRKS: Thrives in damp or wet soil and humid heat
GOOD NEIGHBORS: Butter daisy, castor bean, crocosmia, daylily
WHERE IT GROWS BEST: Warm, humid climates in a sunny location
POTENTIAL PROBLEMS: Canna leaf roller, corn earworms
RENEWING PLANTS: Lives many years; divide crowded rhizomes in spring or early summer
CRITTER RESISTANCE: Good
PLANTING DEPTH: 2-3 in (5.1-7.6 cm)
SOURCE: Tubers, nursery plants
DIMENSIONS: 2-6 ft (0.6-1.8 m) tall; clumps to 6 ft (1.8 m) across

Canna in the Landscape

These vibrantly flowered Victorian favorites are back by popular demand. Cannas' arrow-shaped upright leaves, up to 2 ft (0.6 m) long, can be green, golden, or bronze or have multicolored stripes. Their crowning glory is their flamboyant, trumpet-shaped flowers in scarlet, yellow, salmon, or orange, which appear in midsummer. Cannas can grow in average garden soil, but because they prefer damp conditions, they are ideal for the edge of a pond or poorly drained spots. Few perennials can match cannas' endurance in sultry summers. In areas where they are not hardy outdoors, you can grow them in big containers, combining them with petunias, sweet potato vine, and other annuals.

All in the Family

Cannas have both showy foliage and exotic flowers. Fancy-leaved cultivars include 'Pretoria', which has yellow-and-green-striped leaves; 'Tropicana', with leaves striped in orange-red, peach, and green; and 'Wyoming', which is famed for its rich bronze foliage. If you want to focus on flowers, try 'Cleopatra', which has unusual red-freckled yellow flowers; 'Chinese Coral', with peach-colored blossoms; orange-red 'Lucifer'; and pale yellow 'Madame Butterfly'. A related canna with a less dramatic look is C. indica, or Indian shot. The flowers are smaller and usually red marked with yellow, while the green leaves may be stained with bronze or purple.

Growing Cannas

Cannas thrive in hot weather but cannot tolerate the cold. Plant cannas in spring after the last frost has passed. Lay the rhizomes on their sides about 2 in (5 cm) below the soil's surface, 12-18 in (30.5-45.7 cm) apart. Keep the soil moist until they sprout.

Occasionally small caterpillars, including canna leaf roller and corn earworms may chew holes in new leaves before they unfurl, creating a row of perforations when the leaves open. Overlook light damage or trim off damaged leaves. If the problem is severe, apply the biological insecticide Bt (Bacillus thuringiensis) as directed to control the caterpillars.

Treat cannas as perennials in Zones 7 through 11, but in colder zones the roots must be lifted and stored for winter. Dig them up after a hard frost has blackened the leaves and shake off any loose soil. Cut off old stems and let the rhizomes air-dry in a warm place. Pack the rhizomes in paper bags filled with dry peat moss, and store them for the winter at 40°-50°F (4°-10°C). Replant in spring as soon as the weather is settled and mild.

Increasing the Bounty

Cannas are easy to increase by division. Separate rhizomes in spring before planting, or dig and divide those growing outdoors in mild climates. Replant at the same depth at which the rhizomes previously grew.
In Zones 7 to 11 cannas grow so vigorously that it is wise to cut off old flowers to prevent reseeding and to monitor edges of the clumps to make sure the plants don't spread too far.