Canna lilies (Canna indica) are beautiful and very easy to grow, but they're not for gardeners who favor subtlety. Cannas are generally huge with large showy flowers, and they make a visual statement with an exclamation mark. Canna leaves are wide and long (resembling banana leaves) in greens, bronzes, or variegated/ striped patterns. Watching canna leaves shoot up and then unfurl over a few days is an impressive sight. Flower colors range from yellow to orange to nearly black or neon pink. Most cannas grow up to 6 feet tall, occasionally as tall as 8 feet. They are good-humored plants, not demanding much care.
These plants grow from rhizomes and are hardy in zone 7 and warmer climates. In cooler climates, there are several ways you can still enjoy them: They can be grown as annuals, planted anew each spring; the rhizomes can be dug up each fall and stored indoors until spring planting time; or they can be grown in large pots that are moved to an indoor location when the weather turns cold.
The sheer size of cannas makes them most appropriate to the background of large planting beds where they can be blended with other large-scale plants. They also work well in very large mixed containers, such as barrels, where they can serve as the "thriller" component surrounded by other plants.
|Botanical Name||Canna indica|
|Common Names||Canna lily, canna|
|Plant Type||Rhizomatous perennial|
|Mature Size||4 to 8 feet tall, up to 5 feet in spread|
|Sun Exposure||Full sun|
|Soil Type||Rich, water-retentive, and well-draining soil|
|Soil pH||6.5; but tolerates a wide range|
|Bloom Time||Early summer|
|Flower Color||Yelllow, orange, pink|
|Hardiness Zones||8 to 12, USDA|
|Native Areas||South America, Central America, West Indies, Mexico, and the Southeastern United States|
How to Grow Cannas
In the garden, plant canna rhizomes horizontally, 5 to 6 inches deep, and cover them with a thick layer of mulch. Allow plenty of space around the rhizomes. These plants do not like to be crowded, and if other plants encroach, they may refuse to bloom. Keep the plants well-watered. Remove the flower stems immediately after they bloom. In fall, cut the plants down to ground level. In cooler climates, dig up the rhizomes for winter and pack them in peat moss or vermiculite before storing them in a cool, dry location at temperatures no lower than 40 degrees F. Canna rhizomes can get very large and overgrown; they will need to be lifted and divided at least every three or four years—more often if you want to propagate them.
When planted in pots, use a large container (15 to 18 inches across) with good drainage and a rich potting soil heavy with organic material. Plant the rhizomes horizontally, 4 to 5 inches deep, with eyes facing up. When grown in containers, cannas usually remain less than 5 feet tall. In cold climates, outdoor containers should be moved to a location that gets no colder than 40 degrees F. for the winter.
These plants prefer full sun but will survive in partial sun with some extra care to monitor the soil conditions (avoiding overly moist soil). Partial shade may also impact the color of the plants, making the leaves and flowers less vibrant.
Cannas will thrive in a variety of soils. They prefer rich, well-draining soils that are high in organic matter. Soil pH of about 6.5 is ideal, but cannas tolerate a wide range of acidic to alkaline soils.
The soil should be kept uniformly moist but should well-drained; otherwise, the rhizome may rot. In drier climates, give these plants at least 1 to 2 inches of water per week.
Temperature and Humidity
Cannas do well in high temperatures—and the more sun, the better. They thrive in temperatures up to 90 F. These plants are native to tropical zones, so they do well in humid conditions. In dryer environments, they are usually planted in moist environments, such as rain gardens, though soils must still be well-drained.
Canna lilies are known to be heavy feeders. Use plenty of compost or organic fertilizer to keep the plant happy. As long as you use organic materials, you cannot over-fertilize a canna lily plant. Feed in early spring, then monthly, using a balanced 10-10-10 fertilizer.
Growing in Containers
Cannas are large plants, so bigger is better in terms of choosing planting containers. Choose a pot that is at between 15 and 18 inches in diameter. This is not only for aesthetic reasons; it also increases your chances for large healthy plants, and it prevents the pots from tipping over.
Propagating Canna Lilies
Canna lilies can be propagated from seeds, but the more common method is to lift and divide the rhizomes. Fall or early spring is the best time to divide cannas.
- Dig up the entire mass of rhizome and cut off stems to about 1 inch.
- Brush off soil to expose the joints where new rhizomes sprout off the old rhizomes.
- Use a sharp knife to slice the rhizome segments apart. Each section should have at least one eye.
- Replant the pieces about 6 inches deep, allowing at least 2 feet between the segments.
Varieties of Cannas
There are hundreds of varieties of cannas, ranging in color and size. Some popular varieties include:
- 'King Humbert': originated in 1902 and has dark, bronze-purple foliage and red flowers
- 'Shenandoah': bears deep pink flowers over burgundy leaves
- 'Tropicana': a newer variety that has orange flowers that grow above leaves striped with burgundy, gold, yellow, pink, and green
Common Pests/ Diseases
Slugs, snails, and Japanese beetles delight in chewing holes in the leaves and flowers of cannas. The worst pest is a caterpillar known as the canna leaf-roller. The canna leaf-roller moth lays its eggs in the bud of the growing stalk, then the hatching caterpillars leave a sticky webbing that prevents the leaf from unfurling. Mild insecticides can help, or remove the leaf if you see that it's unable to unfurl.
Common diseases of canna lilies include:
- Rust fungus (remove and destroy affected leaves)
- Rhizome rot (dig up and destroy affected roots)
- Canna mosaic virus (remove and destroy entire affected plant)
- Aster yellows (another viral disease; remove and destroy affected plants)