Cannas (Canna spp.) are a genus of beautiful, easy-to-grow tropical and sub-tropical plants with showy flowers that come in red, pink, yellow, orange, and cream. Their flowers are very attractive to hummingbirds. Canna leaves are wide and long (resembling banana leaves) in green, bronze, or multicolored patterns. Most cannas grow up to 6 feet tall and occasionally as tall as 8 feet. These plants grow from rhizomes, modified stems that store nutrients and send up shoots.
Throughout their hardiness zone, cannas can remain in the ground as true perennials. In colder climates, the rhizomes must be dug in the fall and stored over the winter, then replanted in the spring. Best planted from rhizomes in the early spring, cannas can take a few weeks to sprout. After sprouting, they grow at a fairly quick pace and typically flower in their first year.
|Common Name||Canna, canna lily|
|Botanical Name||Canna spp.|
|Plant Type||Perennial, grown as an annual in colder zones|
|Mature Size||1 1/2–8 ft. tall, 1 1/2–6 ft. wide|
|Sun Exposure||Full sun|
|Soil Type||Rich, moist, well-draining|
|Soil pH||Acidic (6.0 to 6.5)|
|Flower Color||Red, orange, yellow, pink, cream, white; solid color or with contrasting spots|
|Hardiness Zones||7-10 (USDA)|
|Native Areas||South America, Central America, West Indies, Mexico, southeastern United States|
Watch Now: How to Grow and Care for Canna Lilies
In the garden, plant canna rhizomes horizontally in a planting hole 4 to 6 inches deep, fill the planting hole with soil and then add a thick layer of mulch. Space rhizomes 18 to 24 inches apart and don't bury them deeper than 2 to 3 inches, as planting them too deep will stunt the plant's growth. Cannas also don't like to be crowded, and if other plants encroach they might refuse to bloom. To prevent overcrowding, divide them every two to three years.
Canna leaves have a waxy coating that helps resist fungal diseases. They are also generally resistant to pest problems, although you might find caterpillars or grasshoppers eating the leaves—remove them by hand.
These plants prefer full sun to grow vibrant leaves and flowers, but they can survive in partial sun. Just make sure that the soil doesn't become overly moist.
Cannas can tolerate a variety of soils with proper drainage. They prefer rich soils that are high in organic matter. A soil pH of roughly 6.5 is ideal, but cannas can handle a wide range of acidic to neutral soils.
Water your canna once or twice a week. The soil should be kept uniformly moist but not soggy. Otherwise, this can lead to rot.
Temperature and Humidity
Cannas are sensitive to cold temperatures and frost, but they thrive in temperatures up to 90 degrees Fahrenheit. In areas that have relatively cool springtime temperatures, canna growth might start slowly.
In cooler climates, USDA zones 7 and lower, you can get a head start on the growing season by starting them indoors in pots and then move them outdoors once they are actively growing and all danger of frost has passed.
These plants are native to tropical zones, so they also do well in warm and humid conditions. If you live in a dry climate, you can raise the humidity around a container plant by placing it on a dish filled with water and pebbles, making sure the bottom of the pot isn't touching the water.
Cannas are heavy feeders. Feed monthly, or at least twice during the growing season, once in early spring, and again in mid-summer, with a fertilizer that is high in phosphorus, such as 5-10-5, to encourage blooming. You can also use plenty of compost or organic fertilizer to provide the plants with extra nutrients.
There are hundreds of canna cultivars, ranging in color and size. Some popular varieties include:
- 'King Humbert': an older variety with dark bronze-purple foliage and large red to orange-red flowers
- 'Shenandoah': bears deep pink flowers with burgundy leaves
- 'Tropicanna': produces orange flowers with leaves striped with burgundy, gold, yellow, pink, and green
- 'Pretoria' ('Bengal Tiger'): bicolored orange flowers and yellow and green striped foliage
- 'The President': very large scarlet flowers provide striking contrast with its deep green foliage
- 'Stuttgart': produces orange flowers and is distinguished by its bold striped green-and-white foliage
Cannas generally do not need pruning, but deadheading the flowers (once they have faded) will produce more blooms. If you prize the foliage of your cannas over their flowers, you can cut off the flower stalks before they bloom to enable the plants to direct their energy toward the foliage.
Cannas are readily propagated by digging up the rhizomes and dividing them for replanting. Do this early in the spring or in the fall.
- Carefully dig up the entire plant with a shovel, taking care not to damage the rhizomes or the roots of the mother plant.
- Trim the above-ground growth with sharp pruners so only about 1 inch extends from the crown (where the stems meet the rhizomes).
- Clean excess soil from the rhizomes and note where the old rhizomes meet the new. Cut along these joints to separate the rhizomes, making sure each piece has one or more eyes. If dividing in the fall, store them for the winter, then replant in the spring.
- Plant each rhizome division in prepared soil at a depth of 4 to 6 inches.
Potting and Repotting Cannas
Cannas are large plants, so bigger is better in terms of choosing an appropriate container. Choose a container that is no smaller than 16 inches in diameter with adequate drainage holes. A large container is not only important for aesthetic reasons of scale, A large container also gives the plant space to grow a strong and healthy root system, and prevents the container from becoming top heavy and tipping over as the plant matures.
Make sure the container has good drainage, and fill it with quality potting soil. Because cannas are heavy feeders, mix some slow-release fertilizer into your potting soil before you plant.
If you live in a cold-winter climate and have saved rhizomes from last year's plants, you can get a head start on the next growing season by potting up the rhizomes indoors four to six weeks before the last frost in spring. Maintain adequate moisture but do not make the soil overly wet. Move the pots outdoors or plant in the ground after the danger of frost has passed.
In colder climates, after the first frost in fall, cut the canna back to the ground. Carefully dig up the rhizome clumps and store them through the winter in peat moss, coconut coir, or vermiculite in a location where the temperature does not drop below 40 degrees Fahrenheit. Spray the rhizomes with water once in a while to prevent them from drying out, but don't allow the rhizomes to sit in a consistently damp medium.
You can bring container-grown plants indoors in their pots.
Common Pests & Plant Diseases
Slugs, snails, and Japanese beetles delight in chewing holes in canna leaves and flowers. But the worst pest is a caterpillar known as the canna leaf roller. The canna leaf roller moth lays its eggs in the bud of a growing stalk, and the hatching caterpillars leave a sticky webbing that prevents the leaf from unfurling. Remove a leaf if you see that it's unable to unfurl, and consider spraying the plant with insecticidal soap if pests are present
Cannas can have several other problems. They are susceptible to rust fungus, canna mosaic virus, and aster yellows. Observe foliage that appears sickly and discolored. With rust fungus, you often can simply remove the affected leaves. But with canna mosaic virus and aster yellows, you should dispose of the entire plant.
Can you split canna plants?
You can divide canna plants by splitting the rhizomes into sections and replanting them. Each section should have two to three "eyes" or growing points.
How often should I divide canna plants?
If you live in a warm climate where you can leave the rhizomes in the ground during the winter, divide them when they begin to become overcrowded. The timing depends on how well they grow in their location but a rule of thumb is every two to three years.
How do you keep cannas blooming?
Plant them in a sunny spot, fertilize them regularly starting in the spring. water them weekly if it does not rain, and deadhead the faded flowers.