Canna lilies (also called cannas) are beautiful and very easy to grow, but they're not for the faint of heart. They are generally huge with large showy flowers, and when you grow them, you are making a visual statement with an exclamation mark. The leaves are quite colorful, ranging in color from green, cream, red, and yellow and they are capped off with a large showy flower. Cannas work well in pots and can be transplanted indoors or outdoors, using the plants' own rhizomes (underground roots). The rhizomes can also be stored indoors for winter.
- Botanical Name: Canna indica
- Common Name: Canna lilies, Cannas, Indian shot, African arrowroot, Edible canna, Purple arrowroot, Sierra Leone arrowroot
- Plant Type: Rhizomatous perennial
- Mature Size: Each plant can grow 4 to 6 feet tall; they need a 20 to 24-inch diameter around each hand-size rhizome.
- Sun Exposure: Full sun
- Soil Type: Rich, water-retentive, well-draining soil
- Soil pH: 6.5
- Bloom Time: Early summer
- Flower Color: Range from yellow to orange to almost black and neon pink
- Hardiness Zones: 8 through 12
- Native Areas: South America, Central America, West Indies, Mexico, and the Southeastern United States
How to Grow Cannas
Cannas are easy to plant. If you live in a climate that is zone 7 or warmer, you can grow cannas outside year-round. If you live in a cooler climate, you can either grow them inside in pots or you can plant them outside during the warm months and when winter hits, cut off the plants' rhizomes and bring them inside, where you can replant them in pots or store them for winter. To store the rhizome over the winter, shake off the soil and keep them in a damp medium in a cool (frost-free), dry place.
Canna leaves are wide and long, can have a wild stripe pattern, and their colors can range from yellow to orange to almost black and neon pink. Watching canna leaves shoot up and then unfurl over a few days is an impressive sight. Most will grow up to 6 feet tall. They are good-humored plants, not demanding much care.
While it is possible to buy plants that are already growing, it is common to grow cannas from the rhizomes. To plant the rhizomes, place them 4 inches below the surface of the potting soil, making sure there are no air pockets and that they are surrounded by soil. If you live in a cold climate (less than zone 7), you can start your cannas inside and move them outside once the overnight temperatures are consistently above 50 degrees Fahrenheit.
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.
The soil should be saturated, but well-draining, otherwise the rhizome may rot. In drier climates, water 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 degrees Fahrenheit. Humid environments are not beneficial.
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.
Potting and Repotting
Cannas are large plants, so bigger is better. 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.
Varieties of Cannas
There are hundreds of varieties of cannas, ranging in color and size. Some include:
- "King Humbert" originated in 1902 and has dark, bronze-purple foliage and red flowers.
- The "Shenandoah" variety bears deep pink flowers over burgundy leaves.
- "Tropicana," is a newer variety that has orange flowers that grow above leaves striped with burgundy, gold, yellow, pink, and green.
Pruning is not necessary. If your Canna lily plant is looking tired or ragged, you can cut the plant down to the ground, add some fertilizer and water, and the plant will quickly recover. You can even do this mid-summer with success.
Pests and Diseases
Slugs, snails, and Japanese beetles are all pests of this plant which chew holes in the leaves and eat the flowers. The worst pest is the caterpillar, known as the canna leaf-roller. The canna leaf-roller moth lays its eggs in the bud of the growing stalk and then the hatching caterpillars leave a sticky webbing that prevents the leaf from unfurling, thus protecting the pest. Mild insecticides can help or remove the leaf is you see it's unable to unfurl.