Cannas are bold, tropical-looking plants grown for their attractive flowers and foliage. Flower colors include yellow, orange, pink, and red. The large, banana-like foliage may be green, bronze, or burgundy. The foliage of some cultivars is striped or marbled in various colors. Most canna cultivars grow to a height of 3 to 5 feet. However, there are dwarf cultivars that grow only 1.5 to 2 feet tall. A few "giants" may reach a height of 8 to 10 feet. Cannas can be used as temporary screens, accents in beds, or as background plantings in borders. The smaller cultivars perform well in large containers.
Cannas are normally grown from rhizomes. However, it is possible to grow cannas from seeds.
Sow canna seeds indoors in mid- to late February in a commercial germination medium, such as Jiffy Mix. Prior to sowing, soak the seeds in water for 12 to 24 hours to soften their seed coats and improve germination. After sowing, lightly cover the seeds, then water the medium. Allow the medium to drain for a few minutes. Afterwards, cover the container with clear plastic wrap and place it in a warm location. The temperature of the medium should be maintained at 70 to 75 degrees Fahrenheit. Germination should occur in 7 to 14 days. When the seeds germinate, remove the plastic wrap and place the seedlings in a sunny window or under fluorescent lights. When the canna seedlings are large enough to handle, transplant them into individual containers. Continue to grow the seedlings in a sunny window or under fluorescent lights. Harden the plants outdoors for 7 to 10 days before planting them in the landscape. Initially place the cannas in a shady, protected location. Then gradually expose the plants to longer periods of sunlight. Plant the cannas outdoors when the danger of frost is past (mid-May in central Iowa). Available seed-grown cannas include those in the Tropical and South Pacific Series.
Canna rhizomes can be planted directly outdoors after the danger of frost is past or started indoors in large pots in March. The rhizomes should be planted 4 to 5 inches deep.
Cannas perform best in moist, well-drained soils in full sun. (The planting site should receive at least 6 hours of direct sunlight.) Water plants once a week during dry weather. To promote growth, fertilize in spring and mid-summer with a balanced garden fertilizer, such as 10-10-10. Remove spent flowers to maintain their attractive appearance and promote additional blooms.
Several viruses, such as canna yellow mottle virus and bean yellow mosaic virus, have become serious diseases of cannas in the last several years. Possible symptoms include mottling or streaking of foliage, stunting of plants, and poor flowering. Virus-infected cannas cannot be cured. Plants that exhibit virus-type symptoms should be dug up and destroyed. Because of virus problems, home gardeners should purchase cannas only from reputable garden centers/nurseries that sell virus-free plant material.
Gardeners can choose from numerous canna cultivars. A sampling of some of the more popular cultivars is listed below.
'Aida' - soft pink flowers, dark green leaves, 3 to 3.5 feet tall.
'City of Portland' - coral pink blossoms, green foliage, 3.5 to 4 feet tall.
'Crimson Beauty' - rose-red flowers, green foliage, 3 to 4 feet tall.
'Lucifer' - red flowers with yellow borders, green leaves, 2 feet tall.
'Miss Oklahoma' - watermelon pink blossoms, green foliage, 3 feet tall.
'Richard Wallace' - golden yellow flowers, green leaves, 4 feet tall.
'Rosamond Cole' - orange-red flowers with yellow edges, dark green foliage, 3 feet tall.
'The President' - scarlet blossoms, green leaves, 3 to 3.5 feet tall.
'Black Knight' - crimson red flowers, burgundy leaves, 3 to 3.5 feet tall.
'Red Futurity' - dark red flowers, burgundy foliage, 3 to 3.5 feet tall.
'Wyoming' - orange flowers, bronze-red foliage, 3 to 4 feet tall.
'Cleopatra' - yellow flowers with red spots, dark green foliage with bronze-red markings, 3 to 4 feet tall.
'Inferno' - orange-red flowers, foliage striped with green, yellow, orange, and pink, 3 to 4 feet tall.
'Intrigue' - light salmon flowers, green and burgundy lance-leafed foliage, 8 to 10 feet tall.
'Pretoria' ('Bengal Tiger') - orange flowers, yellow and green striped foliage, 4 to 6 feet tall.
'Striped Beauty' - yellow flowers with white markings, green foliage with creamy yellow stripes, 3 feet tall.
'Stuttgart' - orange flowers, green and white variegated foliage, 3 to 4 feet tall.
Tropical Series - Cultivars in the Tropical Series include 'Tropical Rose,' 'Tropical Red,' 'Tropical Salmon,' 'Tropical Bronze Scarlet,' 'Tropical White,' and 'Tropical Yellow.' Plants grow 2 to 3 feet tall. All have green foliage with the exception of 'Tropical Bronze Scarlet.' 'Tropical Bronze Scarlet' has scarlet red flowers and bronze foliage.
South Pacific Series - 'South Pacific Scarlet' is a 2013 All-America Selection and currently the only cultivar available. Plants grow 3 to 4 feet tall, have green foliage, and produce scarlet red flowers.
In Iowa, cannas will not survive the winter outdoors. Canna rhizomes must be dug in the fall and stored indoors over winter. Cut back plants to within 4 to 6 inches of the ground a few days after a hard, killing frost. Then carefully dig up the canna clumps with a spade or fork. Leave a small amount of soil around the cannas. Allow them to dry for several hours. Afterwards, place the cannas in large boxes, wire crates, or in mesh bags. Store the cannas in a cool (40 to 50 degree Fahrenheit), dry location. Large clumps can be divided next spring before planting. Each section (division) should have at least 3 to 5 buds.
Links to this article are strongly encouraged, and this article may be republished without further permission if published as written and if credit is given to the author, Horticulture and Home Pest News, and Iowa State University Extension and Outreach. If this article is to be used in any other manner, permission from the author is required. This article was originally published on January 16, 2015. The information contained within may not be the most current and accurate depending on when it is accessed.