I consider myself an equal-opportunity gardener in the sense that I like to grow a variety of different plants in my garden and home landscape. Like most gardeners, I appreciate the ecological value in having a wide diversity of flowering plants, and I get joy from a variety of different colors and types of flowers, foliage, and plant-growth habits.
One flowering plant that had been missing from my landscape until the past couple of summers is the stately canna. These tall tropical-looking plants with banana-like paddle shaped leaves that wrap in orderly ruffles around the stems, have become the focal point in several different plantings in my landscape.
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Looking at the flashy and flamboyant red, orange, yellow and pink flowers of these plants, I now wonder how I ever lived my summers without these spectacular specimens.
Focal point of any planting
Cannas can be used in many garden and landscape settings as both focal points and attractive accents. Cannas are tall plants, with most varieties reaching 4 to 6 feet in height. Some monster varieties can reach up to 8 feet tall! Because of their height, cannas can bring structure as a tall border; as a backdrop in a flower, perennial, or even shrub bed; or soften the height of structures and raised decks in the landscape. There are also smaller dwarf varieties of cannas.
If you have a water feature in your garden or landscape, try adding a canna or two for an instant tropical touch. Cannas also serve as spectacular vertical or “thriller” plants when used in containers along with other flowers which have creeping, mounding, or spreading growth habits.
While the flowers are the focal point of canna plants, a wide variety of foliage colors and patterns exist, adding visual interest to the plant. Many varieties feature variegated foliage with streaks of yellow, red, orange and cream colors highlighting the over-sized leaves.
Some pollinators are attracted to canna flowers, and in my landscape, hummingbirds seem to prefer cannas over other flowers that they have typically visited.
They’re not true bulbs
Cannas are commonly referred to as summer-flowering bulbs, although technically they are not bulbs. These plants multiply beneath the soil from a rhizome, which is an underground stem that grows horizontally. Cannas are tropical plants and as such, require a fair amount of full sun, preferably a minimum of 6 hours of direct sun each day. The plants will tolerate some shade and do well in locations with a lot of filtered or dappled sunlight in the afternoon and evening hours.
Cannas require fertile, moist soil, so if your soil is not high in organic matter, loosen the soil to 12- to 14-inches-deep and add some compost or peat moss to the planting hole. Cannas do not tolerate cold soil temperatures, so these are not the first items I plant each spring. They are actually the last flowering plants that I plant, and never before Memorial Day. I planted the last of my transplants this past week, and still have a few in pots in need of a home!
While canna bulbs are available for purchase at some garden centers each spring, many more garden centers offer these plants as transplants growing in pots, which at this point of the growing season is the best method for planting cannas.
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Caring for cannas
Cannas do best in moist soil and require a large amount of supplemental irrigation for full flowering, especially during the hottest and driest times of the summer. A layer of mulch helps to retain soil moisture. A complete fertilizer such as 10-10-10 or 5-10-5 applied two or three times throughout the growing season will result in continued flower development well into the fall months.
As flowers fade, carefully deadhead spent and browning flowers, taking care not to remove additional flowers located immediately below spent flowers. After deadheading a stem several times and with no additional flowers forthcoming on the stem, cut that stem back to the leaves. Each plant will produce several additional stems throughout the growing season.
Cannas are not prone to disease unless they are planted in dense stands in very wet conditions, and are rarely harmed by insects, although some insects may feed on the large leaves.
Digging cannas for winter
Canna rhizomes must be dug in the fall and stored each winter indoors. Cannas planted in containers can simply be moved into a garage or basement for the winter. While the task of digging the rhizomes can seem like a chore (it actually kept me from planting them for years), the reward is that the rhizomes greatly increase in size during the growing season and can be broken into several different rhizomes, each of which can be planted next spring, greatly increasing your canna holdings!
When digging the rhizomes, carefully remove all soil and then lay them out to dry in a shed, garage or basement for a few weeks. Once dry, the rhizomes can be stored in containers indoors with some peat moss or shredded newspaper sprinkled between the rhizomes.
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In the spring, rhizomes can be planted directly in the ground once the soil temperature reaches 65 degrees Fahrenheit or they can be started indoors in pots in late winter and then transplanted outdoors.
The original three cannas I planted three years ago turned into a dozen plants last summer, which yielded three dozen plants this spring!
Mike Hogan is an associate professor at Ohio State University and an educator at the OSU Extension.