All About Cannas
Nothing quite screams “island vacation” like a huge, healthy stand of canna lilies. While some varieties originate in the warmer climes, these giant herbaceous plants are also right at home in northern gardens.
Everyone, from zones 2 to 10, can grow cannas.
Canna Lilies: A Bit of Botany for Gardeners
While often referred to as bulbs, cannas actually sprout from rhizomes, which are underground stems. This isn’t just 'plant nerd' trivia. Understanding the way the plants grow will help when it comes time to dig and divide cannas. Cannas growing in suitable, in-ground conditions will spread via this rhizome, sometimes aggressively. Plants also produce seed, but it is much more common to acquire them as divisions of rhizomes. For all intents and purposes, you can treat cannas as bulbs, but dividing them is different.
You can’t really cut a true bulb in half, but you can cut a canna rhizome in half, as long as each resulting piece has an 'eye' (aka, a sprout - just like a potato!.
Cannas can stay in the ground during the winter in zones 7-10. In zones 6 through 2, you have to 'lift 'and store them if you want to keep plants from year to year.
Spring is the time to divide cannas (whether they’ve spent the winter in the ground or in your basement). Dig up (if applicable) the plant, or get it out of storage. Use a clean, sharp knife or a sharpened spade to chop the rhizome into pieces. Make sure that each piece has a node that will sprout into a new plant. This will look like a bud or a big bump.
Always divide cannas in the late spring or early summer so that they can grow and heal quickly. Letting freshly cut rhizomes sit in a dark basement all winter is a recipe for rot.
Canna Lilies: Tropical Look for Temperate Gardens
I think cannas lend a specific look and feel to a landscape—instant tropical oasis—and therefore aren’t necessarily the right plants for every garden. However, I have visited large botanical gardens like Chanticleer and The Biltmore Estate where cannas have been seamlessly integrated into mixed borders or gardens that I would describe as “English cottage style.” It seems that gardening acquaints strange bedfellows, sometimes.
To create a tropical oasis with cannas, combine with other sun-loving perennials, annuals, and shrubs that evoke island breezes.
Canna Lily Companions for Cold-Hardy (Zones 5-2)
- Hardy Banana
- Hardy hibiscus
- Cardinal flower
Annual or Tropical Companions for Canna Lilies. (Must be re-planted yearly or brought inside. Check zone indication at the time of purchase. Some are hardy in zones 6-7.)
- Bird of Paradise
- Elephant Ear
- Tropical hibiscus
Cannas, with their large, often multi-colored leaves, are useful in the landscape, even if you don’t want to create a Caribbean themed garden. I like to layer them into a border or flower bed, planting the rhizomes in the center or back of the bed and surrounding them with other plants of varying forms and textures.
Instead of planting cannas as a single big block, alternate them in the landscape bed along with a few other strategically placed larger plants. Dahlias and Helianthus maximiliani are both tall plants with finer textured leaves for some variety among the “giants.”
Daylilies, ornamental grasses, crocosmia, flowering tobacco, helenium, scabiosa, and verbena are all excellent medium and short companions for a more “traditional” look in the garden.
How to Grow Cannas in Containers
Varieties like Tropicanna, Tropicanna Gold, and Pretoria have variegated leaves that make for stunning “thrillers” or focal plants in container gardens. If you’d like a tropical taste without setting cannas loose in the garden, if your soil is dry and fast-draining, if you live in zone 6 or colder, containers are the way to go.
The only pictures you’ll see of big beautiful canna container gardens involve huge pots. Select a container that’s 18 to 24 inches in diameter (at a minimum) in which to grow cannas. Any smaller and you’ll be watering multiple times per day and the container will likely tip over in a stiff wind.
If you’ve ever had any training in floral design, you’ll have learned about the rule of thirds. The container should be 1/3 of the height of the arrangement for the composition to look proportional.
- Fill a large pot with lightweight soil, and plant rhizomes 2-3 inches below the soil level.
- Leave at least 2 inches between the top of the soil and the edge of the container so that the water doesn’t run over the side of the container.
- Abide by the same advice for landscape plantings, and layer with some plants of varying heights—ornamental grasses, coleus, crocosmia are all good options. Anything that softens the bottom of the canna plant will do!
As plants grow you’ll find yourself needing to water up to once per day. You can also set the container in a tray filled with water to avoid an afternoon slump.
If you're unable to meet your Canna Lilies' watering needs, you can expect smaller plants with smaller leaves.
Overwintering Cannas Where It’s Cold
In zones 6-2 you’ll need to dig up canna rhizomes and bring them inside for the winter. Alternatively, if you have grown them in pots, you can bring the pots into a garage or basement.
When a hard frost knocks the foliage back it’s time to get out the pruning shears. Cut back all of the foliage. Dig up in-ground plants and shake the soil off. You can also hose them off and let the rhizomes dry outside under cover for a few days. Carefully remove all but about an inch of whatever stem is left. Bring pots and rhizomes inside to store. Layer rhizomes between sheets of newspaper and store in a cool (45-50 degree), dry space. Keep plants in pots dry until you move them outside for the summer. Plants can be replanted outside or moved outside when nighttime temperatures are consistently above 50 degrees.
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About the Author: Katie is a writer, runner, and reader, living in southern coastal North Carolina. Her favorite garden is her "wild flower patch" where something new is always blooming (or taking over).Back to top.