Canna lilies are stunning tropical-looking plants that produce beautiful flowers in shades of red, orange, yellow and pink. Their large, banana-like leaves and height make them stand out in any garden. While cannas are not cold hardy, there are some tricks to help them survive winters in cooler climates.
An Overview of Canna Lilies
Cannas are herbaceous perennials that grow from rhizomes, which are underground storage organs. The rhizomes store food reserves that allow the plants to survive through winter and fuel growth in spring. Cannas thrive in hot, humid environments and prefer rich, moist soil. They grow best in full sun exposure.
There are many cultivars of canna lilies with heights ranging from 1-8 feet tall. The flowers come in various colors and bloom throughout summer. The foliage is also attractive, with wide, tropical-looking leaves. Cannas spread rapidly by rhizomes, making them great for mass plantings.
Hardiness and Winter Care
Cannas are only hardy in USDA zones 8-10, where winters stay above 10°F. In zones 8-10, the rhizomes can be left in the ground over winter. Just cut back the foliage after it is killed by frost. Then mulch the rhizomes with a thick layer of bark mulch or straw to insulate them from cold weather.
In cooler climates, canna rhizomes won’t survive winter if left in the ground. They need to be dug up in fall and stored indoors until spring. When digging them up, cut off the foliage and allow the soil to dry from the rhizomes before storage. Healthy rhizomes are firm and show pink bud patches that will produce new shoots.
Storing Rhizomes for Winter
Canna rhizomes can be overwintered in a few different ways
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Leave in pots Put the rhizomes in pots filled with peat moss vermiculite bark chips or sand. Keep them in a cool garage or basement where temps stay above freezing.
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Pack in dry material: Place rhizomes in boxes of dry vermiculite, peat moss, wood shavings or perlite. Store in a cool, dry spot around 40-50°F.
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Bury underground: In zones 6-7, cannas can be overwintered like dahlias by burying the pots or rhizomes in trenches 1-2 feet deep. Cover with soil, leaves or straw.
Check stored rhizomes every few weeks and remove any that show signs of rotting. Replant the rhizomes in spring after the last frost when soil temperatures reach 65°F.
Growing Tips to Overwinter Cannas
Here are some tips to help cannas survive winter in pots or in the ground:
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Plant in spring: Start cannas after the last spring frost when soil warms. This gives more time to establish before winter.
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Provide rich soil: Amend soil with compost or manure to encourage rhizome growth.
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Give plenty of sun: At least 6 hours of direct sun per day keeps cannas blooming into fall.
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Water deeply: Give cannas 1-2 inches of water per week. Too little water causes foliage dieback.
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Stake tall varieties: Staking prevents toppling of top-heavy, giant varieties.
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Mulch heavily: Apply a deep, 6-8 inch layer of mulch over rhizomes left in the ground.
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Divide frequently: This prevents overcrowding and encourages vigor. Divide every 2-3 years.
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Remove dead foliage: Cut back spent leaves and stems to prevent disease issues.
The Best Canna Varieties for Overwintering
Some cannas are better choices if you want to overwinter them in pots or in the ground. Look for these winter-hardy varieties:
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Canna ‘Pretoria’ – One of the most cold tolerant. Overwinters in ground down to zone 7.
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Canna ‘Stuttgart’ – A dwarf variety, under 3 feet. Easier to dig rhizomes.
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Canna ‘Ra’ – Grows just 2-3 feet tall. Produces purple-red leaves.
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Canna ‘Intrigue’ – A new hybrid bred to be cold hardy and rebloom.
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Canna ‘Australia’ – Versatile variety that tolerates wet soil well.
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Canna ‘Crimson King’ – Cold hardy and makes a dramatic statement.
Risks of Leaving Cannas in the Ground
In areas colder than zone 8, leaving cannas in the ground over winter comes with some risks:
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Rhizomes may rot if soil stays wet, especially with heavy mulch.
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Rapid temperature drops below 10°F can damage rhizomes.
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Repeated freezing and thawing of soil heaves rhizomes out of ground.
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Lack of insulating snow cover exposes rhizomes to cold damage.
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Rodents and critters may feed on rhizomes left in the ground.
Even in warm zones, cold-sensitive varieties may need some winter protection if temps drop below 15°F for an extended time. Check with local nurseries to see if overwintering cannas in the ground is possible in your specific area.
Overwinter with Care
With some advance planning and proper care, you can overwinter cannas and enjoy these exotic-looking plants for years to come. By providing rich soil, ample moisture and lots of sun exposure during the growing season, the rhizomes will be strong and healthy when going dormant for winter.
Storing the rhizomes properly and protecting in-ground plantings will give cannas the best chance of surviving cold winters. With a little luck from Mother Nature, your cannas will return vigorously the following spring.
Growing on canna rhizomes
There are two basic methods to restart your canna plants.
1. Pot up the rhizomes, individually or several to a pot, in some form of multi-purpose compost. Water them in and let nature take its course. When the canna feel ready they will begin to grow. This will happen fairly soon if you are starting them off indoors. In a frost free greenhouse, when they start growing will depend a lot on the general weather conditions. They should get going some time in March.
2. Force them. This involves exactly the same initial process as above. Fill a pot half full with some form of multi purpose compost. Place your rhizome horizontally on the compost and then cover the rhizome with more compost. Water the pots and allow them to drain. Cover the pots with cling film. The pots are then put in either a heated propagator or, my personal favorite, heated mats. This is done instead of just leaving them alone.
What are the advantages of using heat. The main one is it allows you more control over the plants. With heat mats, you can set up a bit more of a production line if you have a garden full of Canna, gingers, dahlias, or anything else you need to get going in the spring. Once a cannabis plant pot is put on a heat mat, it will only be a matter of days before new shoots appear on top. For example in this shot:
Thanks to the magic of microchips, I can tell you that this picture was taken on March 12th and that these plants were put on the heat mat on March 2nd. For the next wave, the plants can be taken off the mats once they are big enough. Now all that is needed is a vigilant eye for aphids and the odd wayward slug. (And water of course).
Can lilies be left in the ground over winter?
FAQ
How do you winterize canna lilies in the ground?
How cold can canna lilies tolerate?
Do you have to dig up canna lilies in the fall?
Do canna lilies come back every year?
Can you leave canna lilies in the ground over winter?
You can leave canna lilies in the ground over winter if the soil does’t freeze where you live. If you are in zone 7 or lower, then it’s too cold for them to survive outdoors. How long can you store canna bulbs?
How do you overwinter canna lilies?
By far the most popular method of overwintering canna lilies is to dig up and store the bulbs. This is a must if they are planted in the garden. The nice thing about it is that there’s no rush to dig them up. You can leave them in the ground even after a hard freeze kills the plant.
When should I cut down canna lilies?
You need to cut down your Cannas in the fall just before the winter hits. Ideally, you need to cut the roots and stems of Cannas. Do this once the first frost hits your region. Let the plant lose all its leaves, prepare the rhizomes for the winter. Can you overwinter Canna lilies indoors? Yes, you can overwinter your Canna lilies indoors.
Are Canna lilies good for winter?
Canna lilies are gorgeous tropical plants that wow in the garden. If you live in a cooler climate, you probably want to store your canna bulbs for the winter. Here are some tips to get your cannas through the cold weather to bloom again next year. Canna lilies are such a joy in the garden.