Canna lilies are stunning tropical-like plants that produce beautiful blooms in a range of dazzling colors. Their exotic flowers and large, lush leaves make them a summertime showstopper in any garden.
However, in colder climates, gardeners face a dilemma when winter approaches – should I leave my canna lilies in the ground or dig them up?
This is a common question for those growing cannas in areas that experience freezing winter temperatures. The answer depends on several factors, which we’ll examine in this article.
An Overview of Canna Lily Winter Hardiness
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Canna lilies are native to tropical and subtropical regions, so they are not naturally cold hardy. They can be damaged and even killed by frigid winter conditions.
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The rhizomes are the most vulnerable part of the plant They can rot and decay if exposed to sustained freezing and repeated freeze-thaw cycles.
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Canna lilies are typically hardy only in USDA zones 8-11. In zones 3-7 they are grown as annuals or dug up for overwintering.
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Certain varieties have been bred to be more cold tolerant than others. But even hardy cannas need protection where winters get severely cold.
Key Considerations for Leaving Cannas In the Ground
There are a few key factors to weigh when deciding whether to leave your canna lilies in the ground over winter:
1. Your Climate and Hardiness Zone
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In zones 8-11, cannas can potentially survive winter in the ground. But additional protection like mulching may be needed even here.
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In zones 3-7, leaving cannas in the ground over winter is risky and often fatal to the plants. Digging them up is recommended.
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Pay attention to your specific microclimate – sheltered spots near buildings or walls may offer a bit more warmth.
2. The Canna Variety
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Some cannas are bred to be more cold tolerant, such as Canna ‘Phasion’, ‘Tropicanna’, and ‘Australia’. Check your variety’s hardiness rating.
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Dwarf cannas are generally less hardy than full-size varieties.
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If you don’t know the variety, assume it’s not winter hardy and dig it up.
3. Site Selection and Prep
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Cannas left in the ground should be planted in a spot protected from wind and with excellent drainage.
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Adding a thick layer of mulch around the plants helps insulate the roots. Leaves or straw work well.
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Cut back the stalks and foliage to reduce freezing damage.
Overwintering Cannas by Digging Up the Rhizomes
In climates with harsh winters, digging up and storing the rhizomes is recommended:
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Wait until after the first frost blackens the foliage, then carefully dig up the rhizome clumps.
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Shake off excess soil and remove the dead stalks and leaves.
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Allow the rhizomes to dry and cure for 1-2 weeks in a warm, dry spot.
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Pack cured rhizomes in peat moss, vermiculite, or perlite and store them in a cool basement or garage.
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Check periodically for rotting and discard any diseased rhizomes. Replant the healthy ones in spring.
Providing Winter Protection for In-Ground Cannas
If you decide to leave cannas in the ground, take these additional steps:
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Mulch heavily around the plants, at least 6 inches deep, after the first frost.
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Wrap or cover the rhizomes with insulation like bubble wrap to prevent frost penetration.
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Bucket or pot method – Place a bucket or pot over each rhizome and fill with leaves/straw.
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Erect a cold frame or hoops around the bed and cover with plastic sheeting.
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Wrap or cover overwintering cannas with frost blankets once temperatures drop below freezing.
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Check for frost heave and re-cover any exposed rhizomes.
Spring Care for Overwintered Cannas
As spring arrives, uncover cannas and remove protective mulch and coverings. Here are some tips for spring care:
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Water lightly to help break dormancy. Avoid overwatering initially.
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Apply balanced fertilizer once new shoots appear.
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Cut back any frost damaged or dead foliage. Healthy green leaves will soon replace it.
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Transplant cannas to a new location if needed. Divide large rhizome clumps.
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Be prepared to cover plants if any late frosts threaten.
The Verdict: Can Cannas Stay In the Ground Over Winter?
In zones 8-11, cannas may survive winter in the ground if given adequate protection from cold. Heavy mulching and insulating the rhizomes are musts.
In zones 3-7, leaving cannas in the ground over winter is risky and will likely kill the plants. Digging up and storing the rhizomes indoors is the best way to overwinter them.
While not cold hardy by nature, with proper care cannas can successfully make it through winter in suitable climates. In marginal zones, be prepared to lose a few plants as you determine what works best in your conditions. Proper site selection, winter prep, and protective coverings can help maximize their survival.
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. Then rather than just letting them get on with it, the pots are placed either in a heated propagator, or my preference – heated mats.
What are the advantages of using heat. The main one is it allows you more control over the plants. If you have a garden full of Canna, gingers, dahlias or what ever you need to get going in spring, the use of heat mats allows a bit more of a production line to be set up. Once a canna pot is placed on a heat mat it is just a question of days before new shots are poking through the surface. For example in this shot:
Thanks to the miracle of the micro chip I can tell you that this picture was taken on 12th March and my camera tells me these plants were placed on the heat mat on the 2nd March. Once the plants are growing they can be taken off the mats to make way for the next wave. 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?
Cannas are quite tender and you should dig and store the roots after the foliage withers and dies back. Shake the excess soil off the roots and store them in dry sand, peat moss or sawdust. The roots will be dormant and won’t require water, but should be protected from complete desiccation.
Do canna lilies come back every year?
CANNA LILIES. The perennial that attracts hummingbirds and comes back year after year !!
Do canna lilies have to be dug up for winter?
Although technically they are not bulbs, but rhizomes, cannas need to be treated as tender bulbs and must be dug up to survive the winter.
Can you leave cannas in pots over winter in winter?
… you can either store the roots, container and all, or remove the clump from the container and proceed in the same way as with garden-grown Cannas, depending …