Canna is one of several tropical garden plants that can be grown in northern climates with specialized care. The roots of cannas are technically rhizomes, but they are usually called bulbs because they look a lot like the roots of a normal plant bulb. Canna bulbs can be left in the ground over the winter in warm places (USDA hardiness zones 8 to 10), and the plants will come back every year as perennials. However, north of zone 8, the bulbs will die if they spend winter in the ground. In colder places, the plants are either thrown away at the end of the season like annuals, or the bulbs are dug up, stored for the winter, and then planted again in the spring.
Storing the bulbs is fairly quick and easy, depending on how many you have to dig up. However, they require some monitoring while theyre in storage.
Cannas are known for their beautiful, tropical-looking flowers that bloom all summer long. Their lush foliage and bright blooms add vibrant color to gardens, even during the hottest parts of summer when other flowers start to fade.
But what do you do with cannas when cold weather arrives? Can you dig up the bulbs (which are actually rhizomes) before the first frost, or is it better to leave them in the ground?
Why Dig Up Cannas Before Frost?
There are a few reasons you may want to dig up your canna rhizomes early
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Get a head start on spring planting. If you dig up the rhizomes in fall you can clean them up, divide them and store them over winter. This allows you to get them replanted as soon as possible in spring.
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Avoid damage from hard frosts, Extremely cold temperatures can damage rhizomes left in the ground Digging them up early guarantees they won’t get hit by an early deep freeze
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** Prevent rotting.** Wet soil and cooler fall temperatures can cause rhizomes to rot if left in the ground too long. Digging them up prevents rot issues.
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Make space for other plants. If you want to plant bulbs or cold weather crops in the same bed as your cannas, you’ll need to dig up the cannas first to make room.
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Propogate rhizomes. Digging up cannas in fall allows you to divide and propogate additional rhizomes. More rhizomes = more cannas for next year!
Reasons to Leave Cannas Until After Frost
While early digging has some benefits, there are also advantages to leaving cannas undisturbed until after the first frost:
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Let the foliage die back naturally. Frost kills back the foliage, making the plants look unsightly. But leaving them be allows the greens to die back naturally.
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Give rhizomes more time to store energy. Like other bulbs, cannas build up energy reserves in their rhizomes late in the season. Leaving them in place longer allows them to stockpile more energy for next year’s growth.
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Avoid shocking rhizomes. Digging cannas up early can stress and shock them. Letting them stay put avoids this shock.
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Use foliage as natural mulch. Once frost hits, the dead foliage provides natural insulation to the soil and rhizome below. This protective mulch layer helps regulate soil temperature.
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Delay spring planting prep. Leaving cannas in place longer pushes back the work of cleaning, dividing, and storing rhizomes until later. You can just relax and enjoy fall!
The Ideal Time to Dig Up Cannas
Most gardeners find a happy medium by digging cannas 2-4 weeks after the first light frost. A couple light frosts are enough to kill back the foliage and signal to the rhizomes it’s time to go dormant. But bulbs left in cool soil too long after this can rot.
Digging cannas during this 2-4 week post-frost window allows the foliage to naturally die back while still getting bulbs out of the ground before rot sets in. It prevents shock and damage from an early hard freeze. And it avoids the hassle of spring digging if you accidentally leave them in too long.
Here are some signs that cannas are ready for digging in that ideal 2-4 week window:
- Foliage has turned brown and limp after light frosts
- Stems feel rubbery and easily separate from rhizomes
- Soil is cool but not frozen solid
- Most other plants have already died back for winter
Digging Up Cannas: Step-By-Step
Digging up cannas properly ensures you get the healthiest rhizomes for storing over winter and replanting in spring:
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Wait for foliage to brown after light frosts. Don’t dig until frosts have done their job naturally killing back the foliage. This may take a few weeks after the first frost date.
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Use a garden fork to gently loosen soil and lift rhizomes. Try to avoid nicking or scratching rhizomes with tools. Damaged rhizomes often rot in storage.
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Carefully knock off excess soil. Gently shake or rinse rhizomes to remove soil but don’t damage the roots by scrubbing.
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Cut back foliage to 2-3 inches. Removing dead foliage prevents rotting during storage. But leave a stub to protect growth buds.
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Discard any mushy or rotten rhizomes. Healthy rhizomes feel firm. Toss any that are soft or smelly.
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Let rhizomes dry and cure for a week. Air curing toughens skins and prevents storage rot issues. Lay bulbs in a warm, dry spot out of direct sun.
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Wrap and pack for storage. Place cured rhizomes in newspaper, peat moss, or vermiculite. Store in a cool, dark spot around 45°F to 55°F.
Storing Cannas Over Winter
Proper storage conditions are key to successfully overwintering cannas. Aim for an environment that is:
- Cool (40°F – 55°F)
- Dark
- Dry with medium humidity
- Well-ventilated to prevent mold
Basements, unheated garages, and crawl spaces often provide suitable storage conditions. Make sure rhizomes are packed in dry peat moss or newspaper, not touching each other or packed too densely in boxes. Check them periodically over winter and discard any that show signs of rotting.
With proper storage care, most gardeners successfully overwinter 80% or more of their canna rhizomes.
Ready to Divide and Replant in Spring
Getting a jump on digging up cannas allows you to get rhizomes properly stored so they are ready for spring planting. In early spring, you can divide them to propogate additional bulbs. This ensures you’ll have plenty of vigorous cannas raring to go as soon as it’s warm enough to get them back in the ground.
While cannas can technically be left to overwinter in the ground depending on your climate, most gardeners have better success carefully digging and storing rhizomes. This guarantees cannas will survive winter and return even bigger and more floriferous next year.
When to Dig Up and Store Canna Bulbs
Canna bulbs should be dug up and stored for the winter in the fall, after the leaves have died back but before it gets really cold. Most gardeners dig up their bulbs as soon as the first light frosts kill the leaves in the fall or early winter. Light surface frost wont penetrate down to the buried bulbs, but a deep frost can ruin them.
Replant the bulbs in spring after the ground has fully thawed and all danger of frost has passed. This usually means late spring for most gardeners.
Many tropical plants that grow from bulbs, tubers, corms, or rhizomes can be dug up and stored in the same way that cannas are. These include elephant ears, blood lilies, caladiums, and dahlias.
What Is a Rhizome?
Rhizomes are plant stems that grow below the ground, not above the ground. Rhizomes do many things, like sending out new shoots and using nodes to send out roots into the ground for vegetative propagation, which is asexual reproduction. Most of the time, roots grow from the base of the rhizome and shoots grow from the top of the nodes. Rhizomes are very different from one plant to the next in terms of their thickness, size, and growth patterns, but they all do the same basic things.
How to Dig and Store Canna Lilly Bulbs | Rhizomes
When do you dig up Canna bulbs for winter storage?
Dig up canna bulbs for winter storage in the fall after the foliage has died back but before deep frost has arrived. Most gardeners dig up their bulbs immediately after the foliage has been killed by the first light frosts in fall or early winter. Light surface frost won’t penetrate down to the buried bulbs, but a deep frost can ruin them.
When should you dig a Canna plant?
Wait to dig the cannas up until after a frost has killed back the foliage. Once the foliage is dead, carefully dig around the canna bulbs. Remember that canna bulbs can multiply rapidly over the summer, so you will want to start digging a bit further out from where you originally planted the canna.
How do you get cannas to go dormant?
Dig clumps of cannas after the first frost. It is not necessary for cannas to be frosted prior to digging, but it is recommended. It serves as nature’s last signal for the bulbs (rhizomes) to go dormant. After digging the clumps of bulbs, remove soil by shaking or rinsing with water. Divide clumps into 3-5 eye bulbs (rhizomes).
Can Canna bulbs be left in the ground over winter?
In warm climates (USDA hardiness zones 8 to 10), canna bulbs can be left in the ground over winter, and the plants perform reliably as perennials, coming back year after year. However, north of zone 8, the bulbs will die if they spend winter in the ground.