Introduction
Few plants bring as much drama and tropical flair to a summer garden as cannas. Their bold, paddle-shaped leaves and vibrant blooms make them a favorite for adding height and color to borders and containers. While these plants look like they belong in a rainforest, they are surprisingly easy to grow across most of the United States. At Longfield Gardens, we love how cannas bridge the gap between late summer and the first hints of autumn with their tireless energy.
If you live in a region where winters are cold, you likely know that these tropical beauties need a little help to survive the freezing months. The most common question we hear as the season winds down is exactly when to move them from the garden to safety. This guide will help you identify the perfect window for lifting your canna rhizomes, how to prepare them for storage, and how to ensure they stay healthy until spring.
By following a few simple steps, you can enjoy the same beautiful plants year after year. Understanding the signals your plants and the weather are giving you is the secret to a successful harvest.
The Best Time to Dig Up Canna Bulbs
The short answer to when you should dig up your canna rhizomes—often called "bulbs"—is right after the first light frost of the autumn. While it might be tempting to tidy up the garden as soon as the weather turns chilly, waiting for that first frost is actually a gift to the plant.
Cannas are sun-loving plants that spend the entire summer photosynthesizing and storing energy. This energy is sent down into the underground rhizomes, which act like a battery for next year’s growth. If you dig them up too early while the leaves are still lush and green, you are cutting off that energy supply prematurely.
When the first light frost hits, you will notice the foliage starts to wilt, turn brown, or even turn black. This is the plant's natural signal that it is time to go dormant. Once the top growth has been "zapped" by the cold, the plant stops producing energy and prepares for its winter rest. This is your cue to get your shovel ready.
Why the First Frost Matters
The first frost serves as a clear boundary. It tells the plant that the growing season is officially over. Digging after this point ensures the rhizomes are as plump and nutrient-rich as possible. However, you do not want to wait too long. While the leaves can handle a light frost, the rhizomes themselves should not be allowed to freeze. If the ground freezes solid, it can damage the cellular structure of the rhizome, leading to rot or death.
Watching the Weather Forecast
Because autumn weather can be unpredictable, it is helpful to keep an eye on your local forecast starting in late September or October. A "light frost" usually occurs when temperatures dip just below 32°F for a few hours at night. If a "hard freeze" (temperatures below 28°F for an extended period) is predicted and you haven't had a light frost yet, it is better to dig them up a day or two early rather than risk losing them to the deep cold.
Key Takeaway: Wait for the first light frost to blacken the leaves before digging. This allows the plant to store maximum energy for next year's blooms.
Knowing Your USDA Hardiness Zone
Whether or not you need to dig up your cannas depends entirely on where you live. At Longfield Gardens, we use USDA Hardiness Zones to help gardeners determine if a plant can survive the winter in the ground. Cannas are generally considered hardy in zones 8 through 11. In these warmer climates, the ground rarely freezes deep enough to reach the rhizomes, and the plants can remain in the soil year-round.
Zones 8 to 11 (The "Stay in the Ground" Zones)
If you live in the South or along the West Coast, you can usually leave your cannas exactly where they are. Once the foliage dies back in the winter, simply cut it down to the ground. You may want to add a light layer of mulch to keep the area looking tidy, but the rhizomes will stay safe underground and sprout again when the soil warms in the spring.
Zone 7 (The "Transition" Zone)
Gardeners in zone 7 are in a unique position. In many years, cannas will survive the winter here if they are given a thick layer of mulch—about 4 to 6 inches of straw, shredded leaves, or wood chips. This acts as a blanket, keeping the soil temperature stable. However, if a particularly harsh winter arrives, the rhizomes may still struggle. Many zone 7 gardeners choose to dig up their favorite or more expensive varieties just to be safe.
Zones 3 to 6 (The "Must Dig" Zones)
In these northern and central regions, the ground freezes deep and stays frozen for months. Cannas will not survive these conditions outdoors. For gardeners in these zones, lifting and storing rhizomes is a standard part of the autumn garden routine. While it takes a little extra effort, it is a rewarding way to preserve your investment and grow massive, impressive clumps over several seasons.
How to Dig Up Canna Rhizomes Step-by-Step
Once the frost has touched your plants, it is time to get to work. You don't need a lot of fancy equipment—a simple garden spade or a digging fork will do the trick. The goal is to lift the rhizomes without causing unnecessary damage.
1. Cut Back the Foliage
Before you start digging, use a pair of garden shears or a sharp knife to cut the stalks down. You want to leave about 2 to 4 inches of stem protruding from the ground. This gives you a "handle" to grab and helps you keep track of where the center of the clump is located. Removing the bulk of the messy, frosted leaves makes the rest of the job much easier.
2. Loosen the Soil
Canna rhizomes can grow surprisingly large over a single summer. Instead of digging straight down next to the stem, start about 6 to 10 inches away from the base of the plant. Push your spade deep into the soil and gently pry upward. Work your way all the way around the plant in a circle. This ensures that you don't accidentally slice through the fleshy rhizomes.
3. Lift the Clump
Once the soil is loosened, use your digging fork or spade to lift the entire clump out of the ground. Don't be surprised if the clump is heavy! A healthy canna can produce a massive root system in a few months. Gently shake the clump to remove large chunks of soil. You can use your hands to brush away more dirt, but there is no need to get them perfectly clean just yet.
4. Inspect the Rhizomes
While you have the plants out of the ground, take a quick look at their health. You want rhizomes that feel firm and heavy for their size. If you see any sections that are mushy, slimy, or clearly damaged by insects, you can snap those off and discard them. Healthy rhizomes are usually a creamy white, tan, or pinkish color depending on the variety.
What to do next:
- Cut stalks to 3 inches.
- Dig a wide circle around the plant.
- Lift the clump gently to avoid bruising.
- Shake off loose excess soil.
Cleaning and Curing for Storage
Once the rhizomes are out of the ground, they need a short period of "curing" before they go into long-term storage. Curing is simply a fancy word for letting the outer skin dry and toughen up. This helps prevent rot and protects the plant from drying out too fast during the winter.
To Wash or Not to Wash?
There are two schools of thought on cleaning cannas. Some gardeners prefer to wash all the soil off with a garden hose so they can clearly see the "eyes" (growth points) of the rhizomes. Others prefer to leave a little soil on to provide a natural protective buffer.
If your soil is heavy clay, washing them is usually a good idea because clay can hold too much moisture and lead to rot. If you have sandy soil, a simple shake is usually enough. If you do choose to wash them, make sure they dry completely afterward.
The Curing Process
Move your lifted rhizomes to a dry, frost-free location like a garage, shed, or covered porch. Spread them out in a single layer on a piece of cardboard or a newspaper. Let them sit for several days—usually 3 to 7 days is plenty. During this time, the cut ends of the stems will dry out and the outer skin of the rhizomes will become less fragile.
Avoid curing them in direct sunlight, as this can cause them to overheat or dry out too much. A cool, shaded spot with good air circulation is ideal.
Dividing Canna Rhizomes
One of the best things about cannas is how much they multiply. A single rhizome planted in May can easily become a clump of five or ten by October. You can divide these clumps either in the fall after digging or in the spring before replanting.
Many gardeners find it easier to divide in the fall because the rhizomes are already out and the "eyes" are often easier to see. To divide them, simply pull the rhizomes apart with your hands or use a clean, sharp knife. Each division should have at least one or two "eyes"—the small, rounded bumps where new stems will emerge.
If you use a knife, it is a good idea to let the cut pieces dry for an extra day before packing them away. This allows the "wound" to callous over, which acts as a barrier against disease.
Proper Winter Storage Conditions
The key to keeping cannas alive through the winter is finding the "Goldilocks" environment: not too cold, not too hot, and just the right amount of moisture. If they get too cold, they will freeze and die. If they stay too warm, they might try to start growing in the dark. If they are too wet, they will rot; if they are bone-dry, they will shrivel up.
Finding the Right Temperature
The ideal storage temperature for canna rhizomes is between 45°F and 55°F. This is cool enough to keep them dormant but warm enough to prevent frost damage. Unheated basements, crawl spaces, or a cool corner of a garage (provided it doesn't drop below freezing) are usually the best spots. For more detail, see this guide to canna storage temperatures.
Choosing a Storage Medium
You don't want to leave the rhizomes exposed to the open air all winter, as they will eventually lose too much moisture. Instead, pack them into a container with a moisture-regulating material. Popular choices include:
- Damp Peat Moss: This is the gold standard for many gardeners. It holds just enough moisture to keep the rhizomes plump without making them wet.
- Sawdust or Wood Shavings: Often used for animal bedding, these are inexpensive and work well to insulate the rhizomes.
- Newspaper: You can wrap individual rhizomes in layers of dry newspaper and tuck them into a cardboard box.
- Vermiculite or Perlite: These lightweight minerals are excellent for maintaining a stable environment.
Storage Containers
Plastic bins, cardboard boxes, or even breathable burlap bags can all work. If you use a plastic bin, do not snap the lid on tight. Rhizomes are living things that need a tiny bit of oxygen. Leave the lid cracked or drill a few small air holes in the sides of the bin to allow for air exchange.
Winter Check-ups
Storing cannas is not a "set it and forget it" task. It is a good habit to check on your stored rhizomes about once a month during the winter. This takes only a few minutes but can save your entire collection from a single bad apple.
Open your storage containers and feel a few of the rhizomes.
- If they feel mushy or smell bad: This is a sign of rot. Immediately remove and discard any affected rhizomes so the rot doesn't spread to the healthy ones.
- If they feel very light or look shriveled: They are getting too dry. Use a spray bottle to lightly mist the storage medium (the peat moss or shavings) with a little water. You don't want it wet—just slightly damp to the touch.
- If you see sprouts: The storage area might be too warm or getting too much light. Try to move them to a cooler, darker spot to keep them resting until spring.
Winter Care Summary:
- Store between 45°F and 55°F.
- Use peat moss or shavings to prevent shriveling.
- Check monthly for rot or extreme dryness.
- Keep the storage container slightly ventilated.
Caring for Container-Grown Cannas
If you grow your cannas in large pots or planters, you have an even easier option for winter storage. You don't necessarily have to dig the rhizomes out of the soil at all. For more container-growing guidance, see how to grow canna bulbs in containers.
Once the frost hits and you’ve cut back the foliage, you can simply move the entire container into a cool, frost-free area like a basement or garage. Stop watering the pot entirely. The soil will dry out, and the rhizomes will go dormant right where they are.
In the spring, about six weeks before the last frost, you can bring the pot back into the light, give it a good soak, and watch the new shoots emerge. Every couple of years, you will still need to tip the pot out and divide the rhizomes, as they will eventually become "root-bound" and run out of space to grow.
Preparing for Spring Success
As winter fades and the days grow longer, your cannas will naturally start to "wake up." You might see small pale tips beginning to push through the storage medium. This is an exciting sign that spring is on the way!
In most regions, you can start your cannas indoors in pots about 4 to 6 weeks before the average last frost date. This gives them a "head start" so you can enjoy flowers much earlier in the summer. If you prefer, you can also wait and plant the rhizomes directly into the garden once the soil has warmed to at least 60°F and all danger of frost has passed.
When you are ready to plant, remember the simple rule for depth: bury the rhizome about 4 to 5 inches deep. Position it horizontally in the soil with the "eyes" or any new growth pointing upward. For more detail, see this canna planting depth guide. Give them a sunny spot with rich soil, and they will quickly reward you with that lush, tropical look we all love.
Conclusion
Digging up canna bulbs is a simple and rewarding task that ensures your garden remains vibrant year after year. By waiting for the first frost to signal dormancy and providing a cool, stable environment for the winter, you are participating in a timeless gardening tradition. At Longfield Gardens, we believe that the extra effort of overwintering these tropical favorites is well worth the payoff of spectacular summer blooms.
- Wait for the first frost to blacken foliage before lifting.
- Cure rhizomes in a dry, shaded area for several days.
- Store in a cool, dark place (45°F–55°F) using peat moss or shavings.
- Check monthly for rot or shriveling to ensure spring success.
"A little patience in the fall leads to a lot of beauty in the summer. Taking care of your rhizomes now is the first step toward next year's garden success."
The next step is easy: enjoy the rest of your autumn garden, and once that first frost arrives, head outside with your spade to tuck your cannas away for their winter nap.
FAQ
Can I dig up my cannas before it frosts?
Yes, you can dig them up earlier if you need to, but it is best to wait until the foliage has at least begun to yellow. Waiting for a light frost is ideal because it ensures the plant has finished storing energy in the rhizome for the winter. If you must dig early, leave the foliage attached for a few days in a cool spot to allow the last of the nutrients to move down into the roots.
What happens if I forget to dig them up and the ground freezes?
If only the surface of the soil freezes, your rhizomes might still be okay. However, if the ground freezes several inches deep, the water inside the fleshy rhizomes will turn to ice, causing the cells to burst. This usually leads to the rhizome turning into a mushy, rotten mess when it thaws. If you’ve had a deep freeze, check the rhizomes immediately; if they are still firm, dig them up right away.
Should I use plastic bags to store canna bulbs?
You can use plastic bags, but they must have plenty of ventilation. If a plastic bag is sealed tight, moisture will get trapped inside, which almost always leads to mold and rot. It is much safer to use a cardboard box, a plastic bin with the lid left ajar, or a paper grocery bag. This allows the rhizomes to breathe while the storage medium keeps them from drying out.
Do I need to treat the rhizomes with fungicide before storage?
For most home gardeners, a fungicide is not strictly necessary as long as the rhizomes are cured properly and stored in the right conditions. However, if you have struggled with rot in the past, you can lightly dust the cut ends of the rhizomes with sulfur powder or a general garden fungicide. The most important "medicine" for your plants is simply keeping them cool, dry, and well-ventilated.
