Table of Contents
- Introduction
- Understanding Your Garden Zone
- When to Dig Your Canna Rhizomes
- Step 1: Cutting Back the Foliage
- Step 2: Lifting the Rhizomes Safely
- Step 3: Cleaning and Curing
- Step 4: Dividing Your Cannas
- Step 5: Packing for Winter Storage
- Step 6: The Ideal Storage Environment
- Monitoring Your Rhizomes Through Winter
- Overwintering Potted Cannas
- Preparing for Spring Replanting
- Encouraging Success with Simple Rules
- Summary of the Overwintering Process
- Conclusion
- FAQ
Introduction
There is nothing quite like the tropical flair that canna lilies bring to a summer garden. Their bold, architectural foliage and vibrant blooms create a vacation-like atmosphere right in your backyard. As the season winds down, you don't have to say goodbye to these stunning canna lilies. Learning how to over winter canna bulbs is one of the most rewarding skills a gardener can master because it allows you to enjoy your favorite varieties year after year.
At Longfield Gardens, we want to help you make the most of your garden investments. Saving your canna rhizomes is a practical way to expand your collection without starting from scratch every spring. By following a few straightforward steps, you can ensure your plants remain healthy and dormant through the coldest months. This guide is designed for home gardeners who want a clear, reliable method for digging and storing summer-blooming bulbs.
The process of overwintering is simpler than many people realize. With the right timing and a cool, dry spot for storage, you can protect these cannas from freezing temperatures. This article provides a step-by-step path to successfully preserving your cannas until they are ready to shine again next summer.
Understanding Your Garden Zone
Before you grab your shovel, it is helpful to know whether you actually need to dig up your cannas. While we often call them "bulbs," cannas grow from rhizomes, which are thick underground stems that store energy. These rhizomes are sensitive to freezing temperatures, and their survival depends heavily on your local climate.
In USDA hardiness zones 8 through 10, cannas are generally hardy enough to stay in the ground all year. In these warmer regions, the soil rarely freezes deep enough to damage the rhizomes. If you live in zone 7, you are in a "transition" area. Many gardeners in zone 7 can successfully leave their cannas in the ground if they apply a thick, 6-inch layer of mulch, such as straw or shredded leaves, to insulate the soil.
However, if you live in zone 6 or colder, the winter frost will penetrate deep into the earth and destroy the rhizomes. In these regions, overwintering canna bulbs indoors is necessary. Even if you live in a warmer zone, you might choose to dig them up every few years to divide the clumps and prevent them from becoming overcrowded. Knowing your zone helps you decide whether digging is a requirement or just a helpful maintenance task.
When to Dig Your Canna Rhizomes
Timing is one of the most important factors when you over winter canna bulbs. You want to give the plants as much time as possible to store energy, but you must act before the ground freezes solid. The best signal for digging comes directly from nature.
Wait for the first light frost of autumn. You will know it has happened when the lush green or bronze foliage turns black or dark brown and begins to wilt. This "blackening" of the leaves tells the plant that the growing season is over and it is time to move into a dormant state. The energy from the leaves has been pulled down into the rhizome to fuel next year’s growth.
While a light frost is helpful, do not wait for a hard, deep freeze. A light frost only affects the foliage, but a deep freeze can turn the soil into ice and damage the rhizomes themselves. In most northern states, this window of time usually falls between late September and early November.
Key Takeaway: The ideal time to dig canna rhizomes is immediately after the first frost has blackened the foliage but before the ground has frozen.
Step 1: Cutting Back the Foliage
Once the frost has done its work, your first task is to clear away the spent top growth. This makes the digging process much easier and prevents old, decaying leaves from taking up space in your storage containers.
Use a clean pair of garden shears or a sharp knife to cut the stalks back. Aim to leave about 2 to 4 inches of the stem remaining above the soil line. These short "stubs" serve as convenient handles when you are lifting the rhizomes out of the ground. They also help you identify which way is "up" when it comes time to replant in the spring.
Dispose of the blackened foliage in your compost pile, provided the plants were healthy throughout the summer. If you noticed any significant pest or disease issues during the growing season, it is better to discard the foliage in the trash to avoid carrying those problems over to next year.
Step 2: Lifting the Rhizomes Safely
Lifting cannas requires a bit of care to ensure you don't slice through the rhizomes. Over the summer, a single small rhizome can grow into a massive, heavy clump. You might be surprised at how much they have multiplied since you planted them in the spring.
- Clear the area: Move any mulch or decorative rocks away from the base of the plant so you can see exactly where the stems enter the soil.
- Choose your tool: A garden fork is often better than a shovel because it is less likely to slice through the rhizomes, but a sturdy spade works well if you are careful.
- Dig a wide circle: Start your digging about 6 to 12 inches away from the stems. This ensures you are outside the main mass of the root system.
- Loosen the soil: Push your tool deep into the ground and gently pry upward. Work your way all the way around the plant, loosening the soil from every side.
- Lift the clump: Once the soil is loose, use the stem stubs and your digging tool to lift the entire mass out of the ground.
If the clump is too heavy to lift at once, you can use your spade to carefully divide it while it is still in the hole, but lifting the whole mass is generally safer for the plant's health.
Step 3: Cleaning and Curing
Once the rhizomes are out of the ground, they need a little bit of preparation before they go into storage. This phase, known as "curing," is the secret to preventing rot during the winter.
First, gently shake the clump to remove large chunks of soil. You can use your hands to brush away loose dirt, but avoid scrubbing the rhizomes vigorously. Their "skin" is relatively thin, and any scratches or bruises can become entry points for fungus or rot. Some gardeners prefer to rinse the rhizomes with a garden hose to get them perfectly clean, while others prefer to let the soil dry and then brush it off. Either method works, but if you wash them, you must ensure they dry completely.
After cleaning, place the rhizomes in a warm, dry, and well-ventilated area. A garage, a covered porch, or a basement floor works well. Spread them out in a single layer so air can circulate around them. Let them sit for about 3 to 7 days. This curing process allows the outer surface to toughen up and any remaining stem pieces to dry out.
What to do next:
- Remove large clumps of soil by hand.
- Lay the rhizomes out in a single, uncrowded layer.
- Allow them to dry in a protected area for up to a week.
- Check for any soft or mushy spots and discard those pieces immediately.
Step 4: Dividing Your Cannas
One of the best things about cannas is how much they multiply. Overwintering is the perfect time to divide your plants so you have more to plant next year or to share with friends. You can divide them either in the fall after curing or in the spring before planting.
To divide a clump, look for the "eyes." These are the small, pointed bumps or buds on the rhizome where new growth will emerge. Use a sharp, sterilized knife to cut the rhizome into smaller sections. Each section should have at least two or three healthy eyes and a good portion of the thick rhizome body.
If you divide them in the fall, let the cut ends dry for an extra day before packing them away. This allows the "wound" to callous over, which further protects against rot. If you prefer to keep things simple, you can store the entire large clump and worry about dividing it in the spring.
Step 5: Packing for Winter Storage
Now that your rhizomes are clean, cured, and perhaps divided, it is time to pack them away. The goal of storage is to keep the rhizomes dormant—not so wet that they rot, but not so dry that they shrivel up and die.
Choosing a Storage Container
You have several options for containers. Cardboard boxes, plastic bins (with the lids left slightly ajar), or paper bags all work well. Avoid airtight plastic containers, as they trap moisture and almost always lead to mold and rot.
Using Storage Media
To maintain the right moisture balance, most gardeners surround the rhizomes with a packing material. Popular choices include:
- Peat moss: Excellent for holding just a tiny bit of moisture.
- Vermiculite or Perlite: Very clean and effective at preventing rot.
- Wood shavings or sawdust: A classic choice that provides good insulation.
- Shredded newspaper: An easy, low-cost option.
Place a layer of your chosen material in the bottom of the container. Lay the rhizomes on top so they aren't touching each other, then cover them with more material. You can stack them in layers as long as there is packing material between them.
The "Dry Storage" Method
Some gardeners have success simply placing the cured rhizomes in paper bags without any extra packing material. This works best in environments that have a natural bit of humidity, like a root cellar. If your storage area is very dry, the rhizomes might shrivel too much without peat moss or shavings to protect them.
Step 6: The Ideal Storage Environment
Where you keep your containers is just as important as how you pack them. Cannas need a spot that is "just right"—think of it as a Goldilocks zone for plants.
The ideal temperature is between 40°F and 55°F. This is cold enough to keep the plant dormant but warm enough to prevent the tissue from freezing. A cool basement, an insulated crawl space, or a corner of a frost-free garage are usually the best spots.
Avoid storing them near a furnace or water heater, as the heat will dry them out or trick them into thinking it is spring. Conversely, do not store them in an uninsulated shed where the temperature will drop below freezing. If the rhizomes freeze, they will turn to mush and will not grow when spring arrives.
Monitoring Your Rhizomes Through Winter
Don't just pack your cannas away and forget them until May. A quick monthly check can make the difference between a box of healthy plants and a box of compost.
Once a month, open your containers and take a look. If you see any rhizomes that look soft, fuzzy, or mushy, remove them immediately so the rot doesn't spread to the healthy ones. If the rhizomes look extremely shriveled and brittle, they may be getting too dry. You can lightly mist the storage medium (the peat moss or shavings) with a spray bottle to add a tiny bit of humidity. Be careful not to over-water; the goal is barely damp, never wet.
If you notice the rhizomes are starting to sprout long, pale stems in mid-winter, your storage area is likely too warm. Try moving them to a cooler spot to keep them in their dormant state until the proper planting time.
Overwintering Potted Cannas
If you grow your container-friendly cannas on your patio, you have an even easier option. You don't necessarily have to dig them up at all.
When the first frost hits, cut the foliage back to the soil level just as you would for garden-grown plants. Instead of digging, simply move the entire pot into a cool, frost-free area like a basement or garage. Stop watering the pot entirely. The soil will dry out, and the rhizome will go dormant inside the container.
In the spring, you can bring the pot back outside, refresh the top few inches of soil, and start watering again. However, cannas are fast growers. After a year or two in the same pot, the rhizomes will likely become "pot-bound." At that point, it is best to tip the pot over, remove the mass, and divide the rhizomes to give them more room to grow.
Preparing for Spring Replanting
As winter fades and the ground begins to warm, it is time to think about bringing your cannas back to life. In most regions, you can start your cannas indoors in pots about 4 to 6 weeks before the last frost date to get a head start on the season. This is especially helpful in northern climates where the growing season is shorter.
If you prefer to plant directly into the garden, wait until the soil temperature has reached at least 60°F and there is no longer any danger of frost. Cannas love heat, so they won't do much until the weather is consistently warm.
When you take the rhizomes out of storage, they might look a little shrunken, which is normal. You can soak them in a bucket of lukewarm water for a few hours before planting to "wake them up." Plant them about 4 to 5 inches deep with the eyes or stems pointing upward. With a bit of sunshine and regular water, they will quickly send up new shoots and begin their summer show all over again.
Encouraging Success with Simple Rules
Overwintering is essentially about managing three things: temperature, moisture, and air. If you keep the rhizomes cool but not frozen, slightly dry but not desiccated, and allow for a little bit of airflow, you will find that cannas are incredibly resilient.
We find that most gardening success comes from observing your specific conditions. If your basement is very damp, you might need to use more breathable containers. If your garage is very dry, you might need to check your peat moss more often. Gardening is a continuous learning process, and every year you over winter canna bulbs, you will get a better feel for what works best in your home.
Remember that it is normal to lose a few rhizomes during the winter. Even professional gardeners expect a small percentage of loss. Don't be discouraged if one or two pieces don't make it. Because cannas multiply so quickly, you will likely still have more than enough to create a beautiful display.
Summary of the Overwintering Process
Successfully saving your cannas doesn't require expensive equipment or advanced degrees. It simply requires following the natural rhythm of the plant.
- Wait for the frost: Let nature tell the plant when to go dormant.
- Cut and lift: Remove the dead foliage and carefully dig the clumps.
- Clean and cure: Dry the rhizomes to toughen the skin and prevent rot.
- Store correctly: Use a breathable container and a medium like peat moss in a cool, dark place.
- Check and replant: Monitor during the winter and wait for warm soil in the spring.
Final Action Plan:
- Mark your calendar for the expected first frost in your area.
- Gather your storage supplies (cardboard boxes and peat moss) in advance.
- After the first frost, set aside an afternoon to dig and clean your rhizomes.
- Find a cool, dark spot in your home that stays above freezing all winter.
Conclusion
Overwintering your cannas is a satisfying way to close out the gardening season. It turns a temporary summer plant into a long-term part of your landscape, saving you money and allowing you to grow larger, more impressive displays each year. By protecting these tropical rhizomes from the winter cold, you are ensuring that your garden will be ready to burst into color as soon as the summer heat returns.
At Longfield Gardens, we believe that gardening should be a rewarding and enjoyable experience. Taking the time to care for your plants through the winter is a wonderful way to stay connected to your garden even when the ground is covered in snow. Whether you are a beginner or an experienced gardener, the simple steps of digging, curing, and storing cannas are easy wins that lead to a more beautiful yard.
As you pack your rhizomes away this year, take a moment to appreciate the growth they achieved over the summer. Those thick, healthy rhizomes are full of potential, just waiting for the first warm days of spring to start the cycle again.
Overwintering cannas is a simple, effective way to preserve the tropical beauty of your garden year after year. With a little care and the right storage conditions, your favorite varieties will be ready to thrive again next season.
If you are looking to add new colors or textures to your collection, we invite you to explore our selection of premium cannas and other summer-blooming bulbs. We are here to support you with quality plants and practical advice for every season.
FAQ
Can I store canna bulbs in a garage?
Yes, you can store canna bulbs in a garage as long as the temperature stays above freezing. If your garage is uninsulated and temperatures drop below 40°F, it is better to move them to a basement or crawl space. A corner of the garage that shares a wall with the house is often the warmest and safest spot for storage.
How do I know if my stored canna rhizomes have rotted?
A healthy rhizome should feel firm to the touch, similar to a fresh potato. If a rhizome feels soft, squishy, or slimy, it has rotted and should be thrown away. You may also see fuzzy mold or a sour smell, which are clear signs that the rhizome is no longer viable and should be removed from the container. If you ever have a product-quality concern, our 100% Quality Guarantee explains how we stand behind our plants.
Should I wash the dirt off the rhizomes before storing them?
Washing is a matter of preference. You can rinse them to get them very clean, which makes it easier to see the "eyes" and check for damage. However, if you wash them, you must ensure they dry completely during the curing phase to prevent trapped moisture from causing rot during winter storage. Many gardeners find that simply shaking off the excess soil is sufficient.
When should I take my cannas out of storage in the spring?
You can remove them from storage 4 to 6 weeks before your last expected frost if you want to start them in pots indoors. If you are planting them directly into the garden, wait until the soil is warm (around 60°F) and all danger of frost has passed. Cannas are tropical plants and will not grow well in cold, damp spring soil.