Table of Contents
- Introduction
- Understanding Your Planting Zone
- Why Digging is Necessary for Tropical Rhizomes
- When is the Best Time to Dig?
- How to Dig Canna Rhizomes Properly
- Cleaning and Curing for Storage
- Choosing the Right Storage Medium
- Finding the Ideal Storage Location
- Dividing Cannas: Fall or Spring?
- Overwintering Cannas in Pots
- Bringing Cannas Back to Life in the Spring
- Common Myths About Overwintering Cannas
- Conclusion
- FAQ
Introduction
Few plants bring the high-energy, tropical spirit to a backyard quite like cannas. With their oversized, paddle-shaped leaves and vibrant, torch-like flowers, they turn any standard flower bed into an exotic getaway. One of the best things about these plants is that they are incredibly generous; a single rhizome planted in the spring can multiply into a large, impressive clump by the end of the summer. At Longfield Gardens, we love how cannas bridge the gap between late summer and autumn, providing height and color when other perennials might be starting to fade. If you're shopping for a dramatic selection, start with our [Tall Cannas] collection.
Because cannas are tropical in nature, many gardeners wonder how to handle them once the first frost arrives. The answer to whether you need to dig them up depends almost entirely on where you live. While they are resilient and vigorous during the growing season, their underground rhizomes—which are often called "bulbs"—cannot survive a deep, freezing winter in the ground. If you want a closer look at a standout variety, [Canna Tall Tropicanna Gold] is a popular choice.
In this guide, we will walk you through the simple steps to determine if your cannas need to be lifted for the winter. We will cover the best timing for digging, how to store them safely, and how to ensure they return even stronger next year. This process is a rewarding way to preserve your favorite varieties and enjoy a bigger display each season. For a broader planting overview, see [How to Plant Canna Lily Bulbs: A Step-by-Step Guide].
Whether you are a first-time canna grower or looking to refine your overwintering technique, the following steps will make the process easy and successful. If you want another bold option for gardens or containers, [Canna Tall Tropicanna Black] is a strong pick.
Understanding Your Planting Zone
The first step in deciding if you need to dig up your canna rhizomes is checking your USDA Plant Hardiness Zone. These zones are based on the average annual minimum winter temperature in your area. Because cannas are native to tropical and subtropical regions, they have a specific threshold for cold. You can confirm your zone with the [Hardiness Zone Map].
In general, cannas are considered hardy in zones 8 through 11. In these warmer climates, the ground rarely freezes deep enough to damage the rhizomes. If you live in these zones, you can typically leave your cannas in the ground year-round. They will go dormant as the weather cools and then sprout again once the soil warms up in the spring.
If you live in zone 7, you are in a "swing" zone. In mild winters, cannas may survive in the ground with a thick layer of mulch for protection. However, a particularly harsh or wet winter can still cause them to rot or freeze. Many gardeners in zone 7 choose to dig them up just to be safe, or they plant them in a protected spot near a south-facing wall.
For those of us in zones 3 through 6, canna bulbs must be dug up if you want to keep them for the following year. In these regions, the frozen soil will turn the fleshy rhizomes into mush, effectively ending the plant's life cycle. Taking the time to lift them in the fall is a simple way to protect your investment and keep your garden looking beautiful year after year.
Key Takeaway: Check your USDA zone first. If you are in zone 7 or colder, plan to dig up your cannas or provide significant winter protection to ensure they return.
Why Digging is Necessary for Tropical Rhizomes
To understand why cannas are sensitive to cold, it helps to look at what is happening underground. A canna doesn't grow from a traditional bulb like a tulip; it grows from a rhizome. A rhizome is a thick, fleshy horizontal stem that stores energy and water for the plant. Think of it as the plant’s personal battery pack.
Because these rhizomes are full of moisture, they are very susceptible to freezing. When water inside the plant tissue freezes, it expands and breaks the cell walls. This is what causes a "mushy" texture once the ground thaws. Additionally, cold, wet soil in winter can lead to rot, even if the temperature doesn't drop far below freezing.
By digging up the rhizomes, you are essentially hitting the "pause" button on the plant's growth. You are moving that energy-rich rhizome into a controlled, dry, and cool environment where it can sleep peacefully until the spring sun warms the earth again.
When is the Best Time to Dig?
Timing is one of the most important factors when it comes to overwintering cannas. You want to give the plant as much time as possible to store energy, but you must get the rhizomes out of the ground before the soil itself freezes solid.
The best signal for digging is provided by nature: the first frost. When a light frost hits, the lush green or burgundy leaves of your cannas will turn black or brown and go limp. While this might look a bit sad, it is actually a helpful transition. The frost tells the plant that the growing season is over and it is time to move all its energy down into the rhizome.
We recommend waiting a few days after this first "killing frost" before you start digging. This brief waiting period allows the nutrients in the stems to finish retreating into the rhizomes. However, do not wait until the ground is frozen hard. You want the soil to be workable and the rhizome to be dormant but not frozen.
What to do next:
- Monitor your local weather forecast for the first autumn frost.
- Observe the leaves; once they turn dark and wilted, the plant is ready.
- Gather your tools, including a garden fork or spade and some breathable storage containers.
- Schedule your digging for a dry day if possible, as this makes cleaning the rhizomes much easier.
How to Dig Canna Rhizomes Properly
Digging cannas is a straightforward process, but it requires a bit of care to avoid damaging the fleshy rhizomes. If a rhizome is sliced or heavily bruised, it becomes more vulnerable to mold or rot during its winter nap.
Start by cutting the foliage back. Use a pair of clean garden shears to cut the stems down to about 3 or 4 inches above the soil line. Removing the bulky leaves makes it much easier to see what you are doing and gives you a "handle" to hold onto while you lift the clump.
Next, use a garden fork rather than a shovel if you have one. A fork is less likely to slice through the rhizomes. Start digging about 6 to 12 inches away from the base of the stems. Cannas grow outward, and the rhizomes can spread surprisingly far in a single season. Gently loosen the soil all the way around the clump.
Once the soil is loose, lift the entire clump from underneath. You will likely find that your single spring rhizome has grown into a large, heavy mass of interconnected "fingers." Gently shake off the loose soil, but don't worry about getting them perfectly clean just yet.
Cleaning and Curing for Storage
After the rhizomes are out of the ground, they need a little bit of preparation before they go into storage. This stage is often called "curing," and it is essential for preventing rot. For a practical refresher on this stage of the process, see [How to Overwinter Canna Lily Bulbs].
First, remove the excess soil. You can do this by hand or with a soft brush. Some gardeners like to wash their rhizomes with a hose, but if you do this, you must be extra careful to let them dry completely. Moisture is the biggest enemy of a stored bulb. If the soil is dry and sandy, it should fall away easily. If you have heavy clay soil, you may need to let the clumps sit in a garage or shed for a day to let the soil dry before brushing it off.
Check the rhizomes for any signs of damage or soft spots. If you see a part of the rhizome that looks diseased or mushy, trim it off with a clean knife. Healthy rhizomes should feel firm, similar to a fresh potato or ginger root.
Curing involves letting the rhizomes sit in a dry, frost-free area for a few days. Place them on a piece of cardboard or a newspaper in a well-ventilated spot like a garage or basement. This allows the outer "skin" to toughen up slightly, which helps the rhizome retain its internal moisture without rotting. Usually, two to three days is plenty of time for curing.
Key Takeaway: Curing is a simple but vital step. Letting the rhizomes dry for a few days ensures that no excess moisture is trapped in your storage containers, which prevents mold.
Choosing the Right Storage Medium
The goal of storage is to keep the canna rhizomes cool, dark, and slightly insulated. You want to prevent them from freezing, but you also want to prevent them from drying out so much that they shrivel up and die.
There are several effective ways to pack your cannas for the winter. Here are the most common methods we recommend:
Peat Moss or Vermiculite
This is perhaps the most popular method. Place a layer of dry peat moss, coco coir, or vermiculite in the bottom of a cardboard box or a plastic bin (leave the lid cracked for airflow). Place the rhizomes in the box so they are not touching each other, then cover them with more of the medium. These materials help regulate moisture levels, absorbing any excess dampness while preventing the rhizomes from becoming bone-dry. If you want more seasonal inspiration, browse [Fresh Ideas for Growing Cannas].
Newspaper Wrap
If you only have a few rhizomes, you can wrap each one individually in a few sheets of dry newspaper. Place the wrapped bundles in a paper bag or a cardboard box. The newspaper provides a breathable barrier that protects the rhizomes from temperature fluctuations.
Wood Shavings
Clean wood shavings (like the kind used for animal bedding) are another excellent choice. They allow for great airflow and are very easy to handle in the spring when it's time to unpack.
Regardless of the medium you choose, the most important rule is airflow. Never store canna rhizomes in a sealed, airtight plastic bag. This will trap moisture and almost certainly lead to rot. If you use a plastic tote, leave the lid off or drill several large holes in the sides to let the air circulate.
Finding the Ideal Storage Location
Where you put your containers is just as important as how you pack them. The ideal temperature for storing canna rhizomes is between 40°F and 50°F.
If the temperature is too cold (below 35°F), the rhizomes may freeze and die. If the temperature is too warm (above 55°F), they may think it is spring and start to sprout prematurely in the dark. A cool, unfinished basement, a crawl space, or an insulated garage that stays above freezing are usually the best spots.
If you find that your storage area is a bit too dry and the rhizomes are starting to look wrinkled or shriveled mid-winter, you can lightly mist the storage medium with a spray bottle. You don't want it to be wet—just a tiny bit of humidity to keep the "battery pack" from draining completely.
Dividing Cannas: Fall or Spring?
Because cannas are such vigorous growers, you will often find that the clumps you dig up are quite large. You have the option to divide them so you can plant them in more areas of your garden next year.
We generally recommend waiting until the spring to do your main dividing. When you dig them in the fall, the connections between the rhizomes are still fresh. Every time you cut a rhizome, you create a "wound" that could potentially rot in storage. By waiting until spring, the rhizomes have had all winter to heal, and you can clearly see where the new "eyes" (growth buds) are forming.
If a clump is simply too large to fit into your storage box, it is okay to break it into smaller, manageable sections. Just make sure each section has at least one or two firm "eyes." These look like small, pointed bumps on the surface of the rhizome, similar to the eyes on a potato.
What to do next:
- Label your containers or individual rhizomes with the variety name or color.
- Check your stored rhizomes once a month throughout the winter.
- Quickly remove any that show signs of rot to prevent it from spreading.
- If you notice sprouts starting early, move the container to a slightly cooler spot.
Overwintering Cannas in Pots
If you grow your cannas in large containers during the summer, you have a bit of a shortcut. Instead of digging the rhizomes out of the soil, you can often overwinter the entire pot.
Once the first frost hits and the foliage dies back, cut the stems down to the soil line just as you would with 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 completely; you want the soil to dry out so the plant stays dormant.
In the spring, you can bring the pot back out into the sun, give it a fresh layer of compost, and start watering again. Every couple of years, you will still need to empty the pot to divide the rhizomes, as they will eventually become "root-bound" and outgrow the container. For more container-specific guidance, see [Best Summer Bulbs for Containers].
Bringing Cannas Back to Life in the Spring
The transition from winter storage back to the garden is an exciting time. As the days grow longer and the danger of frost passes, you can start preparing your cannas for their big return.
In most regions, you can plant canna rhizomes directly into the ground once the soil has warmed to about 60°F. Cannas love heat, so there is no rush to get them in the ground while the earth is still chilly and damp.
If you want a head start, you can "wake up" your rhizomes indoors about 4 to 6 weeks before the last frost date. Place the rhizomes in pots with some moist potting soil and keep them in a warm, sunny window. By the time the weather is consistently warm outside, you will have established plants ready to take off and bloom earlier than those planted directly in the garden. For a deeper dive into timing, see [When Do I Plant Canna Lily Bulbs? Best Timing Tips].
When replanting, place the rhizomes about 4 to 5 inches deep and space them 1 to 2 feet apart, depending on the variety. Make sure the "eyes" are pointing upward. Within a few weeks, you'll see those iconic pointed shoots breaking through the soil, starting the tropical cycle all over again.
Common Myths About Overwintering Cannas
There is a lot of advice floating around the internet about cannas, and some of it can be a bit confusing. Let’s clear up a few common misconceptions to keep your gardening experience stress-free. For another helpful overview, read [Understanding Cold Hardiness and Heat Tolerance].
One common myth is that cannas must be washed with a bleach solution before storage. While some gardeners do this to kill bacteria, it isn't usually necessary for the home gardener. As long as your rhizomes are healthy, dry, and stored in a clean medium, they should do just fine.
Another myth is that you can't leave cannas in the ground in Zone 6 or 7. While it is risky, many gardeners find success by using "the mulch method." This involves cutting the plants back and topping them with a foot or more of straw or leaves, covered with a tarp to keep the area dry. While we generally recommend digging in these zones for guaranteed results, gardening is all about experimentation. If you have extra rhizomes, you might try leaving a few in the ground to see how they fare in your specific microclimate.
Finally, don't worry if your stored rhizomes look a little "ugly" or dirty when you pull them out in the spring. As long as they are firm and have visible eyes, they are ready to grow. They don't need to be pretty to produce stunning flowers!
Conclusion
Overwintering cannas is one of those gardening tasks that sounds more difficult than it actually is. By following the simple rhythm of the seasons—waiting for the frost, lifting the rhizomes, and giving them a cool place to rest—you can enjoy these tropical beauties for many years. It is a wonderful way to grow your garden collection without having to buy new plants every spring.
At Longfield Gardens, we want to help you feel confident in every stage of the growing process. Whether you are tending to a single pot of cannas on a balcony or a massive border of towering blooms, the effort you put in during the fall will pay off in a spectacular summer display.
As you head out to your garden this autumn, remember that those dormant rhizomes are full of potential. Treat them well, keep them dry, and look forward to the lush, tropical paradise they will create when the sun returns.
Final Thoughts: Gardening is a journey of learning what works best for your specific soil and climate. Digging cannas is a small investment of time that yields a huge reward in color and texture. If you haven't tried it before, make this the year you save your favorite varieties!
FAQ
Can I leave cannas in the ground if I live in Zone 7?
It depends on the winter. In a mild year, cannas often survive in Zone 7 if they are buried under a thick layer of mulch (about 6–8 inches) to protect the soil from freezing. However, a prolonged deep freeze or a very wet winter can still cause them to rot. To be 100% safe, we recommend digging them up, but many Zone 7 gardeners successfully leave them in the ground in protected areas. If you're planning next spring's color now, take a look at [Canna Tall Tropicanna].
What happens if I forget to dig up my cannas before a hard freeze?
If the foliage dies back from a light frost, the rhizomes are usually fine. However, if the ground itself freezes several inches deep, the rhizomes will likely be damaged beyond repair. If you realize you’ve waited too long, dig them up immediately and check for firmness. If they are still hard and not mushy, they may still be viable, but their chances of survival are lower.
Do I need to water the canna rhizomes while they are in storage?
Generally, no. You want the rhizomes to stay dormant, and moisture can trigger growth or rot. However, if you check them in mid-winter and they look extremely shriveled or bone-dry, you can lightly mist the packing material with a spray bottle. The goal is to keep them from drying out completely without making them wet.
Can I store my canna rhizomes in the refrigerator?
While a refrigerator provides the right temperature (around 40°F), it is often too humid or lacks enough airflow for long-term rhizome storage. Additionally, many modern refrigerators are "frost-free," which can actually dehydrate the rhizomes too quickly. A cool basement or insulated garage is a much better environment for overwintering your plants.