Table of Contents
- Introduction
- When to Start the Overwintering Process
- Why Save Your Canna Rhizomes?
- Tools You Will Need
- Step-by-Step Guide to Digging Canna Bulbs
- Cleaning and Preparing Rhizomes for Storage
- The Curing Process: Why It Matters
- Choosing the Right Storage Container and Medium
- Ideal Storage Conditions: Temperature and Humidity
- Monitoring Your Cannas During Winter
- Dividing Canna Rhizomes
- Overwintering Cannas Grown in Containers
- Troubleshooting Common Storage Issues
- Waking Up Your Cannas in Spring
- Conclusion
- FAQ
Introduction
Canna lilies are the undisputed stars of the summer garden. Their oversized, tropical foliage and brilliant flowers bring a sense of exotic luxury to any backyard or patio. Whether you love the deep bronze leaves of 'Wyoming' or the striking stripes of Pretoria, these plants make a bold statement. At Longfield Gardens, we believe that the joy of growing cannas should last for many years, not just a single season.
Because cannas are tropical plants, they thrive in the heat but cannot survive a freezing winter in most parts of the country. Learning how to overwinter canna bulbs—which are technically called rhizomes—is a simple skill that saves you money and lets you grow even larger, more impressive displays each year. This guide is for any gardener who wants to keep their favorite varieties safe until spring returns. For especially dramatic options, see our Tall Cannas collection.
We will walk you through the timing, digging, and storage methods that ensure your plants stay healthy and dormant through the cold months. By following a few basic steps, you can enjoy these spectacular tropicals year after year. For a broader overview, see our All About Cannas guide.
When to Start the Overwintering Process
The best time to begin the overwintering process is right after the first light frost in the fall. You will know it is time when the lush green or bronze leaves turn black or brown after a cold night. This change in color is a signal that the plant has finished its work for the year. The foliage has sent the last of its energy down into the rhizomes to store for the following spring.
While a light frost kills the leaves, the soil usually stays warm for a few more weeks. You do not want to wait until the ground freezes solid. If the soil freezes deep enough to reach the rhizomes, they may turn to mush and will not survive. Most gardeners aim to dig their cannas in late September, October, or November, depending on their local climate.
If you live in a region that does not experience frost, such as the southern tip of Florida or parts of California, you may not need to dig them up at all. However, for most of the United States, bringing them indoors is the only way to guarantee they return. Watching the weather forecast as autumn progresses is the most reliable way to time your harvest.
Why Save Your Canna Rhizomes?
One of the most rewarding aspects of gardening is watching your collection grow. Canna rhizomes are incredibly productive. Over a single summer, one small rhizome can grow into a massive clump with several new offshoots. By saving these clumps, you are essentially getting free plants for your garden next year.
Saving your own stock also ensures you have the specific varieties you love. While we offer a wide selection of premium bulbs at Longfield Gardens, overwintering your existing plants allows you to build a massive "tropical forest" effect over time. Large rhizomes often produce more vigorous plants and earlier blooms than smaller, younger ones.
This practice is also very sustainable. Instead of treating these beautiful plants as annuals and throwing them away, you are participating in the natural cycle of the garden. It is a satisfying task that marks the transition from the busy growing season to the quiet rest of winter.
Tools You Will Need
Before you head out to the garden, gather a few basic supplies. Having everything ready makes the job much faster and prevents unnecessary damage to the plants.
- A sturdy garden fork or a sharp spade.
- Hand pruners or loppers for cutting back heavy stems.
- A garden hose with a spray nozzle.
- Cardboard boxes, plastic bins (without lids), or paper grocery bags.
- Storage medium, such as peat moss, vermiculite, or wood shavings.
- A permanent marker for labeling.
A garden fork is often better than a shovel for this job. The tines of the fork allow you to lift the soil and the rhizomes without accidentally slicing through the fleshy roots as easily as a solid blade might.
Step-by-Step Guide to Digging Canna Bulbs
The process of lifting cannas is straightforward. Start by cutting the stalks back to about 3 or 4 inches above the soil line. This gives you a "handle" to grab while you work but removes the heavy, dead foliage that would otherwise get in your way. Dispose of the dead leaves in your compost pile or yard waste.
Next, use your garden fork to loosen the soil around the clump. Start about a foot away from the base of the stems. Cannas can spread horizontally quite far during the summer, and you want to avoid stabbing the rhizomes. Work your way around the entire plant, gently prying upward to break the soil's grip.
Once the soil is loose, lift the entire clump out of the ground. It might be surprisingly heavy, especially if your soil is damp. Gently shake the clump to remove large chunks of dirt. Do not worry if the clump breaks into a few large pieces during this step. Canna rhizomes are tough, and natural breaks often happen where the plant was already planning to divide.
Key Takeaway: Always dig wider than you think you need to. Starting your shovel or fork 12 inches away from the stems helps protect the new "eyes" forming on the outer edges of the rhizomes.
Cleaning and Preparing Rhizomes for Storage
Once the rhizomes are out of the ground, they need a bit of cleaning. You can use your hands to brush away loose soil. Some gardeners prefer to use a garden hose to wash the rhizomes completely clean. Washing makes it much easier to inspect the health of the plant and see where the "eyes" or growing points are located.
If you choose to wash them, be gentle. You do not want to scrub so hard that you break the skin of the rhizome. The skin helps protect the plant from drying out too fast. After washing, look for any soft spots or signs of damage. If a part of the rhizome feels mushy like a rotten potato, trim that section away with clean pruners.
If you discover any small, white grubs or other pests, rinse them away. Starting with clean, healthy material is the best way to ensure success. If you have several different varieties, such as the vibrant 'Red King Humbert' and the yellow-flowered City of Portland, label them immediately. It is easy to forget which is which once the leaves are gone.
The Curing Process: Why It Matters
Curing is a fancy word for letting the rhizomes dry out slightly before they go into long-term storage. This is a vital step. If you put wet, freshly dug rhizomes directly into a box, they are much more likely to rot or develop mold. Curing allows the outer skin to toughen up and any cut surfaces to "callous" over.
Place your cleaned rhizomes in a single layer on a piece of cardboard or a mesh screen. Keep them in a dry, frost-free location like a garage, shed, or basement. Avoid placing them in direct sunlight, as this can cause them to overheat or dry out too much.
Let the rhizomes sit for two to three days. You aren't trying to dry them out completely—they should still feel heavy and firm—but the surface should be dry to the touch. Once they feel "cured," they are ready to be packed away for their winter nap.
Choosing the Right Storage Container and Medium
The goal of winter storage is to keep the rhizomes dormant, cool, and slightly hydrated. You do not want them to be bone-dry, but you also do not want them to be wet. The container and the packing material you choose will help balance this moisture.
Cardboard boxes are an excellent choice because they allow for a small amount of airflow. You can also use plastic storage bins, but do not put the lids on tightly. If you use a plastic bin, leave the top open or drill several holes in the sides to prevent moisture from getting trapped inside.
For the packing medium, use one of the following:
- Peat Moss: This is the most popular choice. It holds a tiny bit of moisture but stays fluffy.
- Vermiculite: A mineral that provides excellent insulation and moisture control.
- Wood Shavings: Often sold as pet bedding, these are cheap and effective.
- Newspaper: You can wrap individual rhizomes in sheets of dry newspaper.
Start by putting a 2-inch layer of your chosen medium in the bottom of the box. Place a layer of rhizomes on top, making sure they do not touch each other. If one starts to rot, you don't want it to spread to the others. Cover that layer with more medium and repeat until the box is full.
Ideal Storage Conditions: Temperature and Humidity
Where you keep your boxes is just as important as how you pack them. Cannas need a spot that is dark, cool, and dry. The ideal temperature range is between 45°F and 55°F.
If the temperature stays above 60°F, the rhizomes might think it is spring and start to grow in the box. If this happens, they will use up their stored energy too early and will be weak when you plant them. If the temperature drops below 40°F, you run the risk of frost damage.
Unheated basements, crawl spaces, or an insulated garage are usually the best spots. Avoid rooms with furnaces or water heaters, as these areas are often too warm and dry. If you are worried about the temperature, you can place a simple indoor/outdoor thermometer near your boxes to monitor the conditions throughout the winter.
Monitoring Your Cannas During Winter
Overwintering is not a "set it and forget it" task. To get the best results, check on your rhizomes about once a month. This only takes a few minutes but can save your entire collection.
Open the boxes and feel a few of the rhizomes. They should feel firm, like a fresh ginger root or a potato. If you notice any that are turning soft or smelling bad, remove them immediately and throw them away. This prevents rot from spreading to the healthy plants.
If the rhizomes feel very light or look shriveled, they might be getting too dry. In this case, use a spray bottle to lightly mist the packing medium with water. You don't want it to be wet—just a very slight dampness like a wrung-out sponge. Usually, one or two light mists over the entire winter is all they need.
Key Takeaway: Monthly checks are your best defense. Catching a single rotten rhizome early can save the dozens of healthy ones packed around it.
Dividing Canna Rhizomes
You can divide your cannas either in the fall when you dig them up or in the spring before you plant them. Most gardeners prefer to wait until spring because the "eyes" (the small bumps where new stems will grow) are easier to see as the plant begins to wake up.
However, if your clumps are too large to fit into your storage boxes, you can divide them in the fall. Simply pull the rhizomes apart or use a clean, sharp knife to cut them into smaller sections. Each section must have at least one "eye" to grow a new plant. A piece with two or three eyes is even better and will produce a fuller plant faster.
If you cut the rhizomes, let the cut ends dry for a full day before packing them away. This allows the "wound" to callous, which is a natural defense against fungus and rot. At us, we find that dividing every two or three years is the best way to keep your plants vigorous and healthy.
Overwintering Cannas Grown in Containers
If you grow your cannas in pots, the process is even easier. You have two main options for container-grown plants. For container ideas, browse our Summer Blooming Bulbs for Containers.
The first option is to treat them exactly like garden cannas. Dig the rhizomes out of the pot, clean them, and store them in boxes. This is the best choice if the plant has become "root-bound," meaning the roots and rhizomes have filled the entire pot and have no more room to grow.
The second option is to store the entire pot. Once the foliage has died back from frost, cut the stems down to the soil line. Move the entire pot into a cool, dark, frost-free area like a basement. Stop watering the pot entirely. The soil will dry out, and the plant will go into a deep dormancy. In the spring, you can bring the pot back out, give it a fresh layer of compost, and start watering it again.
Storing the whole pot is a great "shortcut" for busy gardeners. However, keep in mind that cannas grow very fast. Even a large pot will eventually become too crowded, so you will still need to empty the pot and divide the rhizomes every year or two to keep the plants blooming well.
Troubleshooting Common Storage Issues
Even with the best care, you might run into a few common issues. The key is to stay positive and make small adjustments.
If you find mold on the surface of your rhizomes, it usually means the storage medium is too wet or there isn't enough airflow. Remove the affected plants, wipe off the mold, and let them dry out in the open air for a day. Move the boxes to a spot with better air circulation and use a drier packing material.
If your rhizomes are shriveling up and feeling "hollow," the air is too dry. This is common in modern basements with high-efficiency furnaces that strip moisture from the air. Simply mist the packing material more frequently or wrap the boxes loosely in plastic to help hold in a little more humidity.
If your cannas start growing long, pale white sprouts in February or March, they are likely too warm. Move them to a cooler spot. These early sprouts are fragile and often break during planting, but do not worry. The rhizome has plenty of energy to push out new, stronger sprouts once it is planted in warm soil.
Waking Up Your Cannas in Spring
When the days start to get longer and the threat of hard frost passes, it is time to think about spring. You can plant canna rhizomes directly in the ground once the soil has warmed to at least 60°F and there is no danger of frost. In many regions, this is around the same time you would plant tomatoes. For planting depth details, see our How Deep to Plant a Canna Bulb guide.
If you want earlier blooms, you can "pre-start" your cannas indoors. About four to six weeks before the last frost date, take the rhizomes out of storage. Plant them in pots with moist potting soil and place them in a warm, sunny window or under grow lights.
By the time the weather is warm enough to plant outside, you will already have healthy green shoots several inches tall. This "head start" is especially helpful for gardeners in northern states who have a shorter growing season. Transition them to the outdoors slowly by giving them a few hours of sun each day for a week before planting them in their permanent home.
Conclusion
Overwintering canna bulbs is a rewarding way to preserve the beauty of your summer garden. By taking the time to dig, clean, and store these tropical treasures, you ensure a spectacular display for the coming year. This process turns a single purchase into a lifelong collection of vibrant colors and architectural foliage.
At Longfield Gardens, we want every gardener to feel confident in their ability to grow and maintain these stunning plants. Our 100% Quality Guarantee helps make that possible. Remember that gardening is a journey of learning and observation. Every season you save your rhizomes, you learn more about what works best for your specific climate and home.
Next Steps for Success:
- Check your local frost dates to time your digging correctly.
- Gather your storage supplies like peat moss and cardboard boxes now.
- Label your varieties clearly so you can plan next year’s garden design.
- Keep your stored rhizomes in a cool, dark place and check them monthly.
Overwintering cannas is a simple, effective way to turn a one-season flower into a permanent part of your garden landscape.
We invite you to explore our selection of cannas and our Shop All Spring-Planted Bulbs collection to find the perfect additions to your yard next spring.
FAQ
Can I leave my canna bulbs in the ground if I mulch them heavily?
This depends on your USDA hardiness zone; our Hardiness Zone Map can help you check. If you live in Zone 7, you can often leave cannas in the ground if you apply 6–8 inches of straw or leaf mulch for insulation. In Zone 6 or colder, the ground usually freezes too deep for mulch to protect the rhizomes, so digging them up is the safest option.
Do I need to wash the dirt off the rhizomes before storing them?
While it isn't strictly necessary to wash them, it is highly recommended. Washing the soil off allows you to see any rot, soft spots, or hidden pests. It also makes the rhizomes much cleaner to handle and store inside your home, reducing the risk of bringing soil-borne fungi into your storage area.
What should I do if my stored canna rhizomes look shriveled?
If the rhizomes look shriveled or feel unusually light, they are losing too much moisture. Use a spray bottle to lightly mist the storage medium (like peat moss or wood shavings) with water. You want the medium to feel barely damp, which will help the rhizomes rehydrate without causing them to rot.
When is the earliest I can replant my cannas in the spring?
Wait until the soil has warmed up and all danger of frost has passed. Cannas are tropical plants and will not grow in cold soil; they may even rot if the ground is cold and wet. In most areas, the best time to plant is mid-to-late May or whenever you would typically plant other warm-weather favorites like dahlias or zinnias.