Table of Contents
- Introduction
- Understanding the Canna Life Cycle
- The Role of USDA Hardiness Zones
- The Visual Signals for Digging
- How to Dig Up Canna Rhizomes
- What to Do Next: Post-Digging Checklist
- Curing: The Essential Step
- Inspecting and Dividing
- Storage Conditions for Winter
- Special Considerations for Container Cannas
- When to Put Them Back in the Ground
- Troubleshooting Common Timing Questions
- Safety and Practical Tips
- Conclusion
- FAQ
Introduction
The sight of canna lilies in full bloom is one of the highlights of the summer garden. Their bold, tropical foliage and vibrant flowers bring a sense of exotic beauty to any backyard or patio. Whether you grow tall, stately cannas or compact versions for containers, these plants are remarkably reliable and easy to enjoy. At Longfield Gardens, we want to help you keep that beauty coming back year after year.
Because cannas are tropical plants, they thrive in the heat but are sensitive to freezing temperatures. In many parts of the United States, the ground gets cold enough in winter to damage the underground structures that store the plant's energy. Knowing exactly when to lift these rhizomes—often called "bulbs"—is the key to a successful gardening cycle.
This guide is designed for home gardeners who want to protect their investment and enjoy their favorite cannas for many seasons. For smaller spaces, our Short Cannas collection is a useful place to start. We will cover the specific visual cues to look for, how the timing changes based on your location, and the best way to handle the transition from the garden to winter storage.
The secret to a thriving canna garden next year is understanding how to time your fall harvest correctly. For a broader overview, see All About Cannas.
Understanding the Canna Life Cycle
To understand when to take canna bulbs out of the ground, it helps to know what is happening beneath the soil. While we often call them bulbs, cannas actually grow from rhizomes. These are thick, fleshy horizontal stems that store food and water for the plant.
During the summer, the leaves capture sunlight and turn it into energy. This energy is sent down to the rhizome to fuel growth and future blooms. As the season winds down, the plant begins to move its remaining resources into the rhizome to prepare for a period of dormancy.
In their native tropical environments, cannas do not experience a freezing winter. In most of North America, however, the frost will eventually kill the foliage. This serves as a natural signal for the plant to stop growing and rest. If you leave the rhizomes in the ground where the soil freezes, the water inside the fleshy tissues will expand and cause the cells to burst. This leads to rot and the loss of the plant.
The Role of USDA Hardiness Zones
The first step in deciding when to dig up your cannas is knowing your USDA Hardiness Zone Map. This map is a helpful tool that tells you how cold your winters typically get. You can find your zone by entering your zip code into any online gardening zone finder.
Zones 8 to 10
In these warmer regions, the ground rarely freezes deep enough to harm cannas. If you live in zone 8, 9, or 10, you can usually leave your cannas in the ground year-round. You may choose to cut the foliage back after it turns brown and apply a few inches of mulch for extra insulation. This acts as a cozy blanket that keeps the soil temperature stable.
Zone 7
Gardeners in zone 7 live in a "transition zone." In many years, cannas will survive the winter if they are planted in a protected spot, such as near the south-facing wall of a house. However, a particularly cold winter can still be a risk. Many gardeners in this zone choose to dig up at least a few of their favorite varieties as insurance, while leaving the rest in the ground with a thick layer of straw or mulch.
Zones 3 to 6
If you live in zone 6 or colder, cannas must be lifted and stored indoors. The frozen ground in these areas will reliably destroy the rhizomes. In these regions, the timing of your harvest is critical to ensuring the plant has stored enough energy to survive the winter and sprout again in the spring.
The Visual Signals for Digging
Timing beats tricks every time when it comes to fall gardening. Instead of following a specific date on the calendar, it is much more effective to watch your plants and your local weather forecast.
The First Frost
The most common and reliable signal to dig up cannas is the first light frost. You will know this has happened when the lush green leaves suddenly turn black or dark brown and begin to wilt. This usually happens when temperatures dip just below 32°F for a few hours at night.
While it might look like the plant is "ruined," this is actually exactly what you want to see. The frost kills the top growth but does not immediately affect the rhizomes protected by the soil. This signal tells the plant that the growing season is over. Taking them out of the ground immediately after this frost ensures that the rhizome is at its peak energy storage.
The Yellowing Stage
If you live in an area where the first frost arrives very late, you might notice your cannas starting to turn yellow or look "tired" on their own. This is a sign that the plant is naturally entering dormancy as the days get shorter and the light intensity decreases. If your foliage has completely yellowed and the weather is consistently turning cold, you can begin the digging process even if a frost hasn't hit yet.
Avoiding the Deep Freeze
The one thing you want to avoid is waiting too long. While a light frost on the leaves is beneficial, a deep freeze that penetrates the soil is a problem. If the ground begins to freeze solid, it can damage the rhizomes. As a general rule, aim to have your cannas out of the ground within a week or two of the first foliage-killing frost.
Key Takeaway: The ideal time to dig up cannas is shortly after the first light frost has blackened the leaves. This allows the plant to maximize its energy storage while protecting the rhizomes from a deep ground freeze.
How to Dig Up Canna Rhizomes
Once the timing is right, the process of lifting the rhizomes is straightforward. Having the right tools and a gentle touch will help prevent damage that can lead to rot during storage.
Prepare the Foliage
Start by cutting the stems back. Use a clean pair of garden pruners or a sharp knife to cut the stalks down to about 3 or 4 inches above the soil line. This "handle" makes it much easier to see where the plant is and gives you something to hold onto without damaging the eyes of the rhizome.
Digging Wide
Canna rhizomes can grow quite large over a single summer. One small piece planted in May can turn into a heavy clump by October. To avoid accidentally slicing through the fleshy rhizomes, start digging about 10 to 12 inches away from the center of the plant.
Use a sturdy garden shovel or a garden fork. Gently push the tool into the soil and lean back to lift the clump. Work your way around the entire plant, loosening the soil as you go. Once the clump is loose, you can lift it out of the ground entirely.
Cleaning the Clump
Once the cannas are out of the hole, gently shake off the excess soil. You can use your hands to brush away large clods of dirt. Some gardeners prefer to use a garden hose to rinse the rhizomes clean. This makes it easier to see the "eyes"—the small, pointed bumps where next year’s growth will emerge. If you do rinse them, it is vital to let them dry completely before moving to the next step.
What to Do Next: Post-Digging Checklist
- Cut stalks to 3-4 inches above the soil.
- Dig a wide circle around the plant to avoid damage.
- Gently lift the clump and remove large pieces of soil.
- If the soil is very wet, let the clumps sit in a garage or shed for a few hours to dry.
- Move the rhizomes to a protected area for curing.
Curing: The Essential Step
One of the most important parts of taking cannas out of the ground is what happens immediately afterward. Curing is the process of allowing the outer skin of the rhizome to toughen up. This simple step helps the plant resist mold and rot during the long winter months. For step-by-step overwintering help, see How to Manage Overwintering Canna Lily Bulbs.
After digging and cleaning, place your canna clumps in a dry, well-ventilated area. A garage, a shed, or even a covered porch works well, provided the temperatures stay above freezing. Spread them out so they are not touching each other.
Let the rhizomes air dry for about 3 to 7 days. During this time, the cut stems will start to dry out, and any remaining soil will become easier to brush away. A properly cured rhizome will feel firm and dry to the touch, not squishy or damp.
Inspecting and Dividing
Before you put your cannas away for the winter, take a moment to inspect them. Healthy rhizomes should be firm and relatively heavy for their size. If you notice any soft, mushy spots or areas that look like they are rotting, cut those sections away with a clean knife.
You can also choose to divide your cannas at this time. Because cannas are so prolific, you will likely have many more than you started with. If you want a middle-ground option, browse our Medium Cannas collection. To divide them, simply break or cut the clumps into smaller sections. Each section must have at least one "eye" or growing point to produce a plant next year. Many gardeners prefer to keep their clumps in groups of 3 to 5 eyes for a more substantial plant in the spring.
Storage Conditions for Winter
Storing canna bulbs is all about finding the right balance of temperature and moisture. You want a spot that is cool enough to keep the plant dormant but warm enough to prevent freezing.
Temperature
The ideal storage temperature is between 40°F and 50°F. If the area is too warm, the cannas may try to sprout prematurely. If it is too cold, they may suffer from frost damage. Unheated basements, crawl spaces, or insulated garages are often the best locations.
Humidity and Packing Material
You want to keep the rhizomes from drying out completely, but you also don't want them to stay wet. To achieve this, pack them in a breathable material. Common choices include:
- Peat moss: Helps maintain a steady moisture level.
- Vermiculite or Perlite: Provides good insulation and keeps the rhizomes separated.
- Shredded newspaper: An easy, recycled option that allows for airflow.
- Wood shavings: Often sold as pet bedding, these are excellent for storage.
Place a layer of your chosen material in a cardboard box, plastic bin (with the lid left slightly ajar), or a paper bag. Place the rhizomes inside, ensuring they aren't crowded, and cover them with more material.
Monitoring During Winter
Gardening doesn't completely stop just because the plants are in boxes. Check on your stored cannas once a month. If they look shriveled or very dry, give them a light misting with water to rehydrate the packing material. If you find any that have started to rot, remove them immediately so the problem doesn't spread to the healthy ones.
Special Considerations for Container Cannas
If you grow your cannas in pots, the process is even easier. For more container guidance, see How to Grow Summer Bulbs in Containers. You don't necessarily have to dig them out of the soil. Once the first frost hits, cut the foliage back to the soil line. Move the entire container into a cool, dark, frost-free area like a basement or garage.
Stop watering the container entirely. The soil will dry out, and the cannas will go dormant in the pot. In the spring, you can simply bring the pot back outside, resume watering, and wait for the new growth to appear. If the pot has become too crowded over the summer, you can dump it out in the spring and divide the rhizomes then.
When to Put Them Back in the Ground
The journey of the canna bulb comes full circle in the spring. Just as the timing of the fall harvest is dictated by the weather, so is the timing of spring planting.
Cannas love warm soil. For spring replanting details, see How to Plant Canna Lily Bulbs. We recommend waiting to replant your rhizomes until the danger of frost has passed and the soil temperature has reached at least 60°F. This is usually around the same time you would plant tomatoes or peppers in your garden.
If you want to get a head start, you can "wake up" your cannas by planting them in pots indoors about 4 to 6 weeks before your last frost date. For that method, see Starting Canna Lily Bulbs Indoors. Place them in a sunny window or under grow lights. By the time the weather is warm enough to move them outside, you will already have several inches of growth, leading to earlier blooms in the summer.
Troubleshooting Common Timing Questions
Sometimes the weather doesn't follow the rules, and you might find yourself unsure of what to do. Here are a few common scenarios:
What if I miss the first frost?
If you forget to dig up your cannas and a second or third frost happens, don't worry. As long as the ground has not frozen solid, the rhizomes are likely still healthy. Get them out of the ground as soon as possible once you notice the foliage has died back.
What if I dig them up too early?
If you have to dig them up before a frost—perhaps because you are moving or expect a very early winter—the plants will be fine. They might not have stored quite as much energy as they would have with a few more weeks of sun, but they are very resilient. Ensure they have a proper curing period to help them enter dormancy.
Can I leave them in the ground with just mulch?
This depends entirely on your zone. In Zone 8 and 9, mulch is usually enough. In Zone 7, it is a calculated risk. In Zone 6 and colder, mulch will not prevent the deep ground freeze from reaching the rhizomes. At Longfield Gardens, we always suggest that if you really love a specific variety, it is better to be safe and store it indoors.
Safety and Practical Tips
While canna lilies are generally considered non-toxic to cats, dogs, and horses, it is always a good practice to keep any stored bulbs or rhizomes out of reach of pets and children. The fleshy roots can be a choking hazard, and you don't want your hard work to be dug up by a curious puppy in the basement.
Always remember that gardening success is a blend of following the rules and observing your unique environment. Soil types, the amount of sun your garden receives, and the specific microclimates in your yard can all influence when your cannas are ready for their winter nap. For more ways to shop, see our Shop Spring Planted Bulbs by Type.
Key Takeaway: Success with cannas comes from matching your actions to the weather. By watching for the first frost and providing a cool, dry winter home, you ensure your garden will be filled with tropical color year after year.
Conclusion
Taking canna bulbs out of the ground is a rewarding part of the seasonal rhythm of gardening. It allows you to preserve your favorite varieties, multiply your plant collection for free, and ensure that your garden is ready for a fresh start each spring. For more planning inspiration, browse our Shop Spring Planted Collections.
- Wait for the first light frost to blacken the foliage before digging.
- Dig a wide circle to protect the fleshy rhizomes from damage.
- Cure the rhizomes in a dry, ventilated area for several days.
- Store in a cool, dark, frost-free location between 40°F and 50°F.
The beauty of cannas is well worth the small effort of winter storage. With these simple steps, you can look forward to a vibrant and colorful display every summer. For a broader selection, see Shop All - Shop Spring Planted Bulbs.
"The best time to plan for next year's garden is while you are putting this year's garden to bed. Protecting your cannas now is the first step toward a beautiful summer display."
FAQ
How long can I leave canna bulbs in the ground after a frost?
You should aim to dig up your canna rhizomes within one to two weeks after the first frost kills the foliage. While the rhizomes are safe as long as the ground isn't frozen, waiting too long increases the risk of soil-borne diseases or a sudden deep freeze. It is best to lift them while the weather is still manageable and the soil is not yet frozen solid.
Do I need to wash the dirt off the rhizomes before storing them?
While you don't have to wash them, many gardeners prefer to rinse away the soil to inspect for pests or rot. If you do choose to wash them, it is critical that you allow the rhizomes to dry completely during the curing process before packing them away. If you prefer not to wash them, simply brush off the large clumps of soil once they have dried slightly.
Can I store canna rhizomes in the garage?
You can store canna rhizomes in a garage as long as the temperature stays above freezing (32°F) all winter. If your garage is uninsulated and temperatures drop significantly, the rhizomes will likely freeze and rot. An attached garage or a basement is usually a safer bet for maintaining the ideal 40°F to 50°F range. For shipping details and order timing, see our Shipping Information.
Why did my stored canna bulbs rot last year?
Rot is usually caused by one of three things: the rhizomes were not cured properly before storage, they were stored in a place that was too damp, or they were damaged during the digging process. To prevent this, ensure they air dry for several days after digging, cut away any bruised sections, and store them in a breathable material like peat moss or wood shavings. Inspecting them monthly and removing any soft pieces will also prevent rot from spreading.