Table of Contents
- Introduction
- Understanding the Canna Life Cycle
- Knowing Your USDA Hardiness Zone
- When to Dig Your Canna Bulbs
- Tools You Will Need
- Step-by-Step Guide to Digging and Cleaning
- The Importance of Curing
- Dividing Canna Rhizomes
- Choosing the Right Storage Method
- Finding the Best Storage Location
- Mid-Winter Checkups
- Waking Them Up in Spring
- Success with Different Canna Varieties
- Simple Tips for Healthy Rhizomes
- Conclusion
- FAQ
Introduction
Canna lilies bring a bold, tropical flair to the garden that is hard to match with any other plant. Their oversized leaves and vibrant, torch-like flowers make every summer day feel like a vacation in your own backyard. These plants are incredibly rewarding to grow, especially when you realize that one season of beauty can easily turn into many more.
At Longfield Gardens, we want to help you enjoy your favorite spring-planted bulbs year after year. While cannas are tropical by nature, you do not need to live in a warm climate to keep these plants as permanent members of your garden. With a few simple steps in the fall, you can safely store these plants through the coldest months and have them ready to glow again next spring.
This guide will walk you through everything you need to know about overwintering canna bulbs. We will cover when to dig them up, how to prepare them for their winter nap, and the best ways to store them so they stay healthy and firm. If you need help timing a new order, our shipping information page is a useful reference. By following these steps, you can save money and grow an even more impressive display each year as your collection multiplies.
Understanding the Canna Life Cycle
To be successful with overwintering, it helps to understand what is happening beneath the soil. While many people refer to them as "bulbs," cannas actually grow from rhizomes. A rhizome is a thick, fleshy underground stem that stores energy and water for the plant.
During the summer, the canna uses its leaves to soak up sunlight and turn it into food. This food is sent down to the rhizomes, which grow larger and often sprout new "eyes" or buds. By the end of the season, a single rhizome planted in the spring often turns into a large, heavy clump.
In their native tropical environments, cannas grow year-round. In most of the United States, however, the freezing temperatures of winter would turn the water inside the fleshy rhizome into ice. This causes the plant cells to burst and the rhizome to rot. Overwintering is simply the process of moving those energy-filled stems to a place where they can stay dormant and protected from the frost.
Knowing Your USDA Hardiness Zone
The first step in overwintering is determining whether you actually need to dig your cannas up at all. This depends entirely on your hardiness zone map. Gardening success often comes down to matching your care routine to your local climate.
Zones 8 to 10
In these warmer regions, cannas are generally considered hardy. The ground rarely freezes deep enough to reach the rhizomes. You can usually leave them in the ground all year. Simply cut the foliage back after it turns brown in late fall and apply a light layer of mulch to keep the soil tidy.
Zone 7
This is the transition zone. In a mild winter, cannas in Zone 7 may survive in the ground if they are planted in a protected spot, such as near a south-facing wall. To give them the best chance, cut the stalks to the ground after the first frost and cover the area with 6 to 8 inches of mulch, like straw or shredded leaves. However, if you have a particularly prized tall variety, digging them up is the only way to be 100% sure they will survive a surprise deep freeze.
Zones 3 to 6
In these cooler climates, the ground freezes solid, which is fatal for tropical rhizomes. If you live in these zones, digging and storing your cannas indoors is a necessary part of your fall garden routine. This usually happens in October or November, depending on when the first frost arrives in your area.
Key Takeaway: If you live in Zone 6 or colder, you must dig up your canna rhizomes and store them indoors to keep them alive for next year.
When to Dig Your Canna Bulbs
Timing is one of the most important parts of successful overwintering. It is tempting to start cleaning up the garden as soon as the weather turns chilly, but with cannas, it is better to wait for a signal from nature.
The best time to dig up your cannas is shortly after the first "killing frost." This is a frost that is cold enough to turn the lush green leaves black or brown. Do not worry—the blackened leaves do not mean the plant is dead. Instead, this frost sends a chemical signal to the rhizomes that it is time to go dormant.
Waiting for this frost allows the plant to move as much energy as possible from the leaves down into the storage roots. If you dig them up while the leaves are still bright green and growing, the rhizomes may not have enough stored energy to last through the winter. Once the foliage has collapsed and turned dark, you have a window of about a week or two to get them out of the ground before the soil itself begins to freeze.
Tools You Will Need
Before you head out to the garden, gather a few basic tools. Having everything ready makes the process quick and easy.
- Garden fork or spade: A garden fork is often better because it is less likely to slice through the rhizomes than a sharp shovel.
- Pruning shears or a small garden saw: These are used to cut back the thick, watery stalks.
- Garden gloves: Canna stalks can be messy and slippery once frosted.
- Buckets or a wheelbarrow: To transport the heavy clumps to your cleaning station.
- Labels and a waterproof marker: This is vital if you grow different colors or heights of cannas and want to know which is which next spring.
Step-by-Step Guide to Digging and Cleaning
Once the frost has blackened the leaves, follow these steps to move your cannas from the soil to storage.
Step 1: Cut Back the Stalks
Start by cutting the stalks down to about 4 to 6 inches above the soil line. Leaving a few inches of the stem provides a "handle" for you to grab while you are digging. It also helps you see exactly where the center of the clump is so you do not accidentally stab it with your fork. Dispose of the blackened foliage in your compost pile or green waste bin.
Step 2: Lift the Clumps
Cannas have relatively shallow root systems, but they can spread out wide. Position your garden fork about 6 to 10 inches away from the base of the stems. Push the fork straight down into the soil and gently pry upward. Work your way around the entire circle of the plant, loosening the soil as you go. Once the soil is loose, you should be able to lift the entire heavy clump out of the ground.
Step 3: Remove Excess Soil
Gently shake the clump to remove large chunks of dirt. You can use your hands to brush away loose soil, but do not worry about getting them perfectly clean just yet.
A common question is whether you should wash canna rhizomes with a hose. For most gardeners, the answer is no. Adding extra water to the rhizomes right before you put them into storage can encourage rot or mold. It is better to let the soil dry slightly and then brush it off. The only exception is if your cannas were growing in a very muddy or bog-like area; in that case, a quick rinse to remove thick muck is okay, provided you let them dry thoroughly afterward.
Step 4: Inspect for Health
Take a close look at the rhizomes as you clean them. Healthy rhizomes should feel firm, like a fresh ginger root or a potato. If you find any parts that are mushy, slimy, or have a foul smell, those are signs of rot. Use a clean knife to cut away any damaged sections until you see clean, white flesh. If an entire clump is soft and dark throughout, it is best to discard it.
Step 5: Label Your Plants
It is easy to think you will remember which clump was the tall red one and which was the short yellow one, but by spring, all rhizomes look remarkably similar. Use a waterproof marker to write the variety name directly on the fleshy part of the rhizome, or tie a plastic tag to the remaining stem.
What to do next:
- Cut stalks to 4-6 inches.
- Lift clumps carefully with a garden fork.
- Shake off loose soil but avoid washing with water.
- Discard any mushy or rotting sections immediately.
The Importance of Curing
Before you pack your cannas away for the winter, they need to "cure." Curing is simply a fancy word for letting the outer skin of the rhizome dry and toughen up. This process helps prevent the plant from losing too much moisture during the winter and creates a barrier against fungus.
Place your cleaned rhizomes in a dry, frost-free area for one to two days. A garage, shed, or covered porch works well. Avoid placing them in direct, hot sunlight, as this can shrivel the "eyes" that will become next year's growth. You want the surface of the rhizome to feel dry to the touch and any cut ends to develop a callous.
Dividing Canna Rhizomes
You can choose to store your canna rhizomes in the large clumps you dug up, or you can divide them in the fall. Dividing them now saves space in your storage containers and makes spring planting much faster.
To divide a canna, look for the natural "nodes" or segments. Each new section you cut needs at least one or two "eyes." These eyes look like small, rounded bumps or points, similar to the eyes on a potato. You can usually snap the rhizomes apart with your hands, or use a clean, sharp knife for a more precise cut.
If you make fresh cuts, let those pieces cure for an extra day to ensure the cut surface is dry before packing them away. Dividing your cannas every year or two is the best way to expand your garden for free, as these plants are naturally vigorous growers.
Choosing the Right Storage Method
There are several ways to store canna bulbs, and the best one for you often depends on what supplies you have on hand and how much space is available. We recommend using a method that balances moisture—you want the rhizomes to stay hydrated enough that they don't turn into brittle sticks, but dry enough that they don't rot.
The Bin and Peat Moss Method
This is the most popular and reliable method. Find a sturdy plastic bin, a cardboard box, or a wooden crate.
- Place a 2-inch layer of slightly damp peat moss, perlite, or vermiculite at the bottom of the container.
- Lay the rhizomes on top of the layer, making sure they are not touching each other.
- Cover them with another layer of your chosen material.
- Repeat this until the container is full, ending with a layer of peat moss on top.
- If using a plastic bin, do not put the lid on tight. Leave it cracked or drill holes in the sides to allow for some air circulation.
The Paper Bag Method
If you only have a few cannas, paper grocery bags work well. Place the rhizomes inside the bag and fill the gaps with shredded newspaper or dry wood shavings. Fold the top of the bag over loosely. The paper allows the plants to breathe while the shavings provide a bit of insulation against temperature swings.
The Plastic Bag Method
Some gardeners prefer using large plastic trash bags. If you choose this route, it is vital to poke dozens of holes in the bag with a pen or scissors. Without these holes, moisture will trap inside, and your cannas will likely rot within weeks. Add a few handfuls of peat moss to the bag to help regulate the humidity.
Finding the Best Storage Location
Where you put your containers is just as important as how you pack them. Cannas need a spot that is "just right"—not too hot and not too cold.
The ideal temperature for storing canna rhizomes is between 45°F and 55°F. If the temperature stays consistently above 60°F, the plants may think it is spring and start to sprout prematurely in the dark. If the temperature drops below freezing, the rhizomes will die.
Excellent storage locations include:
- An unheated basement
- A crawl space
- An insulated garage that stays above freezing
- A cool closet in a mudroom
Avoid storing them in a shed or an uninsulated attic, as these areas often get far too cold in the middle of winter.
Mid-Winter Checkups
Overwintering is not a "set it and forget it" task. It is a good idea to check on your stored cannas about once a month. This small effort can save your entire collection if something starts to go wrong.
When you check them, look for two things: rot and shriveling.
- If you see rot: If a rhizome looks fuzzy with mold or feels mushy, remove it immediately. Mold can spread quickly from one plant to another. If the rot is only on a small tip, cut it off and leave the healthy portion out to dry for a day before putting it back.
- If you see shriveling: If the rhizomes look very wrinkled and feel light or brittle, they are losing too much moisture. Use a spray bottle to lightly mist the peat moss or packing material. You don't want it wet—just slightly damp to the touch.
Waking Them Up in Spring
As the days get longer and the ground begins to thaw, it’s time to think about when to plant cannas. You have two options: planting them directly in the garden or giving them a head start indoors.
Direct Planting
You can plant your saved rhizomes directly into the garden once the soil has warmed up to at least 60°F and there is no longer any danger of frost. In most regions, this is the same time you would plant tomatoes or peppers. For more detail, see our planting depth guide for canna rhizomes.
Starting Indoors (Potting Up)
For earlier blooms, many gardeners like to wake up their cannas indoors 4 to 6 weeks before the last frost, and summer-blooming bulbs for containers are a good fit.
- Choose a pot that is slightly larger than the rhizome.
- Fill the pot with high-quality potting soil.
- Plant the rhizome 2 inches deep and water it once.
- Place the pot in a warm, sunny window or under grow lights.
- Once the plant has a few leaves and the outdoor weather is warm, "harden it off" by placing it outside for a few hours a day before transplanting it into the garden.
Starting them early is particularly helpful if you live in a northern zone with a short growing season. It gives the plants a jump-start so you can enjoy flowers in early summer rather than late August.
Success with Different Canna Varieties
Most canna varieties follow these same rules. Whether you are growing a tall, heirloom Canna indica or a modern medium variety with variegated leaves, the overwintering process remains the same.
At Longfield Gardens, we have found that the larger, thicker rhizomes of tall varieties tend to be a bit more resilient in storage than the thinner rhizomes of some smaller cultivars. If you are a beginner, starting with classic green or bronze-leafed varieties is a great way to build your confidence before moving on to more delicate or rare types.
Simple Tips for Healthy Rhizomes
Gardening doesn't have to be complicated. If you focus on a few key basics, your cannas will thrive.
- Drainage is key: When you replant in the spring, ensure your soil is well-draining. Canna rhizomes love water during the heat of summer, but they hate sitting in stagnant, soggy soil, which can cause them to rot before they even start growing.
- Don't rush the spring: It is tempting to plant as soon as the first warm day hits in April. However, cannas are truly tropical. Cold, damp soil in early spring is their enemy. Waiting until the soil is truly warm will actually result in faster growth and a healthier plant.
- Feed them well: Because cannas grow so much foliage in a single season, they are hungry plants. Adding a bit of compost or a balanced fertilizer to the planting hole in the spring will give the rhizomes the fuel they need to produce those massive leaves.
Conclusion
Overwintering canna bulbs is one of the most satisfying "easy wins" in gardening. It allows you to take a beautiful tropical plant and turn it into a permanent part of your landscape, regardless of how cold your winters get. By waiting for the first frost, cleaning the rhizomes carefully, and providing a cool, dark place for them to rest, you ensure a spectacular show for the following summer.
At Longfield Gardens, we believe that gardening should be a rewarding and enjoyable journey. Saving your own plants is a wonderful way to connect with the cycle of the seasons and see the direct results of your care.
- Wait for the first frost to signal dormancy.
- Cure the rhizomes for 24-48 hours before packing.
- Store in a cool (45-55°F), dark location.
- Check monthly for rot or excessive drying.
The extra effort you put into storing your cannas this fall will be repaid tenfold when those first vibrant sprouts poke through the soil next spring, ready to transform your garden once again.
FAQ
Can I leave cannas in the ground in Zone 7?
In Zone 7, cannas can sometimes survive the winter if they are planted in a protected microclimate, such as near a warm house foundation. To give them the best chance, you must apply a very thick layer of mulch (6–8 inches) to insulate the soil. However, digging them up is still the safest way to ensure they return, especially if a particularly harsh winter occurs.
Should I wash the dirt off the bulbs before storing?
Generally, it is better to avoid washing canna rhizomes with water before storage. Excess moisture can encourage fungal growth and rot while the plants are in their containers. It is better to let the soil dry slightly and then gently brush it off with your hands or a soft brush.
What if my canna bulbs look shriveled in the spring?
It is normal for rhizomes to look a bit wrinkled or "sad" after a few months in storage. As long as they are still firm and not brittle or hollow, they are likely healthy. You can soak shriveled rhizomes in a bucket of room-temperature water for a few hours before planting to help rehydrate them and jump-start their growth.
Can I store canna bulbs in a refrigerator?
While a refrigerator provides the cool temperatures cannas need, it is usually not the best choice because it lacks airflow and can be too humid or too dry. Additionally, some fruits and vegetables in the fridge release ethylene gas, which can damage the dormant buds on the rhizomes. A cool basement or garage is almost always a better option.