Table of Contents
- Introduction
- Knowing When to Harvest Canna Bulbs
- Step-by-Step Guide to Digging Canna Rhizomes
- Cleaning and Preparing the Rhizomes
- Choosing the Right Storage Method
- Caring for Potted Cannas in Winter
- Mid-Winter Maintenance and Checks
- Preparing for Spring Replanting
- Conclusion
- FAQ
Introduction
There is a unique sense of satisfaction that comes from watching canna lilies reach their full, tropical height during the summer. Their bold leaves and vibrant blooms bring an exotic energy to the garden that is hard to match. At Longfield Gardens, we enjoy helping home gardeners bring this beauty to their yards, whether you are growing tall, dramatic varieties or compact, colorful ones.
Harvesting canna bulbs, which are technically known as rhizomes, is a rewarding autumn ritual. It allows you to save your favorite plants from year to year, ensuring your garden remains a lush sanctuary every summer. This guide is for any gardener who wants to learn the simple steps to lift, clean, and store cannas for the winter.
By following a few basic steps, you can keep your cannas healthy and ready for replanting in the spring. Transitioning your garden from the heat of summer to the quiet of winter is an achievable goal for gardeners of any skill level.
Knowing When to Harvest Canna Bulbs
The best time to harvest canna bulbs is largely determined by the weather in your specific area. In most parts of the United States, cannas are treated as tender perennials. This means they love the warmth of summer but cannot survive the freezing temperatures of a typical northern winter.
The Signal from the First Frost
Wait for the first light frost of the season before you reach for your shovel. You will know it has happened when the lush green foliage of your cannas turns brown, black, or limp overnight. While it might look disappointing to see your beautiful plants wilt, this is actually a helpful signal from nature.
When the leaves are hit by frost, the plant stops putting energy into foliage and begins to move its remaining nutrients down into the rhizome. This process helps the bulb stay strong throughout its dormant period. It is best to dig them up shortly after this first frost but before the ground freezes solid. A deep freeze can penetrate the soil and damage the tender rhizomes, so timing is everything.
Understanding Your Hardiness Zone
Your location determines whether you need to harvest your cannas at all. We suggest checking the USDA Plant Hardiness Zone Map to find your zone.
- Zones 8 to 10: In these warmer regions, cannas can often stay in the ground all year. The soil rarely freezes deep enough to damage the rhizomes. You can simply cut the foliage back and let them rest.
- Zone 7: This is a "middle ground" zone. In many years, cannas survive with a thick layer of mulch for insulation. However, if a particularly cold winter is predicted, harvesting them is the safer choice.
- Zones 3 to 6: In these colder climates, canna rhizomes will likely rot or freeze if left outdoors. For gardeners in these areas, harvesting is a necessary step to enjoy the same plants next year.
Key Takeaway: The first frost is your cue. Once the leaves turn dark and wilted, the plant is ready to be moved into storage for its winter nap.
Step-by-Step Guide to Digging Canna Rhizomes
Once the frost has arrived, you can set aside a cool, dry afternoon for harvesting. The process is straightforward and does not require specialized equipment.
Preparation and Tools
Before you head outside, gather a few basic tools. A sturdy garden spade or a garden fork is usually the best choice for lifting the heavy clumps. A garden fork is particularly helpful because it allows you to loosen the soil without cutting into the fleshy rhizomes as easily as a flat shovel might.
You may also want a pair of sharp garden pruners or a small garden saw. Canna stems are thick and fibrous, so a clean cut is easier with a sharp blade. Wear a pair of comfortable gloves to protect your hands while you work with the soil and the heavy roots.
Cutting Back the Foliage
The first physical step in harvesting is removing the spent foliage. Use your pruners to cut the stems back so they are only about 2 to 6 inches above the soil line.
Leaving a few inches of the stem attached serves a practical purpose. It acts as a convenient "handle" when you are lifting the clumps out of the dirt. It also helps you identify which end of the rhizome is the "top" when it comes time to replant them in the spring. Once the tops are removed, you can add the healthy green material to your compost pile, provided there are no signs of disease or pests.
Lifting the Clumps Safely
Canna rhizomes grow horizontally and can spread quite a bit over a single growing season. One small bulb planted in May can easily turn into a large, heavy mass by October.
To lift them safely:
- Start by inserting your spade or fork into the soil about 12 inches away from the base of the stems.
- Dig straight down and gently pry upward to loosen the soil around the entire perimeter of the plant.
- Slowly work your way around the clump, loosening it from all sides.
- Once the soil is loose, use the stem handles 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 the mass while it is still in the ground. Just be sure to leave plenty of space around the main growth points.
What to Do Next
- Check the weather forecast for a dry window of time.
- Cut stems to a manageable 4-inch height.
- Loosen the soil in a wide circle to avoid piercing the roots.
- Gently lift the rhizomes and shake off the heaviest clods of dirt.
Cleaning and Preparing the Rhizomes
Once the rhizomes are out of the ground, they need a little bit of cleaning and "curing" before they go into long-term storage. This part of the process ensures they stay healthy and do not develop rot while they are tucked away in your basement or garage.
Removing Excess Soil
Use your hands to gently brush away the loose soil clinging to the rhizomes. You do not need to make them perfectly clean. In fact, a little bit of remaining soil can sometimes help prevent the rhizome from drying out too quickly.
Some gardeners prefer to wash their canna bulbs with a garden hose. If you choose to do this, use a gentle stream of water. Avoid high-pressure nozzles that could tear the "skin" of the rhizome. If you do wash them, it is vital that you allow them to dry completely before moving to the next step. Moisture is the biggest enemy of successful winter storage.
Curing for Better Storage
Curing is simply a fancy word for letting the rhizomes air-dry for a short period. Find a protected, dry spot like a garage, shed, or a covered porch. Lay the rhizomes out in a single layer on a piece of cardboard or a newspaper.
Let them sit for 24 to 48 hours. This allows the outer skin to toughen up and any remaining soil to dry out. It also gives any small wounds or cuts from the digging process a chance to "callous" over. A calloused wound is much less likely to invite fungus or rot than a fresh, wet cut.
How to Divide Canna Rhizomes
Fall is a great time to divide your cannas, especially if the clumps have become unmanageably large. However, you can also wait until spring if you prefer.
When dividing, look for the "eyes." These are the small, rounded bumps on the rhizome where new growth will emerge. A healthy division should have at least two or three of these eyes. You can usually snap the rhizomes apart by hand, or use a clean, sharp knife for a more precise cut. If you use a knife, some gardeners like to dust the fresh cuts with a little bit of sulfur powder to prevent mold, though this is not strictly necessary if your storage area is dry.
Key Takeaway: Clean away the bulk of the dirt, but don't worry about every speck. The most important part is letting the rhizomes dry for a day or two so they stay firm and healthy.
Choosing the Right Storage Method
The goal of winter storage is to keep the rhizomes in a state of suspended animation. You want them to stay cool enough that they do not start growing, but warm enough that they do not freeze. You also want to maintain a balance of moisture—they shouldn't be so wet that they rot, but they shouldn't be so dry that they shrivel up into hard sticks.
Using Peat Moss and Vermiculite
One of the most reliable ways to store canna bulbs is by packing them in a slightly moisture-retentive medium.
- Peat Moss: This is the most common choice. It is lightweight and helps maintain a steady environment.
- Vermiculite or Perlite: These are also excellent options as they provide good insulation and help regulate moisture.
- Wood Shavings: Clean, dry sawdust or cedar shavings can work well too.
Place a layer of your chosen material in the bottom of a container. Lay the rhizomes on top, making sure they are not touching each other. Then, cover them with more of the material. This "sandwich" technique prevents rot from spreading if one bulb happens to go bad.
Containers: Newspaper and Paper Bags
We recommend using containers that can "breathe." Cardboard boxes, paper grocery bags, or even plastic bins with the lids left off (or with holes drilled in the sides) are ideal. Avoid sealing cannas in airtight plastic bags or containers, as this traps moisture and almost always leads to mold.
If you are short on space, you can also wrap individual rhizomes in several layers of newspaper. This is a simple, low-cost method that provides a good buffer against temperature swings.
Ideal Temperature and Humidity
The perfect spot for your stored cannas is somewhere dark and cool. A temperature range of 40°F to 50°F is the "sweet spot."
- Unheated Basements: Usually provide the most consistent temperatures.
- Crawl Spaces: These are often ideal if they stay above freezing.
- Attached Garages: Can work, but be careful of areas near the door where temperatures might drop too low on a very cold night.
Avoid storing them near a furnace or water heater, as the dry heat will cause the rhizomes to desiccate (dry out) too quickly.
What to Do Next
- Select a breathable container like a cardboard box.
- Line the bottom with 2 inches of peat moss or shredded paper.
- Arrange rhizomes so they are not touching.
- Place the box in a cool, dark corner away from direct heat.
Caring for Potted Cannas in Winter
If you grow your cannas in large decorative pots, you have a shortcut available. You do not necessarily have to dig the rhizomes out of the soil.
Once the first frost hits and you have cut back the foliage, simply move the entire pot into a cool, frost-free area like a basement or garage. Stop watering the pot entirely. The soil in the pot will dry out, and the plant will go dormant right where it is.
In the spring, about a month before the last frost, you can bring the pot back into the light, give it a good soak, and wait for the new shoots to appear. If the pot has become "root-bound" (meaning the roots are packed too tightly), you can tip it over, divide the rhizomes, and replant them with fresh potting soil.
Mid-Winter Maintenance and Checks
One of the most helpful tips we can offer at Longfield Gardens is to check on your stored bulbs at least once or twice during the winter. Even with perfect preparation, the environment can change.
Identifying Problems Early
Set a reminder on your calendar for January and February. Open your storage boxes and take a quick look.
- Check for Rot: If a rhizome feels soft, mushy, or has a bad odor, it is starting to rot. Remove it immediately and throw it away so it doesn't infect its neighbors.
- Check for Shriveling: If the rhizomes feel very light and look extremely wrinkled, they might be getting too dry. You can give them a very light misting of water with a spray bottle. You don't want them wet; you just want to add a tiny hint of humidity to the packing material.
Handling Mold
If you see a small amount of surface mold but the rhizome is still firm, you can usually save it. Simply wipe the mold off with a dry cloth and move the box to a spot with slightly better air circulation. This is a common occurrence and usually means the storage medium was just a little too damp.
Preparing for Spring Replanting
As the days get longer and the ground begins to thaw, your canna rhizomes will start to wake up. You might even see small white or pink "pips" (new growth) starting to emerge from the eyes while they are still in their boxes.
Timing the Return to the Garden
Do not be in a rush to plant cannas back in the ground. They are tropical plants that love warm soil. We suggest waiting until the danger of frost has completely passed and the soil has warmed up to at least 60°F. In most regions, this is around the same time you would plant tomatoes or peppers.
Starting Them Early Indoors
If you want to enjoy flowers earlier in the season, you can plant canna lily bulbs indoors about 4 to 6 weeks before the last frost date. Place them in a pot with some moist potting soil and keep them in a warm, sunny window. By the time the outdoor weather is right, you will have a well-established plant ready to take off.
Key Takeaway: Patience is a virtue with cannas. Waiting for warm soil ensures the rhizomes grow vigorously rather than sitting in cold, damp earth.
Conclusion
Harvesting and storing canna bulbs is one of the most rewarding ways to practice sustainable gardening. It turns a one-season plant into a multi-year investment, allowing you to build a larger and more impressive display each summer. By paying attention to the first frost and providing a cool, dry home for your rhizomes, you ensure that your garden will be ready to glow with tropical color once the warmth of spring returns.
At Longfield Gardens, we believe that these simple steps make gardening accessible and enjoyable for everyone. There is something truly special about holding a dormant rhizome in your hand during the winter and knowing the vibrant life that is waiting inside it.
- Wait for the first frost to turn the leaves brown before digging.
- Dry and cure the rhizomes for 48 hours to prevent rot.
- Store in a breathable container with peat moss or newspaper.
- Keep the storage area cool (40-50°F) and dark.
"The cycle of harvesting and replanting connects us to the seasons, making the eventual return of summer blooms even more satisfying."
We look forward to seeing your garden thrive. If you are looking to add premium canna varieties and other summer-blooming favorites to your collection, feel free to explore our selection.
FAQ
Should I wash my canna rhizomes before storing them?
While you can wash them, it isn't strictly necessary. It is often safer to simply brush off the loose soil. If you do wash them, you must ensure they are 100% dry before putting them into storage, as any trapped water can lead to mold and rot over the winter months.
What if I don't have a basement or a garage for storage?
Any cool, dark spot that stays between 40°F and 50°F will work. This could be a crawl space, a cool closet on an outside wall, or even a protected corner of an apartment balcony if you use an insulated cooler. The key is preventing the rhizomes from freezing while keeping them dormant.
My canna rhizomes look very shriveled in mid-winter. Are they dead?
Not necessarily. Rhizomes naturally lose some moisture during dormancy. If they are still firm when you squeeze them, they are likely just fine. If they feel extremely light and brittle like a dry twig, you can lightly mist their storage medium with water to help them rehydrate slightly.
Can I leave cannas in the ground if I live in Zone 7?
In Zone 7, it is often a gamble. During a mild winter, cannas can survive if they are covered with 6 to 8 inches of mulch, such as straw or shredded leaves. However, if your area experiences a "polar vortex" or a prolonged deep freeze, the rhizomes may not survive, so many gardeners in Zone 7 choose to dig up a few "backups" just in case.