Are Canna Lilies Bulbs Or Tubers? The Simple Answer

Table of Contents

1. Introduction
2. Defining the Terms: Bulbs, Tubers, and Rhizomes
3. Why the Rhizome Structure Matters for Planting
4. The Role of Temperature and Timing
5. Watering and Soil Requirements
6. Overwintering: Managing Rhizomes in Cold Climates
7. How to Divide Canna Rhizomes
8. Cannas in Containers
9. Common Myths About Canna Roots
10. Growing with Confidence
11. Conclusion
12. FAQ

Introduction

There is nothing quite like the sight of a canna lily in full mid-summer glory. With their towering stalks, lush tropical leaves, and vibrant blooms in shades of red, orange, and yellow, tall cannas bring an undeniable energy to any backyard. Whether you are looking to create a backyard oasis or just want to add some height to your flower beds, these plants are a fantastic choice for gardeners of all skill levels.

When you prepare to plant these beauties, you might find yourself wondering exactly what you are holding in your hand. In the gardening world, we often use the term "bulb" as a catch-all for anything planted underground that stores energy. However, if you look closely at the root of a canna, you will notice it looks quite different from a round tulip bulb or a lumpy dahlia tuber.

At Longfield Gardens, we want to help you understand the science behind your plants so you can provide the best possible care. Understanding whether a plant is a bulb, a tuber, or something else entirely changes how you plant it, how you water it, and how you store it over the winter. Our All About Cannas guide will clarify the biology of the canna lily and give you the practical steps needed for a successful growing season.

The short answer is that canna lilies are neither true bulbs nor true tubers; they are actually rhizomes. This distinction is the key to unlocking their growth potential and ensuring they return to your garden year after year.

Defining the Terms: Bulbs, Tubers, and Rhizomes

To understand why a canna lily is a rhizome, it helps to look at the differences between the various types of underground storage organs. Gardeners often group these together under the name "geophytes." A geophyte is simply a plant that has a specialized part underground where it stores food, water, and energy to survive through periods of dormancy.

What Is a True Bulb?

A true bulb is a complete, miniature plant packed inside a protective fleshy structure. If you cut a true bulb in half, like an onion or a tulip, you will see layers of scales. These scales are actually modified leaves that store food. At the very center is a tiny flower bud waiting for the right temperature to emerge. True bulbs usually have a pointed top where the sprout comes out and a flat "basal plate" at the bottom where roots grow.

What Is a Tuber?

A tuber is a thickened part of an underground stem or root. Unlike a true bulb, a tuber does not have layers or a protective skin. Potatoes and dahlias are the most common examples of tubers. Tubers have "eyes" or growth nodes scattered across their surface. Each of these eyes can potentially produce a new sprout. Because they are basically solid storage tanks of starch, they can be quite irregular in shape.

What Is a Rhizome?

A rhizome is a fleshy, horizontal stem that grows just beneath or even right at the soil surface. Instead of growing straight down like a root, it travels sideways. As it moves through the soil, it sends out roots from its bottom and shoots from its top.

Canna lilies fit perfectly into this category. If you look at a canna root, you will see it is long and segmented, often looking a bit like a piece of ginger. It grows horizontally and has distinct nodes or "eyes" along the segments. This horizontal growth is why cannas tend to spread and form thick, beautiful clumps over time.

Key Takeaway: While we often call them bulbs for convenience, canna lilies are botanically rhizomes. They are horizontal stems that store energy and spread sideways through the soil.

Why the Rhizome Structure Matters for Planting

Knowing that a canna is a rhizome changes how you place it in the ground. Because rhizomes grow horizontally, they need a bit more "elbow room" in the soil compared to a vertical bulb like a lily.

Planting Direction

When you plant a tulip bulb, you always put the pointy end up. With a canna rhizome, the orientation is different. You should lay the rhizome on its side, horizontally. Look for the "eyes" or small, pointed bumps on the surface. These are the growth points. Ideally, you want these eyes to be facing upward or toward the side. If you aren't sure which way is up, don't worry. The plant is very smart and will eventually find its way toward the sunlight, but laying it flat gives it the best head start. For a bold, upright look, try Canna Tall Tropicanna.

Planting Depth

Rhizomes do not like to be buried too deeply. In nature, many rhizomes sit very close to the soil surface to catch the warmth of the sun. For cannas, a depth of about 4 to 5 inches is usually perfect. This provides enough soil cover to keep the plant stable as it grows tall, but it is shallow enough that the soil can warm up quickly in the spring.

Spacing for Success

Since canna rhizomes grow outward, they need space to expand. If you plant them too close together, they will compete for nutrients and water, which can lead to smaller flowers. We recommend spacing large canna varieties about 1 to 2 feet apart. This gives the rhizomes room to creep and create a dense, lush screen of foliage without crowding their neighbors. For a smaller footprint, Short Cannas are a good fit.

What to Do Next:

• Identify the "eyes" on your canna rhizome before planting.
• Dig a shallow trench rather than a deep hole.
• Lay the rhizome horizontally in the soil.
• Space multiple plants at least 18 inches apart to allow for spreading.

The Role of Temperature and Timing

Because cannas are tropical plants, their rhizomes are very sensitive to cold. This is one of the most important things to remember when working with rhizomes instead of hardy bulbs like daffodils.

True bulbs often need a period of cold (winter) to trigger their blooming cycle. Canna rhizomes are the opposite. They crave heat. They will stay dormant until the soil temperature reaches a consistent 60°F or higher. If you plant them in cold, wet soil too early in the spring, the rhizome may sit idle or, in some cases, rot before it has a chance to wake up.

Waiting for the Right Moment

The best time to plant your canna rhizomes is after the danger of frost has passed and the soil has warmed up. In many parts of the United States, this is usually in May or early June. A simple way to check is to feel the soil with your bare hand; if it feels cold to the touch, it is probably too early.

If you live in a region with a short growing season, you can give your cannas a head start. About 4 to 6 weeks before the last frost, plant the rhizomes in pots indoors. Place the pots in a warm, sunny window. By the time the weather warms up outside, you will have established plants ready to be moved into the garden. This "pre-starting" method often results in earlier blooms.

Sunlight and Energy Storage

Rhizomes are energy storage units. To fill those units for the following year, the plant needs plenty of fuel. For cannas, that fuel is sunlight. They perform best in full sun, which means at least 6 to 8 hours of direct light each day. The more sun they get, the more energy the rhizome can store, and the bigger your flowers will be. Canna Tall Australia is a striking sun-lover with dark foliage and bright flowers.

Watering and Soil Requirements

The physical structure of a rhizome also dictates how the plant interacts with water. Because rhizomes are fleshy and hold a lot of moisture, they are susceptible to "wet feet" if the soil does not drain well.

Understanding Drainage

"Drainage" is a term gardeners use to describe how fast water leaves the soil. If you pour water on a spot and it stays in a puddle for an hour, that soil has poor drainage. If the water disappears into the ground almost immediately, it has good drainage.

Cannas love water, but they don't like to sit in stagnant, soggy earth. The best soil for cannas is rich in organic matter but loose enough to let excess moisture move through. If you have heavy clay soil, you can improve it by adding compost or peat moss, which helps create air pockets and better flow.

Water Deeply, Not Constantly

When your cannas are actively growing, they are thirsty plants. The large leaves lose a lot of moisture through evaporation on hot days. However, instead of giving them a light sprinkle every day, it is better to water them deeply once or twice a week. This encourages the roots to grow deeper into the soil, making the plant more resilient and healthy.

During the heat of mid-summer, check the soil moisture by sticking your finger an inch or two into the ground. If it feels dry, it’s time for a drink. If you are growing cannas in containers, keep in mind that pots dry out much faster than the ground, so you may need to water them more frequently. Canna Medium Banana Punch is a lively choice for a pot.

Overwintering: Managing Rhizomes in Cold Climates

One of the most common questions we hear is whether canna lilies can stay in the ground all year. The answer depends entirely on your USDA hardiness zone.

Cannas are hardy in zones 8 through 11. In these warm regions, you can usually leave the rhizomes in the ground year-round. You can simply cut the foliage back after it turns brown and perhaps add a layer of mulch for extra protection. However, for gardeners in zones 7 and colder, the winter freeze will likely kill the rhizome if it is left unprotected.

When to Dig Them Up

If you live in a cold climate, you should treat your cannas as "tender" plants. This means you need to lift the rhizomes from the soil and store them indoors for the winter. For step-by-step help, see How to Divide and Store Canna Bulbs for Winter.

The best time to do this is right after the first light frost. You will notice the leaves turn black or wilted once the frost hits. This is the plant's signal that it is time to go dormant. Don't worry—the frost that kills the leaves won't hurt the rhizomes underground as long as the ground itself hasn't frozen yet.

The Lifting Process

1. Cut back the stalks: Use garden shears to cut the stems down to about 2 to 4 inches above the soil.
2. Dig carefully: Use a garden fork or a shovel to gently loosen the soil around the clump. Start about a foot away from the base of the plant to avoid slicing into the rhizomes.
3. Lift and clean: Gently lift the clump out of the ground. Shake off the excess soil. You can rinse them with a hose if you want them very clean, but it isn't strictly necessary.
4. Cure the rhizomes: Let the rhizomes sit in a dry, shaded area (like a garage or porch) for a few days. This "curing" process helps the outer skin toughen up, which prevents rot during storage.

Storing for the Winter

Once the rhizomes are dry to the touch, you need to keep them in a "goldilocks" environment: not too cold, not too hot, and not too dry.

Place the rhizomes in a box or a breathable bag filled with peat moss, sawdust, or wood shavings. These materials help maintain a consistent moisture level. You don't want the rhizomes to shrivel up like raisins, but you also don't want them to be damp, which causes mold.

Store the box in a cool, dark place that stays between 40°F and 50°F. An unheated basement, a crawl space, or a cool closet usually works well. Check on them once a month. If they look wrinkled, give the packing material a very light mist of water. If you see any soft or mushy spots, remove those pieces immediately so the rot doesn't spread.

Key Takeaway: In cold zones, canna rhizomes must be lifted after the first frost and stored in a cool, dry place to survive until spring.

How to Divide Canna Rhizomes

One of the most rewarding things about canna lilies is that they are the gift that keeps on giving. Because rhizomes grow and spread horizontally, a single plant can turn into a large clump in just one or two seasons. To keep the plants healthy and to get more flowers for your garden, you can divide these clumps.

The Best Time to Divide

The ideal time to divide canna rhizomes is in the spring, just before you plant them. This allows you to see where the new growth points (the eyes) are emerging. You can also divide them in the fall when you dig them up for storage, but many gardeners prefer waiting until spring to see which parts of the rhizome survived the winter best.

Step-by-Step Division

1. Inspect the clump: Look for natural breaking points in the rhizome.
2. Ensure eyes are present: For a division to grow into a new plant, it must have at least one "eye" or sprout. Ideally, each piece should have two or three eyes to ensure a strong, bushy plant.
3. Make the cut: You can often snap the rhizomes apart with your hands, or you can use a clean, sharp knife.
4. Let them dry: If you make a fresh cut, let the piece sit out for a day so the "wound" can callus over. This protects the plant from soil-borne diseases.

By dividing your cannas every 2 to 3 years, you prevent the center of the clump from becoming overcrowded and "spent." Plus, you'll have extra plants to share with neighbors or to start a new flower bed in another part of your yard. A classic like Canna Medium Cleopatra can be divided this way as it matures.

Cannas in Containers

If you don't have a lot of garden space, or if you want to avoid the task of digging up rhizomes from the ground every autumn, growing cannas in containers is a perfect solution. Because they are rhizomes, they adapt very well to pot life as long as the pot is big enough.

Choosing the Right Pot

A standard canna lily can grow quite large, so you will need a heavy, stable pot to prevent it from tipping over in the wind. A 12-inch diameter pot is usually sufficient for one rhizome, while a larger 18-inch pot can hold two or three. Ensure the pot has drainage holes at the bottom so water can escape. For more potting basics, see How to Grow Summer Bulbs in Containers.

Potting Mix

Use a high-quality potting soil rather than garden soil. Potting soil is designed to be lightweight and well-draining, which is exactly what a rhizome needs to thrive. You can mix in a little slow-release fertilizer at planting time to provide a steady supply of nutrients throughout the summer.

Container Care

Cannas in pots need more frequent watering and fertilizing than those in the ground. Because the rhizome is confined to a small space, it will quickly use up the available water and nutrients. During the peak of summer, you might find yourself watering your container cannas every day. Canna Short Pink Magic is a compact choice that works well in a 12-inch pot.

When winter approaches, container gardening makes storage a breeze. Once the first frost hits, simply cut back the foliage and move the entire pot into a cool, frost-free area like a garage. You don't even have to dig the rhizomes out of the dirt; just let them sleep in the pot until spring. Another compact option is Canna Short Orange Chocolate.

Common Myths About Canna Roots

Because the terminology can be confusing, there are a few common myths that we often encounter. Let's clear those up to make your gardening experience even easier.

Myth 1: You have to plant cannas very deep to keep them from falling over. While cannas can grow 6 feet tall, planting the rhizome 12 inches deep will only delay its growth and potentially cause it to rot. A depth of 4 to 5 inches is plenty. The weight of the soil and the spread of the roots will provide all the stability the plant needs. If you live in a very windy area, you can use a simple bamboo stake for extra support.

Myth 2: If the rhizome feels light, it is dead. A healthy rhizome should feel firm and relatively heavy for its size, similar to a fresh potato. If a rhizome feels as light as a feather or squishes when you touch it, it has likely dried out completely or rotted. However, some surface wrinkling is normal during winter storage and doesn't necessarily mean the plant is gone.

Myth 3: You need special chemicals to make them bloom. Cannas are actually very low-maintenance. They don't need "magic" fertilizers. Their ability to bloom comes from the energy stored in the rhizome. As long as you provide plenty of sun, regular water, and a bit of basic compost or flower fertilizer, they will perform beautifully. That confidence is backed by our 100% Quality Guarantee.

What to Do Next:

• Check your hardiness zone to decide if you need to dig up your rhizomes.
• In the spring, divide any large clumps to create new plants.
• Consider starting one or two cannas in pots for a portable tropical look.
• Always prioritize sun and drainage for the healthiest rhizomes.

Growing with Confidence

Gardening is a journey of discovery, and every plant has its own unique way of growing. By learning that canna lilies are rhizomes, you have already taken a big step toward becoming a more successful gardener. You now know how they spread, why they need horizontal space, and how to protect their energy stores during the cold winter months.

At Longfield Gardens, we believe that everyone can have a beautiful garden. It doesn't require a green thumb or decades of experience—it just takes a little bit of knowledge and the right plants. Canna lilies are some of the most rewarding plants you can grow, offering a massive visual impact for very little effort. Before you order, review our Shipping Information so you know when your plants will arrive.

Whether you are planting them in a dedicated border, using them as a privacy screen, or featuring them in a decorative pot on your patio, these tropical treasures will reward you with months of stunning color. Remember to keep them warm, keep them watered, and give them plenty of sunshine.

"Understanding the biology of your plants is the best way to ensure a vibrant garden. When you know how a canna rhizome works, you can work with nature instead of against it."

Conclusion

Canna lilies are a spectacular addition to any landscape, providing bold textures and brilliant colors that last from early summer until the first frost. While they are frequently called bulbs or tubers, they are technically rhizomes—underground stems that grow horizontally and store the energy needed for those magnificent blooms. By focusing on proper planting depth, horizontal orientation, and ensuring they have plenty of warmth and drainage, you can enjoy these tropical favorites year after year.

• Canna lilies are rhizomes, which are horizontal underground stems.
• Plant them 4 to 5 inches deep in a horizontal position once the soil is warm.
• In cold climates (Zone 7 and lower), dig them up after the first frost for winter storage.
• Divide the rhizomes every few years to keep the plants vigorous and to expand your garden.

We hope this guide has cleared up any confusion about these wonderful plants. If you're ready to add some tropical flair to your yard, we invite you to explore the many beautiful varieties we offer at Longfield Gardens and start planning your most colorful season yet.

FAQ

Should I soak canna rhizomes before planting?

Soaking is not strictly necessary for canna rhizomes, as they are naturally fleshy and hold a good amount of moisture. However, if your rhizomes look particularly dry or shriveled after winter storage, a short soak in lukewarm water for about two hours can help "wake them up" and rehydrate the tissues before they go into the ground.

How many eyes should a canna division have?

For the best results, each division should have at least two to three "eyes" or growth nodes. While a piece with a single eye can still grow, having multiple eyes ensures a fuller, more robust plant with more stalks and flowers in its first season. More eyes generally lead to a more stable and vigorous plant.

Can I leave cannas in the ground if I live in Zone 7?

Zone 7 is a "borderline" zone for cannas. In a mild winter, they may survive if they are planted in a protected area (like near a south-facing wall) and covered with a thick layer of mulch. However, a particularly cold or wet winter can still kill them, so many gardeners in Zone 7 choose to dig them up just to be safe. If you are unsure, check the Hardiness Zone Map.

Why are my canna rhizomes rotting in the garden?

Rot is usually caused by "wet feet," which happens when the soil doesn't drain quickly enough. If the soil is heavy clay or stays soggy for long periods, the fleshy rhizome can succumb to fungus or bacteria. To prevent this, always plant in a well-draining spot and wait until the soil is warm and the weather is consistently dry before planting in the spring.