Table of Contents
- Introduction
- The Appeal of Giant Canna Bulbs
- Choosing the Right Giant Varieties
- Finding the Best Spot for Your Cannas
- When to Plant Giant Canna Bulbs
- How to Plant Giant Canna Bulbs
- Summer Care for Maximum Height
- Grooming and Maintenance
- Managing Pests with a Positive Approach
- Giant Cannas in Different Climates
- Designing Your Garden with Giant Cannas
- Realistic Expectations for Growth
- Conclusion
- FAQ
Introduction
There is a unique sense of wonder that comes with watching a garden transform from bare soil into a towering tropical oasis in a single season. Giant canna bulbs are the secret to achieving this dramatic look, offering lush foliage and vibrant blooms that can easily reach over six or eight feet tall. At Longfield Gardens, we enjoy how these architectural plants provide an instant sense of privacy and a bold, exotic feel to any backyard or patio.
Whether you are looking to create a living screen or want a stunning focal point for your flower beds, these easy-to-grow plants are a fantastic choice for gardeners of all experience levels. This guide will walk you through everything you need to know about selecting, planting, and caring for these impressive garden giants. By understanding a few simple basics about sun, water, and soil, you can enjoy a spectacular summer display that lasts until the first frost.
The Appeal of Giant Canna Bulbs
Most people are familiar with standard cannas, which usually grow three to four feet tall. However, giant cannas take things to a completely different level. These plants are prized as much for their massive, banana-like leaves as they are for their flowers. Some varieties focus heavily on foliage, with leaves that can be two feet long and a foot wide, while others produce pendulous or upright blossoms in shades of red, orange, and pink.
Because of their incredible growth rate, giant cannas are perfect for gardeners who want a "finished" looking garden quickly. In the heat of the summer, a healthy canna can grow several inches in a single week. This makes them ideal for new gardens where trees and shrubs haven't yet reached their full height. They fill vertical space that most other perennials simply cannot reach.
Choosing the Right Giant Varieties
When shopping for giant canna bulbs—which are technically called rhizomes—it helps to know what kind of look you want to achieve. Not all cannas grow to towering heights, so looking for specific names—or browsing Short Cannas—is the best way to ensure you get the size you expect.
Canna Musifolia
Often called the "Grande" canna, Canna musifolia is the gold standard for height. It can easily reach 8 to 10 feet tall under the right conditions. The flowers are relatively small and orange-red, but the real star is the foliage. The leaves are huge, bronze-edged, and look remarkably like a banana plant. If your goal is a tropical forest vibe, this is the variety for you.
Canna Ehemanii
This is a rare and elegant giant known for its graceful, drooping clusters of deep rose-pink flowers. Unlike the upright spikes of most cannas, Ehemanii has flowers that hang down like bells. It typically reaches 6 to 8 feet and has soft, light green leaves that feel like velvet. It provides a more sophisticated, airy look compared to the dense wall of foliage provided by other giants.
Australian and Other Bronze-Leaf Giants
Some giant varieties, like Canna Tall Tropicanna Black, offer stunning dark foliage. These plants can reach 6 feet or more and feature deep burgundy or chocolate-colored leaves. The contrast between the dark foliage and bright red or orange flowers creates a high-impact look that stands out from across the yard.
Key Takeaway: Giant cannas are selected primarily for their height and foliage. If you want a living wall, choose Musifolia. If you prefer elegant flowers at eye level, look for Ehemanii.
Finding the Best Spot for Your Cannas
To get the most height out of your giant canna bulbs, you need to match the plant’s needs to the right location in your yard. Cannas are tropical plants at heart, which means they have three main requirements: lots of sun, plenty of heat, and consistent moisture.
Sun and Heat
Giant cannas need full sun to reach their maximum potential. In most regions, this means at least six to eight hours of direct sunlight every day. If they are planted in too much shade, they will grow shorter, their stems may become weak, and they won't produce as many flowers.
Heat is the fuel that drives canna growth. These plants often sit quietly in the spring and then "explode" once the daytime temperatures consistently stay above 70°F. If you live in a cooler climate, planting them near a south-facing wall can provide extra reflected heat to help them grow faster.
Soil and Drainage
While cannas love water, they do not like to sit in stagnant, soggy soil that doesn't move. "Drainage" refers to how fast water leaves the soil after a rain or watering session. Ideally, you want soil that stays moist but allows excess water to trickle away.
If your soil is very heavy clay, you can improve it by adding organic matter like compost or aged manure. This helps create a looser structure that the thick rhizomes can easily push through. For giant varieties, rich soil is essential because it takes a lot of energy to build an eight-foot plant in just a few months.
Wind Protection
Because giant cannas grow so tall and have such large leaves, they can act like sails in the wind. A very strong gust can occasionally tatter the leaves or tip over a plant that isn't well-supported. If possible, plant your giants in a spot that has some protection from the strongest prevailing winds, such as near a fence, a hedge, or the side of a house.
When to Plant Giant Canna Bulbs
Timing is one of the most important factors for success with cannas. Because they are tender perennials, they are very sensitive to cold temperatures.
In the United States, the right time to plant depends on your local weather. A good rule of thumb is to wait until the danger of frost has completely passed and the soil has warmed up. If the soil is still cold and wet, the bulbs may sit dormant or, in rare cases, struggle to start. We recommend waiting until the soil temperature is at least 60°F. If you're ordering ahead, our Shipping Information page explains timing by zone.
For many gardeners, this timing coincides with when you would plant tomatoes or peppers. If you want a head start, you can plant your giant canna bulbs in pots indoors about four to six weeks before the last frost date. This gives them a "jump start" so they are already a few inches tall when they move outside.
How to Plant Giant Canna Bulbs
Planting cannas is a simple process, but getting the depth and spacing right will ensure your plants have the room they need to thrive.
Step 1: Prepare the Soil
Dig a hole about 6 to 8 inches deep and loosen the soil at the bottom. Mix in a handful of compost or a balanced, slow-release fertilizer. This gives the roots immediate access to the nutrients they need to start growing.
Step 2: Position the Rhizome
Look at your canna bulb (rhizome). You will see small bumps or "eyes," which are the growing points where the stems will emerge. Place the rhizome in the hole horizontally with the eyes facing upward. If you can't tell which way is up, don't worry—the plant will naturally figure out which way to grow.
Step 3: Planting Depth
Cover the rhizome with about 2 to 4 inches of soil. Planting them at this depth protects the bulb from temperature swings while making it easy for the young shoots to reach the surface. For a deeper walkthrough, see How Deep Do You Plant Canna Bulbs?.
Step 4: Spacing
Giant cannas need space to breathe and expand. If you plant them too close together, they will compete for light and water, which can limit their height. Space giant varieties 18 to 24 inches apart. This might look like a lot of empty space in the spring, but by July, the large leaves will fill that gap completely.
Step 5: Initial Watering
Water the area thoroughly right after planting to settle the soil around the bulbs. You don't need to water constantly until you see green shoots poking through the ground. Once the plant is actively growing, you can increase the frequency of watering.
What to do next:
- Check your local frost dates to time your planting.
- Enrich your planting site with compost or organic matter.
- Plant rhizomes 2-4 inches deep with eyes facing up.
- Give giant varieties at least 2 feet of space between each plant.
Summer Care for Maximum Height
Once your giant cannas are established and growing, they are relatively low-maintenance. However, a little extra attention during the peak of summer will help them reach their full "giant" potential.
Watering Regularly
Cannas are thirsty plants. Because they have such large leaves, they lose a lot of moisture through evaporation on hot days. During the heat of summer, they should be watered deeply. For a fuller schedule, see How Often to Water Canna Bulbs for Best Blooms. The goal is to keep the soil consistently moist. If you notice the edges of the leaves starting to turn brown or "burn," it is often a sign that the plant needs more water.
If you are growing giant cannas in containers, they will need even more frequent watering—sometimes every day during a heatwave. Using a large pot (at least 15-20 gallons) helps hold more moisture and provides the weight needed to keep the tall plant from tipping over.
Feeding Your Giants
Think of cannas as "heavy feeders." It takes a massive amount of energy to produce those huge leaves and thick stems. We recommend applying a balanced liquid fertilizer every two to three weeks during the growing season. Alternatively, you can use a slow-release granular fertilizer once a month. Look for a formula where the three numbers on the bag (NPK) are roughly equal, or one with a slightly higher middle number to encourage blooming.
Mulching
Applying a 2-inch layer of mulch around the base of the plants is a simple win for any gardener. For help choosing a material, see The Best Mulch for Flower Gardens. Mulch helps keep the soil cool and holds in moisture, which reduces the amount of time you spend with the garden hose. It also discourages weeds from growing and competing with your cannas for nutrients. Use natural materials like shredded bark, straw, or compost.
Grooming and Maintenance
To keep your giant cannas looking their best, a small amount of grooming goes a long way. This is not a difficult chore, but it keeps the plants looking fresh and encourages more flowers.
Deadheading
"Deadheading" is the process of removing faded flowers. Once a flower spike has finished blooming, you can cut it back to the next side bud or leaf. This prevents the plant from putting energy into producing seeds and encourages it to send up new flower spikes. With giant varieties, you may need a pair of long-handled loppers or a small step stool to reach the tops of the plants!
Removing Old Leaves
As the season progresses, the oldest leaves at the very bottom of the plant may naturally turn yellow or brown. This is normal. Simply snip them off near the main stem to keep the plant looking tidy. This also improves air circulation around the base of the plant.
Supporting Tall Stems
Most giant cannas have very thick, sturdy stems that don't require staking. However, if you live in a very windy area or if your soil is exceptionally loose, you might find that the plants lean slightly. You can use a sturdy bamboo stake and some soft garden twine to give them a little extra support if needed.
Managing Pests with a Positive Approach
Cannas are generally very healthy plants, but they do have one common visitor: the canna leafroller. These are small caterpillars that stitch the edges of a leaf together before it unfurls, creating a little tube to live in.
The best way to handle this is to keep an eye on your plants as the new leaves emerge. If you see a leaf that looks like it's being held shut by silk threads, you can simply unroll it by hand and remove the caterpillar. Keeping your plants healthy with plenty of water and fertilizer makes them much more resilient to any minor insect activity. In many cases, the plant grows so fast that a little bit of leaf damage won't even be noticeable against the backdrop of so much lush foliage.
Giant Cannas in Different Climates
How you handle your cannas at the end of the year depends on where you live. This is where understanding your USDA hardiness zone becomes helpful.
Warm Climates (Zones 8-11)
In the southern parts of the US, giant cannas are often treated as perennials. This means they can stay in the ground all year round. After the foliage dies back in the late fall or after a light frost, you can cut the stems down to about 4 inches above the ground. Apply a thick layer of mulch over the area to protect the rhizomes during the winter. They will sprout again on their own when the weather warms up in the spring.
Cold Climates (Zones 3-7)
In northern regions, giant cannas will not survive the freezing temperatures of winter if left in the ground. However, you can easily save the bulbs to plant again next year. This is a rewarding way to see your "giants" get even bigger over time, as the rhizomes grow larger each season. For the storage steps, see How to Store Canna Bulbs for Winter.
- Wait for Frost: Let the first light frost turn the foliage brown. This tells the plant to move its energy down into the bulb.
- Cut Back: Cut the stems down to about 4 to 6 inches.
- Dig Carefully: Use a garden fork to gently lift the clump of rhizomes out of the ground. Be careful not to bruise or cut the fleshy bulbs.
- Clean and Dry: Shake off excess soil and let the rhizomes dry in a shady, frost-free spot for a couple of days.
- Store: Place the rhizomes in a box filled with slightly damp peat moss, sawdust, or perlite. Store them in a cool, dark place (like a basement or crawlspace) where temperatures stay between 40°F and 50°F.
Key Takeaway: You don't have to buy new bulbs every year. By lifting and storing them in the fall, you can enjoy the same giant cannas for many seasons to come.
Designing Your Garden with Giant Cannas
Because of their size, giant cannas offer unique opportunities for garden design. Here are a few ways we like to use them at Longfield Gardens to create a high-impact look.
The "Back of the Border" Hero
When planning a flower bed, the general rule is to put the shortest plants in the front and the tallest in the back. Giant cannas are the ultimate "back of the border" plants. They provide a solid, colorful wall that makes the colors of smaller perennials and annuals in front of them pop.
Living Privacy Screens
If you have a neighbor’s fence that isn't very attractive or a patio area that feels too exposed, giant cannas are a perfect solution. Planting a row of Canna Tall Australia creates a thick, leafy screen that provides privacy all summer long. Because they grow so fast, you get your privacy much sooner than you would by planting shrubs or trees.
Tropical Container Spills
You can grow giant cannas in containers, but you need to go big! A large, heavy pot (such as a whiskey barrel or a large ceramic planter) is necessary to keep the plant stable. Surround the base of the canna with "spiller" plants like sweet potato vine or trailing petunias. This creates a "thriller, filler, spiller" arrangement on a massive scale.
Realistic Expectations for Growth
While we call these "giant" cannas, it's important to remember that their final height is influenced by your local environment. A canna in a hot, humid climate like Georgia may reach 10 feet, while the same variety in a cooler, shorter-season climate like Maine might only reach 6 or 7 feet.
Both results are a success! Even at 6 feet, these plants are significantly taller than most other garden flowers. The key is to enjoy the process and the lush, tropical texture they bring to your outdoor space. If your plant doesn't reach the maximum height listed on the package in its first year, don't worry. As the rhizome matures and grows larger over several seasons, the plant often gains more vigor and height.
Conclusion
Giant canna bulbs are one of the most rewarding additions you can make to your summer garden. Their ability to transform a space with towering stems and massive, colorful leaves is unmatched by almost any other plant. By providing them with a sunny spot, plenty of water, and a bit of food, you can create a tropical retreat right in your own backyard.
At Longfield Gardens, we believe that gardening should be an enjoyable and accessible experience for everyone. Giant cannas fit this philosophy perfectly because they are resilient, fast-growing, and high-impact. Whether you are planting a single variety in a large pot or a whole row for privacy, these plants are sure to bring a smile to your face every time you look out the window.
- Wait for warm soil (60°F) before planting outdoors.
- Give them 6-8 hours of sun and consistent moisture.
- Fertilize regularly to support their rapid growth.
- In cold zones, lift the bulbs in the fall to save them for next year.
The beauty of giant cannas lies in their dramatic presence and effortless style. With just a few simple steps, you can turn your garden into a lush, towering sanctuary that lasts all summer long.
Ready to start your own tropical oasis? The next step is to choose a sunny spot in your garden and imagine the height and color that giant cannas will bring to your home this season.
FAQ
How fast do giant cannas grow?
Once the weather warms up and daytime temperatures are consistently in the 70s or 80s, giant cannas can grow incredibly fast. It is common for them to grow several inches in a single week during the peak of summer. Starting them in pots indoors 4-6 weeks before the last frost can give them an extra head start. For more timing detail, see When Do I Plant My Canna Bulbs?.
Do giant canna bulbs need to be dug up every year?
This depends on your USDA hardiness zone. If you live in Zone 8 or warmer, you can usually leave the bulbs in the ground with a layer of mulch for winter protection. In Zones 7 and colder, the bulbs will likely freeze and rot if left outside, so it is best to dig them up and store them in a frost-free area for the winter.
Can I grow giant cannas in the shade?
While cannas are tough and will survive in partial shade, they really need full sun (at least 6-8 hours) to reach their "giant" heights. In the shade, the stems will be thinner and more prone to leaning, and you will see significantly fewer flowers. For the best results, always choose the sunniest spot available.
Why are the leaves on my giant canna turning brown at the edges?
Brown edges on canna leaves are usually a sign of "leaf scorch," which happens when the plant cannot take up water as fast as it is losing it through the leaves. This is common during very hot, windy weather. To prevent this, ensure you are watering deeply and consider applying a layer of mulch to help the soil hold moisture longer.