Growing Cannas in Water: A Simple Guide

Table of Contents

1. Introduction
2. Why Grow Cannas in Water?
3. Choosing the Right Cannas for Your Water Feature
4. Preparing to Move Cannas into Water
5. How to Pot Cannas for Aquatic Growth
6. Water Depth and Placement
7. Sun and Temperature Requirements
8. Fertilizing Cannas in Water
9. Maintenance and Grooming
10. Overwintering Cannas Grown in Water
11. Creative Ways to Use Cannas in Water
12. Troubleshooting Common Issues
13. Summary of the Aquatic Canna Process
14. FAQ

Introduction

Imagine transforming your backyard pond or a simple patio urn into a lush, tropical oasis with towering leaves and vibrant, exotic blooms. Many gardeners are surprised to learn that the bold, sun-loving canna lily is just as comfortable in a water feature as it is in a traditional flower bed. At Longfield Gardens, we enjoy helping you discover new ways to showcase these versatile plants, and growing them in water is one of the most rewarding methods for achieving a high-impact look.

Whether you have a dedicated garden pond or just a decorative water-filled container, cannas can provide the height and color you need. This guide is designed for any gardener who wants to explore aquatic planting with confidence. We will cover which varieties work best, how to pot them for water, and how to keep them thriving all season long.

With the right preparation and a bit of summer sun, you can easily enjoy the dramatic beauty of aquatic cannas.

Why Grow Cannas in Water?

Cannas are naturally semi-aquatic plants, meaning their wild ancestors often grew in boggy areas and along the edges of rivers. While we usually plant them in well-drained garden soil, they are incredibly adaptable to "wet feet." In fact, many varieties grow faster and larger when they have constant access to moisture.

One of the greatest benefits of growing cannas in water is the reduction in maintenance. During the hottest weeks of summer, cannas in traditional garden beds can require daily watering to prevent their large leaves from wilting. When grown in a pond or a water-filled pot, they have a steady supply of hydration. This makes them an excellent choice for busy gardeners or those living in hot, dry climates where keeping up with irrigation is a challenge.

Beyond the practical benefits, cannas add a unique architectural element to water features. Most pond plants, like water lilies, sit low on the surface. Cannas provide the necessary vertical interest, reaching heights of three to six feet. Their broad, paddle-shaped leaves—which come in shades of green, bronze, burgundy, and even variegated stripes—create a stunning backdrop for smaller aquatic plants.

Choosing the Right Cannas for Your Water Feature

While many standard canna varieties can adapt to life in the water, there is a specific group known as "water cannas" or Longwood hybrids. These were specifically bred to thrive in aquatic environments. They tend to be more vigorous in submerged conditions and often produce flowers that are held well above the foliage.

However, do not feel limited to only specialized aquatic hybrids. Many popular garden cannas also perform beautifully in water. Varieties with dark or colorful foliage, such as those often available through us, look particularly striking against the reflection of the water. When selecting a variety, consider the scale of your water feature. Smaller dwarf varieties are perfect for container water gardens, while the taller, giant varieties are better suited for the edges of larger ponds.

If you are just starting out, we suggest choosing a variety that is already known for its vigor. Plants with strong, thick rhizomes are usually the most successful when transitioning from soil to water, and a bold selection like Canna Tall Tropicanna is a good example of the kind of plant that makes a dramatic water-garden focal point.

Key Takeaway: While specialized "water cannas" exist, most vigorous garden cannas can adapt to aquatic life if they are transitioned correctly. Focus on the height and foliage color that best complements your space.

Preparing to Move Cannas into Water

The most important rule for growing cannas in water is that they should not be submerged while they are dormant. If you place a dry, dormant rhizome directly into a pond, it is likely to rot before it has a chance to sprout. Success begins with an active, growing plant.

We recommend starting your canna rhizomes in pots with standard potting soil first. Keep them in a warm, sunny spot and water them regularly until they have produced at least two or three sets of healthy leaves. This tells you the plant has established a root system and is ready to handle the transition to a wetter environment.

Once the plant is actively growing and the outdoor water temperature has reached at least 65°F (18°C), you can begin the process of moving it to its permanent summer home. If you want a broader overview of planting and care, the Learn with Longfield hub is a useful place to start.

Transitioning Your Plant

1. Start with a canna that is already 6 to 12 inches tall.
2. Ensure the outdoor air and water temperatures are consistently warm.
3. Check that the root system is well-developed by gently lifting the plant from its starter pot.
4. If the plant looks healthy and robust, it is ready for the pond.

How to Pot Cannas for Aquatic Growth

Potting a plant for a pond is slightly different than potting for a garden. You cannot use standard, peat-based potting soil in a water feature. Because peat is light and airy, it will float out of the pot and cloud your water, creating a messy environment for any fish or other plants.

Instead, use a heavy garden soil or a specialized aquatic planting medium. Heavy clay-based soil is ideal because it stays at the bottom of the pot and provides a stable anchor for the large canna roots. If your backyard soil is heavy clay, you are in luck—it is actually perfect for this task.

Step-by-Step Aquatic Potting

• Select a heavy pot: Choose a sturdy plastic pot with drainage holes. A 2-to-5-gallon size is usually sufficient for a single canna rhizome.
• Fill with heavy soil: Fill the pot about two-thirds full with heavy garden soil or aquatic media. Do not add vermiculite or perlite.
• Position the plant: Place the growing canna in the center. Ensure the top of the rhizome is just below the soil surface.
• Top with gravel: This is a crucial step. Add a 1-to-2-inch layer of washed pea gravel or small stones over the top of the soil. This prevents the soil from washing away and keeps the plant weighted down.
• Lower into the water: Slowly lower the pot into your water feature. The goal is to have the water level sitting about 1 to 4 inches above the soil surface.

Water Depth and Placement

Placement is everything when it comes to aquatic cannas. They are not deep-water plants like some lilies. Instead, they prefer "wet feet," where their roots are submerged but their crowns are relatively close to the surface.

In a pond setting, the best place for a canna is on a marginal shelf. These are the shallow ledges built into the sides of a pond. If your pond does not have shelves, you can create a makeshift one by stacking flat rocks or using inverted plastic crates to raise the pot to the correct height.

For decorative containers, you can simply place the potted canna inside a larger, waterproof urn or pot. Fill the larger container with water until it reaches the desired height above the canna's soil. This "pot-in-a-pot" method is a simple win for patio decorating, as it keeps the canna hydrated and looking fresh even in the peak of summer heat. For more practical growing help, see Gardening Essentials.

Key Takeaway: Cannas should be submerged so that only 1 to 4 inches of water covers the top of the pot. Placing them too deep can hinder their growth and limit oxygen to the roots.

Sun and Temperature Requirements

Cannas are children of the sun. To get the best foliage color and the most blooms, they need at least six to eight hours of direct sunlight every day. If they are placed in a shady corner of a pond, they may become "leggy" as they stretch for light, and they will produce far fewer flowers.

Temperature also plays a major role in their success. Cannas love heat and will not start growing vigorously until the weather is truly warm. In many regions, this means waiting until late May or June to move them into the water. If the water is too cold, the plant will sit idle. Once the summer heat kicks in, however, you will see them take off, often growing several inches in a single week.

Because water holds temperature differently than soil, your aquatic cannas might start a little slower in the spring but stay warmer longer into the autumn. This extended warmth can often lead to a spectacular late-season bloom. If you are unsure about timing for your area, the Hardiness Zone Map can help you match your planting schedule to your climate.

Fertilizing Cannas in Water

Cannas are heavy feeders. They need plenty of nutrients to support those massive leaves and bright flowers. When they are grown in soil, we usually recommend a balanced granular fertilizer. In a water environment, the approach is a bit different to protect the water quality.

The most effective way to feed aquatic cannas is by using aquatic fertilizer tablets. These are designed to be pushed deep into the soil of the pot. They release nutrients slowly and directly to the roots without leaching into the water and causing algae blooms.

During the peak growing season (from June through August), you can feed your cannas once a month. This ensures they have the energy to keep producing new flower spikes. If you notice the leaves starting to look pale or yellow, it is often a sign that the plant is hungry and needs an extra dose of nutrients.

Feeding Tips for Success

• Use only specialized aquatic fertilizer tabs.
• Push the tabs deep into the soil, at least 3 inches down.
• Follow the package instructions for the number of tabs based on your pot size.
• Avoid liquid fertilizers, as these can cloud the water and harm pond life.

Maintenance and Grooming

Maintaining cannas in water is very similar to maintaining them in the garden. The primary task is "deadheading," which involves removing spent flowers. When a flower cluster has finished blooming, cut the stem back to the next side bud or leaf. This encourages the plant to put its energy into new blooms rather than seed production.

As the season progresses, some of the lower leaves may turn brown or yellow. This is natural as the plant grows taller. Simply trim these off with a clean pair of garden shears to keep the plant looking tidy.

Cannas are vigorous growers, and in a water environment, they can quickly outgrow their pots. If you notice the pot looks like it is bulging or if the plant is becoming top-heavy and tipping over, it may be time to divide it or move it to a larger container. However, most gardeners find that one potting at the start of the season is enough to last until frost. The Shipping Information page is handy if you are planning an order around your local planting window.

Overwintering Cannas Grown in Water

Cannas are tropical plants and cannot survive freezing temperatures. When grown in water, they are even more vulnerable because the water can quickly turn into ice, which will destroy the rhizome.

As soon as the first frost blackens the foliage in the autumn, it is time to bring them in.

1. Remove the pot from the water: Let it drain for a day or two in a shady spot.
2. Cut back the foliage: Trim the stalks down to about 2 to 4 inches above the soil line.
3. Clean the rhizomes: Carefully remove the plant from the pot and wash away the heavy pond soil.
4. Dry and store: Let the rhizomes air dry for a few days. Store them in a cool, dry place (between 45°F and 55°F) in a box filled with peat moss, perlite, or vermiculite.

It is important to keep the rhizomes slightly moist but not wet during storage. Check on them once a month during the winter. If they look shriveled, give them a very light mist of water. If any look soft or molded, remove them immediately to keep the rest of the batch healthy.

Creative Ways to Use Cannas in Water

The versatility of growing cannas in water opens up many design possibilities. You don't need a huge landscape to enjoy this look.

• The Patio Water Urn: Place a single, tall canna in a large ceramic pot filled with water. Surround the base with floating plants like water lettuce for a finished look.
• The Bog Garden: If you have a low spot in your yard that stays soggy after rain, this is a perfect place for a canna. They will help soak up the excess moisture while adding beauty to a difficult area.
• The Pond Backdrop: Use cannas along the back edge of a pond to create a living "wall" of green. This adds a sense of privacy and makes the water feature feel like a secluded tropical getaway.
• Color Blocking: Pair cannas with contrasting foliage. For example, a bronze-leafed canna looks spectacular next to the bright lime-green of a taro plant (Elephant Ear), which also thrives in wet conditions.

By experimenting with different varieties and placements, you can find the perfect way to incorporate these aquatic beauties into your landscape. For more design inspiration, the Garden Basics Design page offers helpful ideas for combining color and form.

Key Takeaway: Cannas are highly versatile. From a simple patio urn to a large bog garden, they provide dramatic height and color wherever there is plenty of sun and water.

Troubleshooting Common Issues

While cannas are generally easy to grow in water, you might encounter a few minor hurdles. The most common issue is the pot tipping over. Because cannas grow tall and have large leaves, they act like sails in the wind. Ensure your pots are heavy and well-weighted with gravel. If a pot keeps tipping, you can wedge it between heavy rocks or use a wider, lower-profile container.

Another potential issue is "Canna Leaf Roller." These are small caterpillars that roll themselves up in the leaves. If you see leaves that are stuck shut or have holes in a straight line, this is likely the culprit. Simply unroll the leaf and remove the caterpillar by hand, or trim off the affected leaf.

Lastly, if your canna isn't blooming, it almost always comes down to a lack of sun or a lack of food. Ensure the plant is getting at least six hours of direct light and that you are keeping up with your monthly aquatic fertilizer tabs. For related growing tips and inspiration, the cannas blog category has more ideas from Longfield Gardens.

Summary of the Aquatic Canna Process

Growing cannas in water is a rewarding project that yields professional-looking results with very little effort. By following a few simple steps, you can ensure your plants stay healthy from the first sprout of spring to the final frost of autumn.

• Start with actively growing plants, not dormant rhizomes.
• Use heavy garden soil and top with gravel to keep the water clear.
• Submerge pots only 1 to 4 inches deep on a pond shelf or in a container.
• Provide maximum sunlight and regular aquatic fertilizer.
• Bring plants indoors before the water freezes in the winter.

At Longfield Gardens, we believe that gardening should be an enjoyable and creative adventure. Transitioning cannas to a water garden is a fantastic way to see these familiar favorites in a whole new light. With their bold leaves and bright flowers, they are sure to become the highlight of your summer garden.

If you are ready to add a tropical touch to your yard, consider trying a few cannas in your water features this year. The results are often even more impressive than those grown in the ground, and the ease of care makes them a true garden win. You can also explore our Assorted Cannas collection if you want a ready-made mix.

FAQ

Can any canna variety grow in water?

Most vigorous canna varieties can adapt to growing in water if they are already actively growing before being submerged. While "water cannas" are specifically bred for this, many standard garden varieties also thrive with "wet feet" as long as the water is shallow and the weather is warm. If you want a mix of forms and colors, Canna Assorted Collection is a convenient option.

How deep should I submerge the canna pot?

The ideal depth is to have the water level sitting between 1 and 4 inches above the top of the soil in the pot. You want the roots and the base of the stems to be underwater, but you should avoid submerging the entire plant. Placing them too deep can prevent the plant from getting enough oxygen.

Why are my canna leaves turning yellow in the water?

Yellowing leaves are usually a sign of a nutrient deficiency or a lack of sunlight. Cannas are heavy feeders and require monthly aquatic fertilizer tablets when grown in water. Ensure your plant is also receiving at least six to eight hours of direct sunlight daily to maintain its vibrant color. A colorful option such as Canna Tall Australia can also make a striking display.

Do I need to take cannas out of the water in the winter?

Yes, cannas are tropical plants and will not survive if the water freezes. Once the first frost hits, you should remove the pots from the water, cut back the foliage, and store the rhizomes in a cool, dry place indoors until the following spring. If you need more general planting guidance, the Learn center is a good reference.