How to Grow Cannas in Water for a Stunning Backyard Pond

Table of Contents

1. Introduction
2. Understanding the Versatility of Cannas
3. Choosing the Best Varieties for Your Water Feature
4. Preparing to Plant: The Importance of Timing and Temperature
5. The Best Methods for Growing Cannas in Water
6. Feeding and Fertilizing Aquatic Cannas
7. Managing Height and Stability
8. Winter Care and Overwintering
9. Common Questions About Water Cannas
10. Designing with Water Cannas
11. Conclusion
12. FAQ

Introduction

Imagine the striking silhouette of lush, tropical foliage rising directly from the surface of your garden pond. Cannas are famous for their bold leaves and vibrant, orchid-like flowers, but many gardeners are surprised to learn that these sun-loving plants are just as happy in the water as they are in a flower bed. At Longfield Gardens, we love how cannas bring vertical drama and a touch of the tropics to water features, creating a focal point that lasts from early summer right through the first frost.

Growing cannas in water is a rewarding project that is much simpler than it looks. Whether you have a large koi pond, a small pre-formed basin, or even a decorative container on your patio, these plants are remarkably adaptable. This guide will walk you through everything you need to know about selecting the right varieties, planting them securely in an aquatic environment, and keeping them thriving all season long. We designed this for anyone who wants to expand their water gardening skills and enjoy the effortless beauty of "wet feet" gardening.

By matching the right planting method to your specific water feature, you can enjoy a season of lush growth and brilliant blooms.

Understanding the Versatility of Cannas

Cannas are naturally found in tropical and subtropical regions where they often grow along the edges of rivers, marshes, and wetlands. This makes them "marginal" plants, meaning they thrive in the transition zone between dry land and open water. Because they have evolved to handle seasonal flooding, their rhizomes (the thick, underground stems) are incredibly efficient at pulling nutrients and oxygen from saturated environments.

There are two main categories of cannas you might consider for your water garden: true water cannas and terrestrial hybrids. True water cannas, such as the Canna glauca hybrids, were specifically bred to live in shallow water. These varieties, often referred to as Longwood hybrids, feature slightly different leaf shapes and are exceptionally vigorous in aquatic settings. However, many common garden cannas also adapt beautifully to life in a pond if they are transitioned correctly.

True Water Cannas vs. Land Cannas

The Longwood series, developed at the famous Longwood Botanical Gardens, includes popular varieties like ‘Tropicanna’, ‘Endeavour’ (red flowers), and ‘Ra’ (yellow flowers). These are the "gold standard" for pond enthusiasts because they are naturally resistant to the rot that can occasionally affect land-based varieties if the water is too deep or cold.

That said, many terrestrial cannas—the kind you typically plant in your garden borders—will also thrive in water. Varieties with dark or variegated foliage, such as those with bronze leaves or bright yellow stripes, add a spectacular layer of color to a pond. The key is to remember that while they love water, they still need plenty of sunshine and warmth to produce those iconic flowers.

Choosing the Best Varieties for Your Water Feature

When you are deciding which cannas to grow in your water feature, consider the scale of your space. Some cannas can reach heights of six to eight feet, which looks magnificent in a large pond but might overwhelm a small patio tub.

• Tall Varieties: These are perfect for the back of a pond or for creating a privacy screen. They provide a sense of enclosure and can act as a backdrop for shorter aquatic plants like water lilies.
• Dwarf Varieties: If you have a smaller water feature, look for dwarf or "mini" cannas. These typically stay under three feet tall, making them much easier to manage in pots and less likely to tip over in the wind.
• Foliage Focus: Don't just look at the flowers. Cannas with blue-green, burgundy, or striped leaves provide visual interest even when the plant isn't in bloom. For example, varieties with "tiger" stripes or multi-colored veins look incredible reflected in the water.

Key Takeaway: Most cannas are "marginal" plants that love having their roots in moist soil or shallow water. While specific water canna hybrids are available, many standard garden varieties can also be adapted to pond life with great success.

Preparing to Plant: The Importance of Timing and Temperature

One of the most important rules for success with cannas in water is waiting for the right temperature. Cannas are tropical plants at heart, and they do not like cold water. If you place a rhizome or a young plant into a chilly pond in early spring, it may sit dormant or struggle to establish itself.

We recommend waiting until your pond water consistently reaches at least 65°F (18°C). In most parts of the US, this happens a few weeks after the last frost date. If you want a head start, you can plant your canna rhizomes in pots with soil indoors or in a greenhouse about 4 to 6 weeks before you plan to move them outside. Once the plant has a few sets of leaves and the pond has warmed up, it will transition to the water much more quickly and vigorously. For more general planting timing, see how to plant a canna bulb.

Matching Light to Location

Cannas are sun-worshippers. To get the best foliage color and the most flowers, your water feature should receive at least 6 to 8 hours of direct sunlight per day. While they can grow in partial shade, they often become "leggy" (tall and thin) as they stretch toward the light, and their flowering will be significantly reduced.

The Best Methods for Growing Cannas in Water

There are several ways to incorporate cannas into your water garden. The method you choose depends on the type of water feature you have and how much maintenance you want to perform.

1. The Potted Pond Method

This is the most popular and reliable way to grow cannas in water. It involves planting the canna in a sturdy plastic pot and then submerging that pot into the pond.

• Select a Heavy Pot: Use a plastic nursery pot without large side holes. A 2-gallon or 5-gallon pot is usually sufficient. Since cannas can grow quite tall, a heavy pot helps prevent the plant from tipping over in the wind.
• Use the Right Soil: This is a crucial step. Do not use standard potting soil that contains perlite or vermiculite. These materials are designed to be light and airy, which means they will float right out of the pot and create a mess in your pond. Instead, use heavy garden soil or a specialized aquatic planting medium. Clay-heavy soil is actually excellent for this purpose because it stays put and holds onto nutrients.
• Planting Depth: Place the rhizome about 2 to 3 inches deep in the soil, with any growing tips pointing upward. Cover the soil with a 1-inch layer of pea gravel or small river stones. This "mulch" keeps the soil in the pot and prevents fish (like curious koi) from digging up the roots.
• Submerging: Slowly lower the pot into the water. The top of the pot should be submerged about 2 to 6 inches below the water surface.

2. The Bog Garden Method

If you have a boggy area near your pond or a shallow shelf that stays permanently saturated, you can plant cannas directly into the mud. Bog gardens provide a more natural look, as the plants appear to grow right out of the earth at the water's edge.

In a bog setting, you don't need to worry as much about pots tipping over. Simply dig a hole in the saturated soil, tuck the rhizome in, and firm the mud around it. As long as the area stays consistently wet, the cannas will thrive.

3. Bare Root in Bio-Filters or Gravel

Some pond owners grow cannas "bare root" in gravel-filled bio-filters or waterfalls. In this setup, the roots grow directly into the moving water, where they act as a natural filter by absorbing excess nitrates and phosphates. This helps keep the pond water clear and healthy for fish.

To do this, wash all the soil off the roots of an established canna plant and Nestle the roots into the gravel. Ensure the crown of the plant (where the stems meet the roots) is just at or slightly above the water level to prevent the main stem from softening.

What to Do Next:

• Wait for the pond water to reach 65°F before planting.
• Choose a heavy pot and fill it with clay-based garden soil (no perlite!).
• Top the soil with gravel to keep it from floating away.
• Position the pot so the top is 2–6 inches below the water surface.

Feeding and Fertilizing Aquatic Cannas

Cannas are "heavy feeders," meaning they require plenty of nutrients to produce their large leaves and bright flowers. When they are grown in garden soil, they get nutrients from the earth and supplemental fertilizer. In a pond, they can pull some nutrients from the water (which is great for water clarity), but they usually need a little extra help to reach their full potential.

Using Aquatic Fertilizer Tabs

The easiest and most effective way to feed cannas in water is by using aquatic fertilizer tablets. These are specially formulated to dissolve slowly and stay tucked into the soil around the roots, rather than leaching into the open water and fueling algae growth.

During the peak growing season (usually June through August), push one or two fertilizer tabs into the soil of each pot every 4 to 6 weeks. Always follow the instructions on the product packaging, as different brands have different concentrations.

Nutrient Absorption and Water Clarity

One of the hidden benefits of growing cannas in water is their ability to clean the pond. Because they grow so fast, they consume a lot of the nutrients that would otherwise feed string algae or turn the water green. By "competing" with the algae for food, your cannas help maintain a balanced and clear ecosystem.

Managing Height and Stability

One interesting quirk of growing cannas in water is that they often grow taller than their land-based counterparts. The constant access to moisture and nutrients allows them to reach impressive heights. While this is beautiful, it can lead to stability issues.

Preventing Tipping

A tall canna in a lightweight pot acts like a sail in the wind. If your pot tips over, it can spill soil into the pond or damage the plant's stems.

• Use Wide Pots: A wider base provides more stability than a tall, narrow one.
• Add Weight: You can place a few heavy bricks or large stones at the bottom of the pot before adding soil.
• Group Pots Together: Placing several pots close together can provide mutual support.
• Strategic Placement: Position your taller cannas in areas of the pond that are somewhat shielded from the strongest winds, such as near a fence or a wall of the house.

Trimming and Deadheading

To keep your water cannas looking their best, you should remove spent flowers. This process, called deadheading, encourages the plant to put its energy into producing new blooms rather than setting seeds. Once a flower spike has finished blooming, simply snip it off just above the next leaf or flower bud.

If a leaf becomes tattered or turns yellow, cut it off at the base of the stem. This keeps the plant looking tidy and prevents decaying organic matter from falling into the pond, which can affect water quality over time.

Winter Care and Overwintering

Cannas are perennial in USDA hardiness zones 8 to 11, where they can often stay in the water year-round (though they will go dormant in winter). However, in zones 7 and colder, the rhizomes will freeze and rot if left in the water through the winter.

Moving Cannas Indoors

For gardeners in colder climates, you have two main options for saving your cannas for next year:

1. The "Garage" Method: Before the first hard frost, lift the pots out of the pond. Cut the foliage back to about 3 or 4 inches above the soil line. Let the pots drain and move them into a cool, frost-free area like a basement or an attached garage. The soil should be kept barely moist—just enough so the rhizomes don't completely shrivel up.
2. Lifting and Storing Rhizomes: Remove the plant from the pot and wash away the soil. Cut off the foliage and let the rhizomes air-dry for a day or two in a shady spot. Store them in a box filled with slightly damp peat moss or vermiculite in a cool, dark place (around 45–55°F).

In the spring, once the danger of frost has passed and the pond is warming up again, you can repot the rhizomes and start the cycle over. Longfield Gardens provides a wide selection of cannas each spring if you want to add new colors or textures to your collection.

Common Questions About Water Cannas

Does Growing in Water Cause Rot?

A common concern for new water gardeners is whether the rhizomes will rot. While "land" plants often rot in standing water, cannas are uniquely adapted to it. Rot usually only occurs if the water is too cold or if the plant is submerged too deeply before it has started active growth. By waiting for warm water and keeping the pot at a shallow depth (2–6 inches), you can practically eliminate the risk of rot.

Can I Grow Cannas in a Container Without a Pond?

Absolutely! You don't need a full-scale pond to grow cannas in water. You can use a decorative "pot-within-a-pot" system. Choose a large, waterproof decorative container (one without drainage holes). Place your planted canna in its nursery pot inside the decorative container and fill the outer container with water until it reaches the desired level. This is a fantastic way to enjoy the look of an aquatic garden on a balcony, patio, or deck.

What Should I Do If My Canna Stops Blooming?

If your canna is healthy and leafy but not producing flowers, it is usually due to one of two things: light or food. First, ensure it is getting at least 6 hours of full sun. If it is in a shady spot, move the pot to a sunnier location. Second, check your fertilization schedule. Cannas in water need regular feeding with aquatic tabs to sustain their bloom cycle throughout the summer.

Designing with Water Cannas

When planning your water garden, think of cannas as the "thriller" in the classic "thriller, filler, spiller" design method. Their height and bold texture make them the perfect centerpiece.

• Pairing with Water Lilies: The vertical leaves of the canna provide a beautiful contrast to the flat, floating pads of water lilies.
• Softening Edges: Use cannas to hide the edges of a pre-formed pond liner or to soften the transition between a stone patio and the water.
• Color Themes: Create a monochromatic look by pairing red-flowered cannas with red aquatic hibiscus, or go for a high-contrast tropical look by mixing orange cannas with purple-flowering pickerel weed.

Conclusion

Growing cannas in water is one of the easiest ways to bring a lush, tropical feel to your home landscape. These versatile plants are more than just pretty faces; they are hard-working members of a pond ecosystem, helping to filter the water and provide structure to your garden. By choosing the right varieties, using heavy soil, and providing plenty of sun and food, you can enjoy a spectacular display of foliage and flowers all season long.

At Longfield Gardens, we believe that gardening should be an enjoyable and rewarding journey. Whether you are a seasoned pond owner or a beginner looking to try something new with a patio water feature, cannas are a fantastic choice that rarely disappoints. If you want to learn more about our 100% Quality Guarantee, we’re happy to help.

Final Tips for Success:

• Start Warm: Only move cannas into the water once it reaches 65°F.
• Secure the Soil: Use clay-based garden soil and a gravel topper.
• Feed Regularly: Use aquatic fertilizer tabs every 4–6 weeks during the summer.
• Enjoy the View: Place your water cannas where you can see them from your favorite seating area!

Ready to start your aquatic garden? The next step is to choose your favorite colors and get your pots ready for the warm weather ahead. For a quick refresher on seasonal timing, check the Shipping Information page before you order.

FAQ

Can any canna grow in water?

While almost all cannas enjoy "wet feet" and can tolerate saturated soil, some terrestrial varieties are more sensitive than others. True water canna hybrids (like the Longwood series) are the most reliable, but many popular garden varieties like ‘Pretoria’ or ‘Tropicanna’ also thrive in shallow water if transitioned during warm weather.

How deep should I submerge the pot?

For most cannas, the ideal depth is 2 to 6 inches of water over the top of the pot. If the water is too deep (more than 10–12 inches), the plant may struggle to get enough oxygen or may become unstable. Keeping the crown of the plant near the water's surface is the safest approach for healthy growth.

What soil should I use for aquatic cannas?

Avoid standard potting mixes with perlite or vermiculite, as these will float away. Instead, use heavy garden soil, unscented kitty litter (the plain clay kind), or specialized aquatic soil. Clay-heavy soils are excellent because they anchor the plant and prevent nutrients from leaching too quickly into the pond water.

Do cannas in water need special fertilizer?

Yes, because the water can wash away standard granular fertilizers, it is best to use aquatic fertilizer tablets. These are designed to be pushed into the soil near the roots, where they provide a slow release of nutrients without encouraging excessive algae growth in the surrounding pond water.