Introduction
Imagine the striking silhouette of a tropical canna lily, its vibrant petals and broad, banana-like leaves reflecting off the surface of a garden pond. For many gardeners, the sight of these lush beauties rising directly from the water is a highlight of the summer season. At Longfield Gardens, we love how canna lilies bring an immediate sense of the tropics to any landscape, whether they are tucked into a flower bed or gracing a water feature.
While we typically think of bulbs and rhizomes as needing well-drained soil, cannas are unique in their ability to adapt to very wet conditions. This article will explore whether you can grow these stunning plants in water without traditional garden soil and how to help them thrive in aquatic environments. Whether you are a beginner or a seasoned gardener, you can enjoy the dramatic impact of cannas in your water garden.
The short answer is yes, certain canna lilies can grow in water without soil, provided they have the right physical support and plenty of nutrients.
The Versatile Nature of Canna Lilies
Canna lilies are not true lilies, but rather members of the Cannaceae family, closely related to gingers and bananas. They grow from thick, fleshy underground stems called rhizomes. In their native habitats across the tropical and subtropical Americas, they often grow in damp ditches and along the marshy edges of rivers. This natural history makes them much more tolerant of "wet feet" than most other summer-blooming bulbs.
When we talk about growing cannas in water, we are essentially looking at their potential as "marginal plants." These are plants that grow with their roots submerged but their foliage and flowers held high above the water line. Because they are so adaptable, many home gardeners have transitioned them from the back of the border to the edge of the pond with great success.
It is important to remember that while cannas are tough, they are also heavy feeders. Their success in water depends on their ability to access minerals and energy, as well as the warmth of the summer sun. When you understand these basic needs, moving them into a water-based environment becomes a fun and rewarding garden project.
Aquatic Cannas vs. Terrestrial Cannas
Not all cannas are created equal when it comes to their love for water. While most garden cannas (Canna x generalis) can tolerate very damp soil, there is a specific group known as aquatic cannas or Canna glauca hybrids. These varieties have been specifically bred or selected for their ability to thrive with their roots completely submerged in water.
Canna glauca is a species native to the wetlands of South America. These plants often have narrower, more glaucous (blue-green) leaves and a more refined growth habit. Hybrids of this species are often the best choice for a pond or water feature because they are less prone to rot when submerged for long periods.
However, many of the standard varieties we offer at Longfield Gardens can also adapt to life in a water garden. Large-flowered "dinnerplate" styles and dwarf varieties can often transition to a pond environment if they are acclimated properly. The key is to start with a healthy, actively growing plant rather than dropping a dormant rhizome directly into deep water.
Can Canna Lilies Grow Without Soil?
The question of growing "without soil" usually brings to mind two different methods: growing in pure water (hydroponics) or growing in a soil-less medium like gravel or expanded clay.
Growing in Pure Water
If you place a canna rhizome in a vase of plain water, it will likely sprout and grow for a short time. However, this is rarely a long-term solution. Because cannas are "big eaters," they eventually run out of the nutrients stored within the rhizome. Without a way to anchor the roots or provide consistent fertilization, the plant will eventually weaken and fail to bloom. Additionally, an unsupported plant in pure water is top-heavy and will likely tip over as it grows to its full height.
Growing in Soil-less Media
This is the most successful way to grow cannas in water without traditional garden soil. In a pond or a decorative water container, you can "plant" the rhizome in a basket or pot filled with pea gravel, lava rock, or specialized aquatic planting media. This setup provides several benefits:
- Physical Stability: The weight of the gravel holds the rhizome in place and prevents the tall stalks from blowing over in the wind.
- Root Aeration: Water can circulate freely through the stones, bringing oxygen to the roots.
- Filtration: The roots of the canna act as a natural filter, absorbing excess nitrates and phosphates from the pond water, which helps keep the water clear.
Key Takeaway: While cannas can technically grow without soil, they still need a substrate like gravel to anchor their roots and a consistent source of nutrients to produce their signature blooms.
How to Plant Cannas for a Water Feature
If you want to move your cannas into a water feature, timing and technique are the quiet winners for success. It is always best to wait until the weather and the water have warmed up significantly before moving plants outdoors.
Start with Active Growth
One of the most common mistakes is placing a dormant, dry rhizome directly into a pond. This often leads to rot because the plant isn't "awake" enough to process the water. Instead, start your rhizomes in pots with a little bit of potting soil or compost indoors in the spring. Once the plant has developed a few strong leaves and a healthy root system, it is ready to be transitioned to the water. Starting canna bulbs indoors can give them the active growth needed for a smoother transition.
Choosing the Right Container
For water growing, use a plastic "pond pot" or a mesh aquatic basket. These containers have holes or a lattice-like structure that allows water to flow through the root zone. If you are using a standard plastic pot, you can drill several large holes in the sides and bottom.
The Planting Process
- Prepare the Rhizome: Gently wash away any soil from the roots of your pre-started canna.
- Positioning: Place the rhizome in the basket so that the "eyes" or the base of the stems are near the top.
- Fill with Medium: Fill the space around the roots with clean pea gravel or aquatic stones. Ensure the plant is steady and upright.
- Add Fertilizer: Since gravel contains no nutrients, you must add aquatic fertilizer tablets. Push these deep into the gravel near the root zone.
- Submerge Slowly: Lower the pot into your water feature. The water level should ideally be only 1 to 6 inches above the top of the gravel. Cannas like "wet feet," but they do not want to be "drowned" in deep water.
Setting the Scene: Sun and Temperature
Cannas are true sun-seekers. This requirement does not change just because they are growing in water. For the best floral display and the most vibrant leaf colors, your water feature should be in a spot that receives at least 6 to 8 hours of direct sunlight daily. For more guidance, see Longfield Gardens’ guide to canna lily lighting requirements.
The temperature of the water is also a major factor. Cannas are tropical plants that thrive when temperatures are between 70°F and 90°F. If your pond water is very cold (as it might be in early spring or if it is fed by a cold spring), the canna's growth will slow down significantly. In most US gardens, the ideal time to place cannas in a pond is late May or June, once the water has naturally warmed up.
Nutrients: Feeding Your Aquatic Cannas
If you were growing cannas in a garden bed, they would draw nutrients from the organic matter in the soil. In a water-and-gravel setup, you become the primary source of food. Cannas are known as "heavy feeders," meaning they require a lot of nitrogen and potassium to fuel their rapid growth and continuous blooming.
If your cannas are in a pond with fish, they will benefit from the natural waste the fish produce. However, this is usually not enough to support the massive growth of a 6-foot tall canna. We recommend using slow-release aquatic fertilizer tablets once a month throughout the growing season. These tablets are designed to sink and dissolve slowly, feeding the plant without causing a massive algae bloom in the surrounding water.
What to Do Next:
- Check your water temperature; ensure it is at least 60°F before submerged planting.
- Purchase aquatic-safe fertilizer tablets.
- Select a sunny spot in your pond or a large, decorative water bowl.
- Keep an eye on the water level to ensure the root zone stays submerged but the foliage stays dry.
Managing the "Mess": Algae and Water Quality
A common concern when growing plants in water without soil is the potential for algae. Algae thrives on the same things cannas do: sunlight and nutrients. When you add fertilizer to a water feature, there is a chance some of it will leach into the water and "feed" the algae.
To keep your water clear, focus on these simple steps:
- Don't over-fertilize: Use only the recommended amount of aquatic tablets.
- Use gravel as a barrier: A thick layer of gravel on top of the root zone helps keep the nutrients contained near the plant.
- Encourage competition: Cannas are actually great at fighting algae because they grow so fast. They out-compete the algae for the available nutrients in the water.
- Monitor water flow: In a small container or "patio pond," you may need to occasionally refresh the water to prevent it from becoming stagnant.
Canna Varieties for Water Growing
While we carry a wide range of beautiful varieties at Longfield Gardens, some are particularly well-suited for the transition to water. When choosing a variety for your pond or water bowl, consider the scale of your space.
- Tall Varieties: These can reach 5 to 6 feet in height and are perfect for the center of a large pond or as a "living screen" at the water's edge. Look for varieties with deep bronze or variegated foliage to add extra visual interest. Explore the Tall Cannas collection for larger-growing options.
- Dwarf Varieties: If you are growing in a smaller patio water bowl, dwarf cannas are the perfect fit. They usually top out at 2 to 3 feet, making them much easier to manage in a container.
- Foliage Focus: Some cannas are grown more for their leaves than their flowers. Varieties with striped or multi-colored leaves look stunning when paired with the reflective surface of the water.
Seasonal Care and Maintenance
Even in a water-based environment, cannas require a little bit of "housekeeping" to stay looking their best. Because they grow so quickly, they can eventually become crowded in their pots. Longfield Gardens’ canna care guide offers additional advice on seasonal maintenance.
Deadheading for More Blooms
Cannas produce multiple flower spikes on a single stem. Once a flower has faded, you can snip it off to encourage the next bud to open. When the entire flower spike has finished blooming, cut that specific stalk back to the next side shoot. This simple task keeps the plant focused on making new flowers rather than producing seeds.
Dividing Your Plants
Water-grown cannas can be incredibly vigorous. In a single season, a small rhizome can grow to fill an entire 5-gallon bucket. If you notice the pot becoming distorted or the plant's growth slowing down, it may be time to divide it. This is usually done in the spring before the new growth starts. Simply lift the clump, cut the rhizome into sections (making sure each section has at least one "eye"), and replant.
Overwintering Your Water-Grown Cannas
In most of the United States, cannas are considered tender perennials. This means they cannot survive a freeze. If you live in Zone 7 or colder, you will need to bring your cannas indoors. Check your canna growing zone to determine the best winter strategy.
The process for water-grown cannas is slightly different than for those in the ground:
- Lift Before the Hard Freeze: Once the first light frost has blackened the leaves, it is time to act.
- Drain and Trim: Remove the pot from the water and let it drain for a day. Cut the stems down to about 4 to 6 inches.
- Clean the Rhizomes: Remove the plant from the gravel and wash away any debris.
- Dry and Store: Let the rhizomes air dry in a cool, shaded spot for a few days. Then, store them in a box filled with slightly damp peat moss or perlite. Keep them in a frost-free area (like a basement or garage) where temperatures stay between 40°F and 50°F.
If you live in a very warm climate (Zone 9 or 10), you may be able to leave your cannas in the water year-round, provided the water does not freeze. However, even in warm areas, a yearly "cleanup" and division are recommended to maintain the plant's health.
Why Choose Water Growing?
You might wonder why someone would choose to grow cannas in water instead of the ground. Beyond the sheer beauty of the setup, there are several practical advantages:
- No Weeding: When you grow in a pond or a water bowl with gravel, weeds are rarely an issue.
- Automatic Watering: You never have to worry about the soil drying out. As long as the water level is maintained, your cannas are hydrated.
- Pest Resistance: Some common garden pests, like slugs and snails, find it much harder to reach plants that are surrounded by water.
- Versatility: This method allows people with limited garden space or poor soil to enjoy large, dramatic plants on a balcony, patio, or deck.
Simple Troubleshooting
If your water-grown cannas aren't blooming or look a bit pale, don't worry. Most issues can be solved by adjusting one variable at a time.
First, check the light. If the plant is in the shade for most of the day, it will produce plenty of green leaves but very few flowers. Move the container to a sunnier spot and wait two weeks to see if new buds appear.
Second, consider the food. Pale yellow leaves often indicate a lack of nutrients. If you haven't added fertilizer tablets recently, now is the time. Cannas use a lot of energy to build those massive leaves, and they will tell you quickly if they are "hungry."
Finally, check the water depth. If the rhizome is buried too deep in the water (more than 6-8 inches), it may struggle to breathe. Raising the pot slightly so the "crown" of the plant is closer to the surface often results in a quick burst of new growth.
Creating a Patio Water Garden
You don't need a massive backyard pond to grow cannas in water. A large, glazed ceramic pot or a galvanized metal trough can become a beautiful patio water garden.
Choose a container that is at least 15 to 18 inches deep and has no drainage holes. Place your potted canna (in its gravel-filled basket) inside the larger container. Fill the large container with water until it reaches the desired level. To make it a complete ecosystem, you can add floating plants like water lettuce or even a few small goldfish. This setup creates a stunning focal point that requires very little maintenance once established. For more container inspiration, see this guide to growing cannas in pots.
Key Takeaway: A "patio pond" with canna lilies is an easy win for gardeners who want high-impact tropical style in a small or manageable space.
Bringing it All Together
Growing canna lilies in water without soil is a fantastic way to experiment with the versatility of these tropical stars. By providing them with a sturdy anchor of gravel, a sunny location, and plenty of aquatic nutrients, you can enjoy a lush, flowering display all summer long.
At Longfield Gardens, we believe that gardening should be a rewarding and enjoyable experience. Whether you're planting your first rhizome in a decorative bowl or adding a dramatic backdrop to your garden pond, cannas are a reliable choice for success. Their ability to adapt to water environments makes them a unique and exciting addition to any home landscape. With just a little bit of preparation and the right variety, you’ll be well on your way to a stunning aquatic display.
Conclusion
Canna lilies are remarkably resilient and adaptable, making them the perfect candidates for water-based gardening. While they can grow without traditional soil, providing a substrate like gravel and a consistent supply of nutrients ensures they remain healthy and vibrant. Remember to prioritize sun, warmth, and heavy feeding to get the most out of your plants.
- Start with healthy, sprouted rhizomes rather than dormant ones for aquatic success.
- Use gravel or lava rock to provide physical support and stability in the water.
- Apply aquatic fertilizer tablets monthly to satisfy their large appetite.
- Overwinter the rhizomes indoors if you live in a cold climate to protect your investment.
"The beauty of canna lilies in a water feature is that they offer a high-reward, low-maintenance way to bring a tropical vibe to your outdoor space."
We are here to help you find the perfect varieties to start your own water-growing adventure. For more tips on caring for your summer favorites, explore the rest of our gardening guides.
FAQ
Can I grow any variety of canna lily in water?
While most canna lilies are adaptable and can handle "wet feet," the Canna glauca hybrids are specifically bred for aquatic environments. Standard garden varieties can also grow in water, but it is best to start them in a small amount of soil or transition them slowly to ensure the rhizome does not rot.
Do I need to use a pump or filter for a canna water container?
In a small patio water bowl, a pump is not strictly necessary, although it can help prevent mosquitoes and keep the water clear. In a larger pond, the canna lilies actually act as a natural filter themselves, helping to remove excess nutrients from the water.
How deep should I submerge my canna lily pot?
Ideally, the water level should be between 1 and 6 inches above the top of the planting medium (gravel). If the water is too deep, the plant may struggle to grow or the stems may become weak. "Marginal" placement is always the best approach for cannas.
What should I do if my water-grown canna isn't blooming?
The most common reasons for a lack of blooms are insufficient sunlight or a lack of nutrients. Ensure your plant receives at least 6 to 8 hours of direct sun and that you are using aquatic fertilizer tablets regularly, as gravel provides no natural nutrition.
