Table of Contents
- Introduction
- What Are Canna Bulbs?
- Where Cannas Grow as Perennials
- Choosing the Right Spot
- How to Plant Canna Rhizomes
- Caring for Your Cannas Through the Summer
- How to Overwinter Perennial Canna Bulbs
- Growing Cannas in Containers
- Dividing Your Cannas for More Plants
- Troubleshooting Common Growth Questions
- Conclusion
- FAQ
Introduction
Few plants bring the vibrant energy of the tropics to a backyard quite like cannas. With their oversized, banana-like leaves and brilliant blooms in shades of red, orange, and yellow, they transform any space into a lush summer retreat. Whether you use them to create a privacy screen or as a bold focal point in a patio container, these plants are remarkably reliable and easy to enjoy.
At Longfield Gardens, we want every gardener to feel confident growing these stunning plants. While often called "bulbs," cannas actually grow from thick, underground stems known as rhizomes. In warm climates, they are true perennials that return year after year. In cooler regions, you can easily save them from one season to the next with a simple storage process.
This guide will show you how to plant, care for, and overwinter your cannas. We will cover the best spots for planting and how to ensure your plants thrive all summer long. By following these steps, you can enjoy the beauty of these perennial favorites for many years to come.
What Are Canna Bulbs?
While most people search for perennial canna bulbs, it is helpful to know that they are technically rhizomes. A rhizome is a fleshy underground stem that grows horizontally just beneath the soil surface. These structures store energy and nutrients for the plant, allowing it to push out vigorous new growth each spring.
The "perennial" nature of a canna depends largely on where you live. In the southern United States, cannas stay in the ground all year and sprout again as soon as the soil warms up. In northern zones, they are considered "tender perennials." This means they will not survive a freezing winter in the ground, but the rhizomes themselves stay alive if kept in a cool, dry place indoors.
Because they store so much energy, cannas are incredibly fast growers. A small rhizome planted in May can easily reach several feet in height by mid-summer. This makes them one of the most rewarding plants for gardeners who want high-impact results in a single season.
Where Cannas Grow as Perennials
Understanding your USDA hardiness zone is the first step to knowing how to treat your cannas. These plants are native to tropical and subtropical regions, so they crave warmth.
- Zones 8 through 10: In these warm climates, cannas are hardy perennials. You can leave them in the garden year-round. They may go dormant in the winter, but the roots remain healthy underground.
- Zone 7: This is a transition zone. In many years, cannas will survive the winter if you apply a thick layer of mulch—about six inches of straw or shredded leaves—to protect the soil from deep frost.
- Zones 3 through 6: In these cooler regions, cannas are treated as tender perennials. To keep them from year to year, you will need to lift the rhizomes in the fall and store them indoors.
Even if you live in a cold climate, the process of saving them is very straightforward. It allows you to keep your favorite varieties and watch your collection grow over time.
Choosing the Right Spot
Success with cannas starts with matching the plant to the right location. They are not demanding plants, but they do have two non-negotiable requirements: plenty of sun and consistent moisture.
Sunlight Needs
Cannas are sun-worshippers. To produce their best foliage color and the most blooms, they need at least six to eight hours of direct sunlight every day. If they are planted in too much shade, the stalks may become "leggy" as they stretch toward the light, and they may produce fewer flowers. If you are growing varieties with dark bronze or variegated leaves, full sun helps those colors stay vivid and saturated.
Soil and Drainage
In their native habitats, cannas often grow near the edges of ponds or in damp ditches. This means they love water. While many garden plants suffer from "wet feet," cannas are quite happy in moist soil. However, they still prefer soil that is rich in organic matter. Adding a bit of compost to your planting hole provides the nutrients they need to fuel their rapid growth.
Key Takeaway: For the biggest blooms and brightest leaves, pick the sunniest spot in your garden and ensure the soil stays consistently moist throughout the growing season.
How to Plant Canna Rhizomes
The best time to plant cannas is in late spring, once the threat of frost has passed and the soil has warmed to at least 60°F. Since they are tropical plants, they will sit idle in cold, damp soil. Waiting for the right temperature ensures they start growing immediately.
Planting Depth and Spacing
- Prepare the soil: Dig a hole about 4 inches deep.
- Position the rhizome: Lay the rhizome horizontally in the hole. Look for the "eyes" or growth points—these look like small bumps or pointed tips. Point these upward or to the side.
- Cover with soil: Fill the hole so the rhizome is covered by 2 to 3 inches of soil.
- Space them out: Cannas can become quite large. Space dwarf varieties about 1 to 2 feet apart. For tall varieties that can reach 5 or 6 feet, give them 2 to 3 feet of space so they don't crowd each other.
Initial Watering
After planting, water the area well to settle the soil around the rhizomes. You won't see growth above the ground for a few weeks, but plenty of activity is happening underneath as the roots establish themselves. Once you see the first green sprouts, you can begin a more regular watering schedule.
Caring for Your Cannas Through the Summer
Cannas are relatively low-maintenance once they get going. Because they grow so fast and produce such large leaves, they are "heavy feeders." This means they appreciate a little extra help to keep their energy up.
Water and Fertilizer
Keep the soil moist, especially during the hottest parts of July and August. If the edges of the leaves begin to turn brown and crispy, it is usually a sign that the plant needs more water.
For the best results, use a balanced, water-soluble fertilizer every few weeks during the peak growing season. This supports both the lush leaf production and the continuous flowering. Always follow the instructions on the product label for the best results.
Grooming and Deadheading
Canna flowers grow on stalks that rise above the foliage. As individual flowers fade, you can pinch them off to keep the plant looking tidy. Once an entire flower spike has finished blooming, cut that specific stalk down to where it meets the next set of leaves. This encourages the plant to put its energy into new flower spikes rather than producing seeds.
Next Steps for Summer Care:
- Check soil moisture twice a week during heat waves.
- Remove faded flowers to encourage new blooms.
- Apply a balanced fertilizer once a month.
- Watch for the first signs of new growth spikes emerging from the base.
How to Overwinter Perennial Canna Bulbs
If you live in a region with freezing winters, you can easily save your cannas for next year. The goal is to keep the rhizomes dormant and protected from freezing temperatures.
When to Dig
Wait until the first light frost kills the foliage. You will notice the leaves turning black or brown and drooping. This is a good thing—it signals to the plant that it is time to go dormant. After this happens, cut the stalks down to about 4 inches above the ground.
Digging and Cleaning
Carefully use a garden fork or shovel to lift the entire clump out of the ground. Dig a few inches away from the base to avoid slicing through the fleshy rhizomes. Gently shake off the excess soil. You can rinse them lightly with a hose if they are very muddy, but do not scrub them. It is important to keep the outer skin intact to prevent rot.
The Curing Process
Curing is a simple but vital step. Place your cleaned rhizomes in a dry, frost-free area like a garage or a shed for several days. This allows the outer skin to toughen up and any remaining moisture on the surface to evaporate. Curing helps prevent mold and rot during the long winter months.
Storing for Winter
Once the rhizomes are dry to the touch, it is time to pack them away.
- Storage Medium: Place the rhizomes in a cardboard box or a plastic bin with the lid left slightly cracked for airflow.
- Packing Material: Surround the rhizomes with slightly damp peat moss, vermiculite, or even shredded newspaper. This keeps them from drying out completely without making them wet enough to rot.
- Location: Store the box in a cool, dark, and dry place. An unheated basement, a crawl space, or a cool closet is ideal. The temperature should stay between 40°F and 50°F.
Check on your stored cannas once or twice during the winter. If the rhizomes look shriveled, mist the packing material with a little water. If you see any soft spots or signs of rot, remove those pieces immediately to keep the rest of the batch healthy.
Growing Cannas in Containers
If you have limited garden space or want to decorate a patio, cannas are excellent container plants. Growing them in pots also makes the overwintering process even easier.
Choose a large pot with plenty of drainage holes. A 12-inch pot is usually sufficient for one dwarf canna, while larger varieties may need a 15- to 18-inch container. Use a high-quality potting mix that retains moisture well.
The biggest challenge with container-grown cannas is keeping them hydrated. Pots dry out much faster than the ground, so you may need to water your potted cannas every day during the summer.
When winter arrives, you don't even have to dig the rhizomes up. Simply cut the foliage back, move the entire pot into a frost-free area, and stop watering. The soil in the pot acts as a protective blanket for the rhizomes until spring.
Dividing Your Cannas for More Plants
One of the most exciting things about cannas is how much they multiply. A single rhizome planted in the spring will often turn into a large clump by the fall. Dividing these clumps is an easy way to get more plants for free.
The best time to divide cannas is in the spring, just before you are ready to plant them back out.
- Look at the clump and identify the different sections.
- Use a clean, sharp knife to cut the rhizomes into smaller pieces.
- Ensure each piece has at least one "eye" or growth point (preferably two or three).
- Let the cut ends dry for a day before planting to allow them to "callous" over, which protects them from soil-borne diseases.
Sharing these extra divisions with friends and neighbors is a great way to spread the joy of gardening.
Troubleshooting Common Growth Questions
Cannas are generally very robust, but you might occasionally have questions about their performance. Here are the most common scenarios and how to handle them.
Slow to sprout: If your cannas haven't appeared by early June, check the soil temperature. Cannas often wait until the ground is truly warm before they wake up. You can give them a head start by planting them in pots indoors about 4 to 6 weeks before the last frost.
Lots of leaves but no flowers: This is usually caused by one of two things: not enough sun or not enough food. If your cannas are in a shady spot, consider moving them to a sunnier location next year. If they are in the sun, try increasing your fertilizer applications.
Holes in the leaves: Sometimes, caterpillars or "canna leaf rollers" may visit your plants. If you see rolled-up leaves or chew marks, you can usually remove the affected leaves or pick the pests off by hand. Keeping the plants healthy and vigorous is the best way to help them withstand minor insect visits.
Conclusion
Cannas are a fantastic choice for any gardener looking to add a touch of the tropics to their landscape. These resilient perennials reward a little bit of care with an explosion of color and texture that lasts until the first frost. Whether you live in a warm climate where they stay in the ground year-round or a cooler area where you store them for the winter, the results are always worth the effort.
By choosing a sunny spot, providing plenty of water, and following the simple storage steps in the fall, you can enjoy these beautiful plants for a lifetime. We at Longfield Gardens are proud to provide high-quality rhizomes to help you get your garden started.
Final Tips for Success:
- Always wait for warm soil before planting outdoors.
- Use containers for an easy way to bring tropical color to decks and patios.
- Keep your stored rhizomes cool and slightly dry to ensure they are ready for spring.
The next step is to choose your favorite colors and start planning your summer oasis. With their bold presence and easy-going nature, cannas are sure to become a highlight of your garden.
FAQ
Can I leave my canna bulbs in the ground during winter?
Whether you can leave them in the ground depends on your USDA hardiness zone. If you live in zones 8 through 10, they can stay outside year-round with no issues. In zone 7, they may survive with a thick layer of protective mulch, but in zones 6 and colder, the rhizomes must be dug up and stored indoors to survive the freezing temperatures.
When is the best time to dig up cannas for the winter?
The ideal time to dig them up is shortly after the first light frost has blackened the foliage. This frost tells the plant to go dormant and move its energy down into the rhizome. It is important to lift them before the ground freezes solid, as the rhizomes themselves cannot survive being frozen.
Do cannas need full sun to bloom?
Yes, cannas perform best when they receive at least six to eight hours of direct sunlight every day. While they can grow in partial shade, they will produce fewer flowers and the foliage may not be as vibrant. If you are growing them specifically for their blooms, a sunny location is essential.
Why are my cannas not flowering?
The most common reasons for a lack of flowers are insufficient sunlight or a lack of nutrients. Ensure your plants are in a spot that gets plenty of sun and try applying a balanced fertilizer every few weeks. Additionally, make sure you are not planting them too deep; the rhizomes should only be covered by 2 to 3 inches of soil.