Canna lilies are tropical plants prized for their large, banana-like foliage and vibrant flowers. These plants bring an immediate sense of the tropics to any garden space, thriving in warm, sunny conditions. Variegated cultivars are highly sought after for their multi-toned leaves, featuring patterns like stripes, mottling, or distinct borders in contrasting colors. This unique foliage offers season-long visual interest, even before the plant blooms. Growing these specialized varieties requires attention to their needs to ensure the colors remain crisp and prominent.
Understanding Variegation and Cultivars
The striking patterns on variegated canna leaves result from a genetic mutation causing certain leaf sections to lack chlorophyll. These areas cannot photosynthesize, appearing white, cream, or yellow, while the remaining tissue retains its green pigment. Because the plant has less total surface area for energy production, these varieties require more precise care.
Several popular cultivars showcase this characteristic, each with a distinct look. The ‘Pretoria,’ also known as ‘Bengal Tiger,’ is famous for its bright yellow and green striped foliage. ‘Stuttgart’ features large, angular patches of white and green, while ‘Tropicanna’ (‘Phasion’) displays red, yellow, and orange stripes. Recognizing the specific pattern helps in tailoring the plant’s care, particularly concerning sun exposure.
Essential Growing Conditions
Establishing a strong base for variegated cannas begins with proper planting and soil preparation. Cannas grow from thick underground stems called rhizomes, which should be planted after the last expected frost when the soil temperature warms to at least 65°F (18°C). The rhizome is typically placed two to four inches deep with the growing buds facing upward.
Cannas are heavy feeders and perform best in rich, organically amended soil that drains well but remains consistently moist. Amending the planting area with compost or aged manure improves soil structure and provides initial nutrients for vigorous growth. Since the large, soft leaves are prone to tearing, choose a planting site sheltered from strong winds.
Cannas thrive in full sun, receiving six to eight hours of direct light daily to promote the best flowering. Consistent moisture is necessary; insufficient water can cause leaves to crack or tear, especially in hot, dry weather. Deep watering once or twice a week is often necessary during peak summer to keep the soil evenly moist.
Specialized Care for Maintaining Leaf Color
Maintaining the vibrancy of variegated foliage requires a delicate balance of light and nutrition, as the white or yellow portions are more sensitive than the green parts. Too much intense, direct sun can easily scorch the non-pigmented areas of the leaves, causing them to turn brown and dry out. Gardeners in extremely hot climates may find that providing some afternoon shade helps preserve the crisp appearance of the variegation, especially on white-striped varieties like ‘Stuttgart’.
Conversely, plants that receive too little sunlight may suffer from a phenomenon called reversion, where the leaves begin to turn solid green in an attempt to maximize their limited energy production. Consistent, bright light is necessary to encourage the plant to maintain the expression of its variegation.
Fertilization must be managed carefully, as cannas are known to be heavy feeders throughout the growing season. High-nitrogen fertilizers should be avoided because nitrogen encourages green, leafy growth and accelerates reversion. Instead, use a balanced, slow-release fertilizer applied at planting, supplemented with a liquid feed every four to six weeks.
Regular maintenance includes removing any shoots that emerge with solid green leaves (reverted stems). These stems are often more vigorous than the variegated portions and must be promptly cut back to the rhizome to prevent them from outcompeting the patterned foliage. Also, monitor for pests like Canna leaf rollers and spider mites, which can damage the large leaves.
Seasonal Dormancy and Storage
In temperate climates where winter temperatures drop below freezing, canna lilies must be prepared for seasonal dormancy to protect the tropical rhizomes. This process begins in the fall, ideally after the first light frost causes the foliage to die back and yellow. This timing signals dormancy and allows the plant to store maximum energy in the rhizomes for the following year.
Once the foliage is frosted, cut the stems back to about six inches above the soil line before the ground freezes. Carefully lift the rhizome clumps from the soil, avoiding damage to their fleshy structure. After lifting, the rhizomes need a short curing period, air-drying in a cool, well-ventilated area for a few days to allow the outer skin to slightly toughen.
Proper winter storage requires a dark, dry, and frost-free environment where the temperature remains consistently cool, ideally between 40°F and 50°F (4°C to 10°C). Store the rhizomes in a breathable medium like slightly moistened peat moss or vermiculite, placed in a container that allows air circulation. Periodically check the stored rhizomes throughout the winter for signs of mold or excessive drying to ensure viability for spring replanting.