Canna plants are striking additions to any garden, known for their bold foliage and vibrant flowers. These tropical and subtropical plants are a popular choice for gardeners. With their upright growth and diverse color palettes, Cannas can transform garden beds, borders, and containers. They provide continuous color throughout the warmer months.
Understanding Canna Plants
Canna plants vary widely in appearance. Varieties range from compact dwarf types, 2-3 feet tall, to towering specimens over 6 feet. Their foliage comes in shades of deep green, bronze, burgundy, and variegated patterns. These large, paddle-like leaves add an architectural element to the landscape.
Canna flowers bloom in a spectrum of colors including reds, oranges, yellows, pinks, and bicolors. These blossoms emerge on tall stalks, resembling gladioli or irises, from early summer until the first frost. Cannas grow from rhizomes, which are fleshy, underground stems that store nutrients, allowing the plant to spread and return year after year in suitable climates. They thrive in warm, humid conditions.
Planting Canna Rhizomes and Plants
Planting Cannas correctly is key, whether starting with dormant rhizomes or potted plants. Plant after all danger of frost has passed in spring, when soil temperatures reach 60°F (15°C) or higher. Cannas need full sun, at least six to eight hours daily, for good growth and flowering. Well-draining soil is important, as waterlogged conditions can lead to rhizome rot. Amend heavy clay soils with organic matter like compost or aged manure to improve drainage and fertility.
When planting rhizomes, position them horizontally about 4-6 inches deep with any visible “eyes” facing upwards. Space rhizomes 1 to 2 feet apart. For potted Canna plants, dig a hole twice as wide as the root ball and just as deep, ensuring the top of the root ball is level with the surrounding soil. After planting, thoroughly water the area to settle the soil around the roots and remove air pockets. Consistent moisture helps establish plants quickly.
Ongoing Canna Plant Care
Once established, Cannas need consistent care for healthy growth and blooming throughout the season. They are thirsty plants, especially during hot, dry periods, requiring regular watering to keep the soil moist but not waterlogged. Deep watering once or twice a week is more effective than frequent shallow watering, encouraging deeper root development. Monitor soil moisture regularly to determine watering needs, as conditions vary with climate and container size.
For continuous flowering, Cannas benefit from regular fertilization. Apply a balanced granular fertilizer, such as a 5-10-5 or 10-10-10 formulation, every 4-6 weeks during the growing season. A liquid feed every two to three weeks also provides nutrients. Removing spent flowers (deadheading) encourages more blooms by preventing seed production. Regularly inspect plants and remove any yellowing or damaged leaves to maintain health and appearance.
Winterizing and Storing Canna Rhizomes
In regions with freezing winters, Canna rhizomes are not hardy and must be dug up and stored indoors. This process begins after the first light frost in autumn, which signals dormancy and causes foliage to blacken. Cut back Canna stalks to about 4-6 inches above ground. Gently loosen the soil around the rhizome clump with a garden fork, then lift the clump, taking care not to damage the rhizomes. Shake off excess soil.
After digging, allow rhizomes to air dry in a cool, shaded area for several days to cure, which helps prevent rot during storage. Once dried, gently brush off any remaining soil but do not wash them. Store rhizomes in a cool, dark, frost-free location between 40-50°F (4-10°C), such as a basement or unheated closet. Place them in cardboard boxes, paper bags, or mesh sacks, loosely covered with a slightly moist medium like peat moss, vermiculite, or sawdust to maintain humidity and prevent desiccation. Check rhizomes periodically throughout winter for signs of rot or dryness to ensure viability for replanting.
Troubleshooting Common Canna Problems
Gardeners may encounter issues with Canna plants, though many problems can be resolved. A common concern is a lack of blooms, which can be attributed to insufficient sunlight; Cannas require full sun exposure to produce flowers. Yellowing leaves might indicate overwatering, leading to root rot, or a nutrient deficiency, particularly nitrogen. Ensuring well-draining soil and applying a balanced fertilizer can address these concerns.
Leaf spots, caused by fungal diseases, can appear as circular lesions on foliage, especially in humid conditions. Improve air circulation around plants and avoid overhead watering to prevent fungal development. Common pests include canna leaf rollers, which cause leaves to curl and become disfigured as larvae feed inside. Apply an organic insecticide or manually remove affected leaves to manage these pests. Spider mites and slugs also pose a threat; a strong spray of water can dislodge mites, while slug baits or barriers protect foliage from feeding damage.