Canna ‘Blueberry Sparkler’ is a favorite for gardeners, bringing a tropical feel to landscapes with its bold statement. It features unique dark, almost black, foliage with subtle blue-grey undersides, providing a dramatic backdrop for its eye-catching blooms. The flowers are a striking red-orange, adorned with delicate yellow speckles that create a dazzling, “sparkling” effect. This canna cultivar typically grows to a mature height of approximately 6 feet, with a spread of around 4 feet, forming a sturdy, upright clump, adding vertical interest to garden designs.
Planting and Growing Your Canna ‘Blueberry Sparkler’
Successful cultivation of Canna ‘Blueberry Sparkler’ requires selecting the right location. These plants thrive in full sun, needing at least six hours of direct sunlight daily for robust growth and abundant flowering. Light shade may result in fewer blooms and weaker stems.
Canna ‘Blueberry Sparkler’ performs best in rich, well-drained soil with a slightly acidic to neutral pH (6.0-7.0). Incorporate 2 to 4 inches of compost or other organic matter before planting to enrich soil and improve drainage. Place rhizomes 1 to 2 inches below the soil surface with growth nodes pointing upwards, spaced 18 to 24 inches apart. Plant after the last spring frost when soil temperatures have warmed.
Maintain consistent soil moisture, keeping it evenly moist but not waterlogged. During hot summer weeks, a thorough soaking once a week, or even every other day, is beneficial. A thin layer of mulch helps retain moisture and regulate temperature.
Cannas are heavy feeders and benefit from regular fertilization to support vigorous growth and continuous blooming. Apply a balanced fertilizer (e.g., 5-10-5 or 10-10-10 NPK) monthly throughout the growing season. For a 5-10-5 ratio, apply 2 pounds per 100 square feet; for 10-10-10, use 1 pound per 100 square feet. Always water thoroughly after fertilizing.
Deadheading, the removal of spent blooms, encourages the plant to produce more flowers rather than expending energy on seed production. Once a flower spike has finished blooming, prune it down to the nearest side shoot, where a new flower spike can emerge. This helps maintain the plant’s aesthetic appeal and promotes a longer flowering season.
Overwintering Canna ‘Blueberry Sparkler’
In regions where winter temperatures consistently fall below USDA Hardiness Zone 7, Canna ‘Blueberry Sparkler’ rhizomes must be lifted and stored indoors to protect them from freezing temperatures. Overwintering is typically done in the fall, after the foliage has been killed back by the first light frost, but before the ground freezes solid. This timing allows the plant to store as much energy as possible in its rhizomes for the following growing season.
Steps for Overwintering
Cut back dead or frost-damaged foliage to 2 to 6 inches above ground.
Carefully dig and lift the entire rhizome clump, shaking off excess soil and rinsing clean.
Cure rhizomes by air-drying in a warm, dry, well-ventilated area (70-80°F) for about one week. This toughens the outer skin and reduces rot during storage. Remove any remaining foliage once cured.
Store dried rhizomes in a cool, dark, well-ventilated location (40-59°F / 4.5-15°C). Basements, cool cellars, or unheated closets are suitable.
Place rhizomes in peat moss, vermiculite, or sawdust within a cardboard box or paper bag to maintain humidity and prevent excessive drying. Periodically check for shriveling, disease, or pests, discarding affected ones.
Common Challenges and Solutions
Gardeners may encounter certain challenges when cultivating Canna ‘Blueberry Sparkler’.
Pests
Canna Leaf Rollers: Caterpillars roll up leaves to feed, creating holes and ragged edges. Inspect plants regularly, manually remove and destroy rolled leaves. For significant infestations, apply biological insecticides containing Bacillus thuringiensis (Bt) directly into rolled leaves, which specifically targets caterpillars without harming other beneficial insects.
Aphids and Spider Mites: These pests affect cannas, particularly in dry or stressed conditions. Aphids cluster on new growth, while spider mites cause stippling and fine webbing. Horticultural oils or insecticidal soaps can effectively control these soft-bodied pests when applied thoroughly to all affected plant surfaces. Consistent monitoring helps in early detection and management.
Diseases
Canna Rust: Caused by Puccinia thaliae, symptoms include small, orange-brown pustules on leaf undersides and tan spots on upper surfaces. Severe infections lead to leaf yellowing and premature drop. Promptly remove and dispose of infected leaves; do not compost. Ensure good air circulation and avoid overhead watering to prevent fungal development. In persistent cases, copper-based fungicides may be used according to product instructions.
Environmental Issues
Lack of Blooms: Often indicates insufficient sunlight or inadequate nutrient supply.
Yellowing Leaves: Can signal overwatering (leading to root issues) or a nutrient deficiency, particularly nitrogen.
Stunted Growth: May result from poor soil conditions, insufficient water, or nutrient imbalances.
Addressing these cultural conditions by adjusting light exposure, improving drainage, or providing appropriate fertilization can resolve many common growth challenges.