Viola cornuta ‘Costa’ is a popular garden plant, celebrated for its prolific, vibrant blooms. These cheerful flowers offer a delightful, long-lasting display of color, particularly in cooler conditions. Their compact size and abundant flowering make them a favored choice for consistent visual appeal.
Characteristics and Garden Uses
Viola cornuta ‘Costa’ grows 6 to 8 inches tall and spreads up to 12 inches, with a mounding or spreading habit. Its vivid blue-purple flowers are smaller than pansies but more numerous, creating a dense blanket of color. The plant’s crinkled, round, green leaves remain throughout the growing season. Its compact form and extended blooming period make it versatile for containers, hanging baskets, window boxes, border fronts, rock gardens, and as ground cover in mass plantings or along pathways.
Planting and Site Selection
The optimal time for planting Viola cornuta ‘Costa’ varies by climate. In cooler regions, spring planting is suitable, while in areas without winter frost, fall planting is often preferred. For direct sowing, prepare the planting area by amending and loosening the soil. If starting seeds indoors, sow 8 to 12 weeks before the last heavy frost.
When transplanting, choose a location with full sun to partial shade and well-draining soil. Violas prefer loamy, nutrient-rich soil with a slightly acidic to neutral pH. Incorporate organic matter like compost into the top 6-8 inches to improve drainage and fertility. Space mounding varieties 6 to 8 inches apart, and spreading types 10 to 12 inches apart, ensuring the plant crown is level with the soil surface. After planting, water thoroughly to settle the soil.
Viola ‘Costa’ Care Essentials
Light Requirements
Viola cornuta ‘Costa’ thrives in full sun (6-8 hours daily) or partial shade. While it tolerates shadier conditions, blooming may be less profuse. In hotter climates, afternoon shade helps mitigate heat stress and prolong the blooming period.
Soil Preferences
Viola ‘Costa’ prefers moist, well-drained soil rich in organic matter. Good drainage prevents waterlogging, which can harm the root system. Incorporating compost enhances soil structure and nutrient content, especially in sandy or heavy clay soils.
Watering Needs
Maintain consistent soil moisture for Viola ‘Costa’, avoiding overwatering. The soil should be evenly moist but not waterlogged. Check soil moisture by feeling the top inch or two; water if dry. Plants typically need about 1 inch of water per week from rain or irrigation during the growing season. Water deeply in the early morning or late afternoon, directing water to the soil to prevent fungal diseases. Yellowing or crispy leaves indicate underwatering, while soft, limp leaves suggest overwatering. Adjust watering frequency based on weather conditions, providing more water during hot, dry spells and less during cooler, wetter periods.
Fertilization
If soil is adequately prepared with organic matter, Viola ‘Costa’ may not need additional fertilization. To promote vigorous growth and blooming, or if soil lacks organic content, apply a general-purpose garden fertilizer. Use a slow-release fertilizer at planting or when seedlings are 2-4 inches tall, or a liquid fertilizer for flowering plants. Always follow product instructions, as excessive fertilization can cause issues like root rot. Container-grown plants may need more fertilizer due to nutrient depletion. Annual topdressing with compost also supports plant health.
Pruning and Deadheading
Deadhead Viola ‘Costa’ by removing entire spent flower stems back to a leaf node or the plant’s base. This encourages continuous blooming by preventing seed production and directing energy to new flowers. Light pruning helps maintain plant shape and promotes bushiness, especially if plants become leggy. Cutting back scraggly plants in midsummer, particularly after a bloom flush or during hot weather decline, can encourage new growth and a fall re-bloom, keeping the plant tidy and vibrant.
Addressing Common Problems
While Viola cornuta ‘Costa’ is generally robust, issues can arise. Pests like aphids and slugs may affect plants; dislodge aphids with water spray, and manually remove slugs or use baits. Powdery mildew, appearing as white spots on leaves, can occur in humid conditions; ensure good air circulation through proper plant spacing to prevent it. Root rot, often from overwatering or poor drainage, causes wilting, yellowing leaves, and a mushy base. Prevent it by maintaining consistent, non-excessive moisture and well-drained soil. During high heat, Viola ‘Costa’ may experience heat stress, leading to reduced blooming and vigor. Provide afternoon shade and sufficient water to help the plant survive and rebound when cooler temperatures return.