Calibrachoa, often called "Million Bells," is a tender perennial native to South America, particularly Brazil and Uruguay. In its natural habitat, it thrives in warm, temperate climates with mild winters. This plant is typically grown as an annual in colder regions because it is not frost-tolerant. Its survival during winter depends heavily on temperature, light, and care adjustments to mimic its native conditions.
Calibrachoa is sensitive to freezing temperatures. Exposure to frost or prolonged cold below 40°F (4°C) can damage or kill the plant. While some varieties may briefly tolerate light frost, most will not survive harsh winter conditions outdoors. This makes overwintering indoors or in protected environments essential for its survival in colder climates.
To overwinter Calibrachoa, bring potted plants indoors before the first frost. Place them in a bright, sunny location, such as a south-facing window, where they receive at least 6 hours of sunlight daily. Reduce watering slightly to prevent root rot, as the plant's growth slows in winter. Maintain indoor temperatures between 50–60°F (10–15°C) to keep the plant dormant but alive.
Before bringing Calibrachoa indoors, prune back leggy or dead growth to encourage compact, healthy regrowth in spring. Remove any pests, such as aphids or spider mites, to prevent infestations indoors. Lightly fertilize with a balanced, diluted fertilizer to support root health during dormancy, but avoid overfeeding.
For gardeners without indoor space, Calibrachoa can be propagated via cuttings before winter. Take 3–4 inch stem cuttings, remove lower leaves, and root them in water or moist potting mix. Once rooted, these cuttings can be grown indoors under grow lights. Alternatively, mulch outdoor plants heavily and cover them with frost cloth, though this method is less reliable for survival.
Overwintering Calibrachoa can be challenging due to its susceptibility to low light, pests, and fungal diseases indoors. Insufficient light may cause weak, spindly growth, while overwatering can lead to root rot. Regularly inspect the plant for pests and ensure proper air circulation to mitigate these risks.
As temperatures warm in spring, gradually acclimate Calibrachoa to outdoor conditions. Start by placing the plant in a shaded, sheltered spot for a few hours daily, increasing exposure over 1–2 weeks. Once nighttime temperatures consistently stay above 50°F (10°C), it can be permanently moved outdoors. Resume regular watering and fertilizing to encourage vigorous spring growth.
