Coleus (Plectranthus scutellarioides) is a popular ornamental plant, cherished for its vibrant and diverse foliage. These plants are a common sight in gardens and as houseplants. Originating from warm, tropical regions, coleus thrives when temperature conditions are favorable. Understanding their specific temperature requirements is important for their health and survival.
Ideal Temperature Range for Coleus
Coleus plants flourish in warm environments, ideally between 68°F and 100°F (20°C to 38°C). For optimal growth and vivid foliage colors, a narrower range of 75°F to 90°F (25°C to 32°C) is preferred. These tropical plants are sensitive to cold; temperatures below 60°F (15.5°C) can cause stress or damage. When temperatures consistently drop below 50°F (10°C), coleus growth can be hindered, leading to stunted development and leaf loss.
A light frost is particularly detrimental, often causing rapid cellular death, with plants perishing within 12 to 24 hours. While coleus can tolerate temperatures as low as 41°F (5°C) in winter, sustained exposure to cooler conditions can reduce vigor and diminish leaf color. Freezing temperatures, specifically below 32°F (0°C), are lethal to coleus, as they are not frost-tolerant.
Identifying Cold Damage
When coleus plants are exposed to temperatures below their tolerance, they exhibit several visual signs of cold damage. Leaves may wilt or droop as cell damage occurs, losing their normal rigidity. This wilting indicates cold shock, especially if the plant has been adequately watered. Following initial wilting, leaves often show discoloration, appearing with white or yellow spots, or the entire leaf may change color.
More severe cold exposure can lead to leaves turning brown or black, eventually developing a mushy appearance. This blackening and mushiness indicate significant cellular damage, often meaning affected parts are unsalvageable. If the cold has been severe enough to impact the roots, the root ball may become loose in its pot, signifying extensive damage that severely compromises the plant’s survival. The plant’s overall health declines rapidly, often leading to its demise.
Protecting Your Coleus from Cold
Protecting coleus from cold temperatures is important for their survival, especially in regions prone to temperature dips. For outdoor plants, particularly those in containers, moving them indoors before temperatures fall below 60°F (15.5°C) is a proactive measure. If an unexpected cold snap is forecasted, temporary coverings like sheets or blankets can offer some protection to in-ground plants. In zones where freezing temperatures are common, bringing entire potted coleus plants indoors for overwintering is a practical approach.
When moving coleus indoors, select a location that provides bright, indirect light, such as a south- or southeast-facing window. It is also important to keep indoor coleus away from cold drafts and air conditioner vents. An alternative to bringing in entire plants is to take cuttings before cold weather arrives. These cuttings can be rooted in water or damp potting mix and grown indoors, providing new plants for the following season. Once rooted, these smaller plants can be placed in sunny windows and gradually reintroduced to outdoor conditions when warmer spring weather returns.