The question of whether to cover plants when the temperature drops to \(50^{\circ}\text{F}\) (\(10^{\circ}\text{C}\)) can generally be answered with a no, but with important exceptions. For most common, established garden plants, \(50^{\circ}\text{F}\) is a transitional temperature that does not trigger immediate danger or damage. This temperature is significantly above the \(32^{\circ}\text{F}\) (\(0^{\circ}\text{C}\)) point where freezing occurs, meaning that a true frost or freeze event is not imminent. The need for protection at this level depends entirely on the specific plant species and the surrounding environmental conditions.
Understanding Cold Tolerance Levels
Plants experience two primary forms of cold-related damage: chilling injury and freezing injury, and these occur at different temperature ranges. Freezing injury happens when temperatures fall to \(32^{\circ}\text{F}\) or lower, causing ice crystals to form inside or between plant cells, which physically ruptures the tissue. This damage is often irreversible, resulting in blackened, mushy foliage that quickly collapses.
Chilling injury, however, affects plants at temperatures well above freezing, typically between \(32^{\circ}\text{F}\) and \(50^{\circ}\text{F}\) (\(0^{\circ}\text{C}\) and \(10^{\circ}\text{C}\)). This physiological disorder primarily impacts tropical and subtropical species that lack the cellular mechanisms to cope with extended cold exposure. The damage is not caused by ice but by changes in cell membrane structure, leading to metabolic imbalances that manifest as surface pitting, discoloration, and water-soaked areas.
Since \(50^{\circ}\text{F}\) falls at the upper boundary of the chilling injury range, most temperate plants are completely safe. However, species originating from very warm climates, such as basil, tomatoes, and certain ornamental tropicals, are highly sensitive. These warm-season crops may exhibit signs of stress or cease development if exposed to temperatures in the \(50^{\circ}\text{F}\) to \(55^{\circ}\text{F}\) range for an extended period.
Specific Variables Requiring Protection at 50 Degrees
While \(50^{\circ}\text{F}\) is not a danger zone for hardy plants, certain plant types and microclimate factors do necessitate protection. Tropical plants and heat-loving vegetables, including tomatoes, peppers, eggplant, and basil, are cold-sensitive and can suffer chilling injury at this temperature range. Even if the damage is not immediate, prolonged exposure can lead to stunted growth and reduced productivity.
Young seedlings and recently transplanted plants also have a much lower tolerance for cold due to their undeveloped root systems and tender new growth. These plants are more susceptible to shock and stress than established, mature specimens of the same species. New transplants should be given extra consideration, especially if the \(50^{\circ}\text{F}\) temperature is accompanied by other adverse conditions.
Microclimate elements can effectively lower the temperature experienced by the plant, even if the general air temperature remains at \(50^{\circ}\text{F}\). Wind chill can increase the rate of heat loss from the plant tissue, which is particularly damaging in combination with cold air. Furthermore, if the dew point is close to the air temperature, the resulting high humidity and moisture on the leaves can increase the risk of cold damage.
The duration of the cold period is another factor, as a brief dip to \(50^{\circ}\text{F}\) is less harmful than several consecutive nights at that level. A sheltered location, such as a garden bed next to a warm house wall, will also retain more heat than an open, exposed area. Assessing these site-specific variables is more important than the ambient temperature reading alone when deciding whether to cover plants.
How to Properly Cover Plants
When it is determined that plants require protection, the method of covering is crucial for effectively mitigating cold stress. The goal of covering is to trap the radiant heat rising from the soil and prevent it from escaping into the night air. Materials like old bed sheets, blankets, or commercial row covers are highly effective because they are breathable fabric that allows moisture to escape.
It is important to ensure the covering extends all the way to the ground and is secured with bricks or stones to create an insulated dome over the plant. This seal traps the warmer air and prevents cold air from seeping underneath the protective layer. Plastic sheeting can be used as a second layer over a fabric cover for added insulation and moisture protection, but plastic should never touch the foliage directly, as this can transfer cold and cause contact burn.
Using stakes or hoops to suspend the cover above the plant prevents the material from crushing the foliage and keeps it from directly conducting cold to the leaves. The cover should be put in place before sunset to capture the last of the day’s warmth. It is equally important to remove the covering promptly the next morning after temperatures have risen to prevent the plants from overheating and sustaining heat damage.
Specific Variables Requiring Protection at 50 Degrees
While \(50^{\circ}\text{F}\) is not a danger zone for hardy plants, certain plant types and microclimate factors do necessitate protection. Tropical plants and heat-loving vegetables, including tomatoes, peppers, eggplant, and basil, are cold-sensitive and can suffer chilling injury at this temperature range. Even if the damage is not immediate, prolonged exposure can lead to stunted growth and reduced productivity.
Young seedlings and recently transplanted plants also have a much lower tolerance for cold due to their undeveloped root systems and tender new growth. These plants are more susceptible to shock and stress than established, mature specimens of the same species. New transplants should be given extra consideration, especially if the \(50^{\circ}\text{F}\) temperature is accompanied by other adverse conditions.
Microclimate elements can effectively lower the temperature experienced by the plant, even if the general air temperature remains at \(50^{\circ}\text{F}\). Wind chill can increase the rate of heat loss from the plant tissue, which is particularly damaging in combination with cold air. Furthermore, if the dew point is close to the air temperature, the resulting high humidity and moisture on the leaves can increase the risk of cold damage.
The duration of the cold period is another factor, as a brief dip to \(50^{\circ}\text{F}\) is less harmful than several consecutive nights at that level. A sheltered location, such as a garden bed next to a warm house wall, will also retain more heat than an open, exposed area. Assessing these site-specific variables is more important than the ambient temperature reading alone when deciding whether to cover plants.
How to Properly Cover Plants
When it is determined that plants require protection, the method of covering is crucial for effectively mitigating cold stress. The goal of covering is to trap the radiant heat rising from the soil and prevent it from escaping into the night air. Materials like old bed sheets, blankets, or commercial row covers are highly effective because they are breathable fabric that allows moisture to escape.
It is important to ensure the covering extends all the way to the ground and is secured with bricks or stones to create an insulated dome over the plant. This seal traps the warmer air and prevents cold air from seeping underneath the protective layer. Plastic sheeting can be used as a second layer over a fabric cover for added insulation and moisture protection, but plastic should never touch the foliage directly, as this can transfer cold and cause contact burn.
Using stakes or hoops to suspend the cover above the plant prevents the material from crushing the foliage and keeps it from directly conducting cold to the leaves. The cover should be put in place before sunset to capture the last of the day’s warmth. It is equally important to remove the covering promptly the next morning after temperatures have risen to prevent the plants from overheating and sustaining heat damage.