Can Tomatoes Get Too Hot In A Greenhouse?

Picture this: you’ve carefully cultivated a flourishing tomato plant in your greenhouse, eagerly anticipating the juicy, vibrant fruits that will soon grace your table. But wait, can tomatoes get too hot in a greenhouse? As an aspiring tomato grower, it’s essential to understand the delicate balance of temperature that tomatoes require in order to thrive. In this article, we will unravel the mysteries surrounding the impact of excessive heat on tomatoes in a greenhouse, providing you with valuable insights to ensure the success of your tomato-growing endeavors.

Can Tomatoes Get Too Hot In A Greenhouse?

Factors that Affect Greenhouse Temperature

Sunlight Exposure

The amount of sunlight that reaches the greenhouse plays a crucial role in determining its temperature. Tomatoes thrive in warm and sunny conditions, but excessive sunlight exposure can lead to overheating. It is important to balance the amount of sunlight that enters the greenhouse by using shading techniques or adjusting the positioning of the greenhouse in relation to the sun.

Greenhouse Ventilation

Proper ventilation is vital for maintaining a stable and optimal temperature inside the greenhouse. Without adequate airflow, heat can accumulate and reach levels that are detrimental to tomato plants. Openings such as windows, vents, and doors should be strategically placed to facilitate the exchange of hot air with cooler air from outside, preventing overheating.


Insulation plays a crucial role in regulating the temperature inside the greenhouse. During colder months, it helps retain heat, while during hotter periods, it prevents excessive heat from entering the structure. Adding insulation materials such as bubble wrap or double-glazed panels can provide better control over the greenhouse temperature, ensuring that it remains within the optimal range for tomatoes.

Shading and Cooling Systems

The use of shading and cooling systems is another effective way to prevent excessive heat buildup in the greenhouse. Installing shade cloth above the tomato plants can help reduce the intensity of sunlight and provide much-needed protection against excessive heat. Additionally, incorporating evaporative cooling systems or misting fans can aid in lowering the temperature inside the greenhouse on exceptionally hot days.

Optimal Temperature Range for Tomatoes

Ideal Daytime Temperature

Tomatoes thrive in temperatures ranging from 70°F to 85°F (21°C to 29°C) during the daytime. This temperature range ensures optimal growth, photosynthesis, and fruit development. Temperatures above this range can lead to adverse effects such as reduced fruit set and quality, while temperatures below the range can slow down growth and cause stunted plants.

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Recommended Nighttime Temperature

During the nighttime, tomato plants prefer slightly cooler temperatures. The ideal range for nighttime temperatures is between 60°F and 70°F (15°C to 21°C). This drop in temperature allows the plants to rest and recover from the daytime heat while still providing enough warmth for their metabolic processes.

Effects of Deviating from Optimal Temperature

Deviation from the optimal temperature range can significantly impact the growth and development of tomatoes. When exposed to temperatures above 90°F (32°C), the pollen becomes non-viable, leading to poor fruit set and reduced yields. Similarly, exposure to temperatures below 50°F (10°C) can cause flower drop and increase the risk of diseases such as blossom end rot.

Tomato Stress Responses

Tomatoes are resilient plants and can withstand moderate temperature stress. However, prolonged exposure to extreme temperatures, whether hot or cold, can trigger stress responses. These stress responses may include reduced photosynthesis, delayed growth, increased susceptibility to pests and diseases, and weakened overall plant vigor. It is crucial to provide optimal temperature conditions to ensure healthy tomato plants and maximize yield.

Potential Risks of Excessive Heat in Greenhouse

Leaf Damage

When tomatoes experience excessive heat, the leaves can become damaged. The high temperatures cause the leaves to wilt, become discolored, and even scorch. The damage to the leaves can hinder photosynthesis and nutrient uptake, which negatively impacts plant growth and tomato production.

Blossom Drop

High temperatures in the greenhouse can lead to blossom drop in tomato plants. When the temperature surpasses the optimum range, the developing flowers may not be pollinated properly, resulting in their premature shedding. This can significantly reduce fruit set and ultimately lower overall tomato yields.

Fruit Set and Ripening Issues

Excessive heat can interfere with the pollination process, leading to poor fruit set. Additionally, high temperatures can affect the rate of fruit ripening. Tomatoes may ripen prematurely, resulting in poor flavor and texture. Conversely, prolonged exposure to high temperatures can delay ripening, leading to uneven fruit development and reduced market value.

Reduced Overall Tomato Yield

The combined effects of leaf damage, blossom drop, and fruit set issues due to excessive heat can significantly impact overall tomato yields. The stress caused by excessive heat hampers the plants’ ability to produce and develop healthy fruits. It is therefore important to implement measures to control greenhouse temperature and minimize the risks associated with excessive heat.

Methods to Control Greenhouse Temperature

Greenhouse Ventilation Techniques

Proper ventilation is key to controlling temperature inside the greenhouse. By strategically placing vents, windows, and doors, you can promote airflow and prevent excessive heat buildup. Consider using automatic ventilation systems or manually adjusting openings to allow cool air to enter and hot air to escape. This can help maintain a more stable temperature range for tomato plants.

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Shade Cloth Installation

Installing shade cloth is an effective strategy to reduce the intensity of sunlight and limit heat buildup in the greenhouse. It provides a physical barrier that filters sunlight, preventing direct exposure to the tomato plants. Different shade cloth densities are available, allowing you to customize the amount of shading needed based on your specific greenhouse conditions.

Using Evaporative Cooling

Evaporative cooling systems utilize the principle of evaporation to lower the temperature inside the greenhouse. By introducing moisture into the air, these systems create a cooling effect. Installing misting fans or evaporative pads can help reduce the temperature, providing a more favorable environment for tomato plants.

Using Heat-Reflecting Mulch

Heat-reflecting mulch can be applied around tomato plants to minimize the amount of heat absorbed by the soil. This type of mulch is designed to reflect a portion of the incoming sunlight, reducing soil temperature and thus, reducing heat stress on the plants. Heat-reflecting mulch can be particularly useful in regions with high temperatures and intense sunlight.

Can Tomatoes Get Too Hot In A Greenhouse?

Choosing the Right Tomato Varieties for Greenhouse Cultivation

Heat-Tolerant Tomato Varieties

Selecting tomato varieties that are known for their heat tolerance is crucial when growing tomatoes in a greenhouse. Look for varieties specifically bred to withstand high temperatures, as they will have better chances of thriving in the controlled environment of a greenhouse. Heat-tolerant varieties typically exhibit traits such as drought resistance, early fruiting, and better disease tolerance.

Compact and Determinate Varieties

When choosing tomato varieties for greenhouse cultivation, consider selecting compact and determinate varieties. Compact varieties have a more controlled growth habit, which makes them easier to manage in limited space. Determinate varieties tend to have an earlier harvest period, which is useful when you want to maximize yield within a specific timeframe.

Considerations for High-Temperature Climates

If you live in an area with a consistently high-temperature climate, it is essential to choose tomato varieties that are specifically bred for such conditions. Look for varieties that have been developed to thrive in heat-intensive environments. These varieties are more likely to have traits that allow them to tolerate and perform well under the conditions found in a high-temperature climate.

Tips for Managing Heat Stress in Tomatoes

Proper Watering and Irrigation

Maintaining adequate soil moisture is crucial for managing heat stress in tomatoes. Water plants deeply but avoid overwatering, as excessive water can lead to root rot. Consider drip irrigation systems to deliver consistent moisture to the root zone while minimizing water loss through evaporation.

Applying Organic Mulch

Applying organic mulch around tomato plants can help regulate soil temperature and retain moisture. Organic mulch, such as straw or compost, acts as a protective layer that insulates the soil, reducing temperature fluctuations. Mulch also helps conserve water by reducing evaporation from the soil surface.

Avoiding Overcrowding

Proper plant spacing is essential for preventing heat stress in tomatoes. Overcrowding can restrict airflow and increase humidity levels within the greenhouse, promoting the development of diseases. Maintain adequate spacing between plants to allow for good air circulation, which aids in dissipating excess heat and reducing the risk of heat stress.

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Using Shade Structures

In addition to shading techniques, installing shade structures within the greenhouse can provide additional protection against excessive heat. Suspended shade cloth or shade nets can create shaded areas within the greenhouse, reducing the overall temperature and creating a more comfortable environment for tomato plants.

Common Mistakes to Avoid

Inadequate Ventilation

Neglecting proper ventilation is a common mistake that can lead to a buildup of heat in the greenhouse. Without sufficient airflow, the temperature inside the greenhouse can quickly rise to detrimental levels. Regularly check and adjust ventilation openings to ensure proper air exchange and temperature control.

Insufficient Shading

Failing to provide adequate shading can result in excessive heat exposure. Depending on the intensity of sunlight in your region, it may be necessary to install shading systems such as shade cloth, shade nets, or blinds. Avoid underestimating the impact of direct sunlight on tomato plants and take the necessary steps to provide sufficient shade.

Neglecting to Monitor Temperature

Not monitoring the temperature inside the greenhouse regularly can lead to significant problems. Fluctuations in temperature can affect the health and productivity of tomato plants. Use a reliable thermometer or an automated temperature monitoring system to keep track of the greenhouse temperature and take appropriate action if needed.

Improper Watering Techniques

Overwatering or underwatering tomatoes can both be detrimental. Finding the balance between providing adequate water and avoiding waterlogged conditions is crucial. Monitor soil moisture regularly and adjust watering practices accordingly. Remember that consistent and appropriate watering is key to minimizing heat stress in tomato plants.

Understanding the Signs of Heat Stress in Tomatoes

Wilting Leaves

One of the primary signs of heat stress in tomatoes is wilting leaves. As the temperature rises, the moisture within the plant evaporates rapidly, causing the leaves to droop and wilt. Wilting leaves can be a result of excessive heat and can also indicate dehydration. It is important to identify the cause and take immediate action to alleviate heat stress.

Leaf Curling

Tomatoes suffering from heat stress often exhibit leaf curling. The edges of the leaves curl inward, a response to the heat as the plant tries to reduce the surface area exposed to the intense sunlight. Curling leaves can impair photosynthesis, affecting the plant’s ability to produce energy for growth and fruit development.

Blossom Drop and Fruit Deformities

High temperatures can lead to blossom drop and the development of deformed or misshapen fruits. When the temperature exceeds the optimal range, the flowers may not be pollinated properly, resulting in their premature fall. Additionally, heat stress can cause fruit deformities, such as misshapen or cracked tomatoes.

Sunscald and Browning

Sunscald is a common problem in tomatoes exposed to intense heat. It occurs when the fruits are exposed to direct sunlight without adequate protection, leading to sunburn and the development of pale or white spots on the skin. Browning of leaves and fruits can also occur as a result of heat stress, indicating cell damage and reduced plant health.


Maintaining the optimal temperature range in your greenhouse is crucial for successfully cultivating tomatoes. Factors such as sunlight exposure, greenhouse ventilation, insulation, and shading are key considerations in managing temperature. By implementing proper control techniques, selecting heat-tolerant tomato varieties, and following best practices for heat stress management, you can ensure healthy tomato plants and maximize your yield. Avoid common mistakes and monitor for signs of heat stress, making adjustments as necessary. With the right knowledge and attention to detail, you can create a favorable environment for your tomatoes to thrive, even in the heat of a greenhouse.