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Greenhouse Overheating – 10 Tips How To Protect Your Crop

In the wake of a recent Intergovernmental Panel on Climate Change (IPCC) report highlighting the immediate repercussions of global warming on greenhouse agriculture, safeguarding your commercial greenhouse from extreme heat waves has become paramount. Over the past decade, greenhouse temperatures have risen by 1°C (1.8°F), with further escalation predicted. Greenhouse overheating pose three significant challenges:

  1. Reduced Yields: Crops’ yields may decline by up to 30% due to heat stress hindering photosynthesis and plant health.
  2. Pest and Disease Pressure: Higher temperatures make plants more susceptible to pests and diseases, resulting in increased losses and expenses.
  3. Energy Costs: Cooling demands amplify energy usage, straining growers with augmented costs.

What Happens If a Greenhouse Is Too Hot?

Greenhouse overheating pose a significant challenge to commercial greenhouse operators.

Ideally, you should have a way to monitor the temperature in greenhouse. Different crops have different optimal temperature ranges, but as a general rule, temperatures above 90F (32C) can cause stress for many common greenhouse crops. High temperatures often come with low humidity, which can further stress plants. If your humidity levels are consistently below 30%, that could be an additional sign that your greenhouse is too hot.

When temperatures rise significantly above a plant’s optimal growth range, they experience heat stress, disrupting their physiological processes. This can lead to wilted leaves, reduced fruit size, and in severe cases, plant death. You may also observe leaf curling, scorched leaf edges, or excessive ‘transpiration’—a plant’s cooling mechanism akin to human sweating. These signs indicate that your crops are struggling with the heat and need your timely intervention.

10 Ways To Protect Your Plants From Greenhouse Overheating:

1. Choose Heat-Tolerant Varieties of Crops

Not all crops are created equal when it comes to heat tolerance. Some crops, such as tomatoes, peppers, and cucumbers, can tolerate higher temperatures than others, such as lettuce and strawberries.

Best Heat-Tolerant Varieties of Crops for Greenhouses

Choosing heat-tolerant varieties of crops can be an effective strategy to protect your greenhouse from extreme heat waves. Here are some crops known for their heat tolerance:

  • Tomatoes: Varieties like ‘Solar Fire,’ ‘Heatmaster,’ and ‘Summer Set’ are known for their heat tolerance and would be suitable for a greenhouse enduring high temperatures.
  • Peppers: Both sweet and hot peppers generally love heat. Varieties such as Habanero, Jalapeno and Cayenne are particularly heat-tolerant.
  • Cucumbers: Varieties such as ‘Sweeter Yet’ and ‘Marketmore 76’ perform well in high heat.
  • Melons: Most melons are heat-loving fruits. Varieties like ‘Honey Dew Green,’ ‘Cantaloupe,’ and ‘Watermelon’ thrive in warmer conditions.
  • Okra: This vegetable is known for its heat and drought tolerance.
  • Eggplant: Varieties like ‘Black Beauty’ and ‘Ghostbuster’ can handle high temperatures.
  • Basil: This herb is known to be hardy and grows well in the heat.
  • Squash: Both summer and winter varieties tend to be heat-tolerant.

Hear-tolerant types of crops: cucumbers, tomatoes, peppers, eggplants, squashes

Remember, even heat-tolerant varieties need proper care and attention during heatwaves. Regular watering, shading during the hottest part of the day, and proper ventilation can protect from greenhouse overheating and help ensure plants survival and productivity.

2. Shade Cloth Can Protect Crops.

Professional greenhouse shade cloth is one of the ways to cool your greenhouse in the summer. It reduce the amount of sunlight that enters inside, which can help to keep your greenhouse cool. Shade cloth comes in a variety of  different colors and densities, so growers can choose the right type for their specific needs. If your greenhouse is located in a hot climate, you will need to choose a shade cloth with a darker color and a higher density.

3. Use Greenhouse Fans and Ventilation.

Fans and ventilation can help to circulate air in a greenhouse, which can help to remove hot air and replace it with cooler air. This is especially important during hot weather, when the air inside a greenhouse can quickly become stagnant and hot.

There are a few different ways to calculate the ventilation system for a greenhouse. One way is to use the following formula:

Ventilation rate = (Q * A) / (T2 - T1)


  • Ventilation rate is the amount of air that needs to be exchanged per minute.
  • Q is the heat load of the greenhouse.
  • A is the area of the greenhouse.
  • T2 is the desired temperature inside the greenhouse.
  • T1 is the ambient temperature outside the greenhouse.

6 types of greenhouse ventilation systems

4. Setup Evaporative Cooling Pads.

Evaporative cooling pads cool air by evaporating water. They are most effective in dry climates. To maintain their effectiveness, the pads should be kept clean and the water used should be pure. Evaporative cooling pads can increase humidity levels, so they should be used with ventilation or dehumidification systems.

5. Install Environmental Controllers.

Use environmental controllers to control and monitor heating in your greenhouses to ensure that your crops are getting the right amount of heat at the right times.

perfect solution to keep greenhouse cool in summer and protect from overheating

GrowDirector 3 PRO is a commercial-grade environmental control system that can be used to control a variety of conditions in greenhouses, including temperature, humidity, light levels, and CO2 levels. It can also be used to control heating, cooling, and ventilation systems. This user-friendly and modular system that is easy to set up and use has a web-based interface that can be accessed from anywhere with an internet connection. It also has a mobile app to control the system remotely. If you are a commercial grower, we encourage you to consider using GrowDirector 3 PRO to control and monitor heating in your growing facility and keep greenhouse cool in summer. Discover how to choose a perfect greenhouse automation.

6. Monitor the temperature and humidity in the greenhouse closely.

If the temperature or humidity gets too high you get the risk to the greenhouse overheating. Your greenhouse is a controlled environment and understanding the temperature and humidity levels is paramount for the health of your plants. Use advanced sensor technology, like GrowDirector’s Intelligent Climate Control System, to keep close tabs on these critical factors or automatic temperature sensor for greenhouse. Not only will this system indicate the current conditions, but it also allows you to set desired levels. When extremes in temperature or humidity are detected, the system will automatically adjust, protecting your plants from possible heat stress. Remember, a well-monitored greenhouse is a productive greenhouse.

7. Inspect the greenhouse regularly for signs of plants heat stress.

Regular inspection of your greenhouse can help you catch these symptoms early. Remember, early intervention is key to managing heat stress.

How do I know if my greenhouse is too hot?

The symptoms of plant heat stress in greenhouse crops

The symptoms of heat stress in greenhouse crops

8. Use a Drip Irrigation System.

This system applies water directly to the root zone, reducing water loss due to evaporation and runoff. It also prevents overwatering, which can promote fungal diseases especially in hot and humid conditions.

9. Implement Thermal Screen Systems.

These systems involve the use of retractable screens, which are designed to control both incoming light and heat, providing a dual function. During the day, thermal screens can reflect a portion of the sunlight to reduce heat buildup within the greenhouse. At night, these screens act as a thermal blanket, trapping heat and preventing rapid cooling. This effectively maintains a consistent, optimum temperature within the greenhouse, which is beneficial for plant health and productivity. Thermal screens can be manual or automated, with the latter providing ease of use and greater precision in climate control. By effectively managing temperature, thermal screens play a crucial role in protecting your crops from extreme temperature fluctuations and heat stress.

10. Apply a Cool Roof Coating.

This is a specially designed reflective paint-like substance that can be applied to the roof of your greenhouse. The coating reflects more sunlight than a standard roof, which means it absorbs less heat. As a result, the temperature inside your greenhouse can be significantly reduced. A cool roof coating not only helps in maintaining a conducive internal temperature but also reduces the reliance on additional cooling systems, leading to energy savings.

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