What Temperature Should A Greenhouse Be In The Winter?

During the winter months, maintaining the optimal temperature inside a greenhouse is crucial for the thriving of your plants. With the cold weather outside, finding the balance between warmth and cooling is key to ensure proper growth and prevent any damage to your beloved greenery. In this article, we will explore the ideal temperature range for a greenhouse in the winter, providing you with valuable insights on how to create the perfect environment for your plants to flourish. So, grab a hot beverage, cozy up, and let’s embark on this journey to discover the ideal winter temperature for your greenhouse!

Choosing the Right Temperature for a Winter Greenhouse

Factors to Consider

When it comes to choosing the right temperature for a winter greenhouse, there are several important factors you need to consider. These factors will help you create the optimal environment for your plants to thrive in the colder months.

The Role of Plant Types

Different plant types have different temperature requirements, so it’s important to understand the specific needs of the plants you plan to grow in your winter greenhouse.

Cool-season crops such as lettuce, spinach, and kale are tolerant of cooler temperatures and can even withstand light frost. On the other hand, warm-season crops like tomatoes and peppers prefer higher temperatures and may struggle in a winter greenhouse.

Tropical and exotic plants have specific temperature requirements and may require additional heating methods to survive the colder winter months. Perennial flowers and shrubs, while more resilient to cold temperatures, still need to be monitored and provided with adequate heat.

Temperature Range for Winter Greenhouses

In a winter greenhouse, it’s crucial to maintain a temperature range that ensures the survival and growth of your plants. This range includes a minimum temperature threshold, an optimal temperature range, and a maximum temperature limit.

The minimum temperature threshold is the lowest temperature your plants can tolerate without suffering damage or death. For most winter crops, this threshold is around 45°F (7°C). However, more delicate tropical plants may require temperatures closer to 55°F (13°C).

The optimal temperature range for winter greenhouses typically falls between 60°F (15°C) and 70°F (21°C). This range ensures that your plants are comfortable and able to grow steadily throughout the winter.

On the other hand, the maximum temperature limit is the highest temperature your plants can withstand without being damaged by heat stress. This limit is usually around 85°F (29°C) for most winter crops.

Ideal Temperature for Common Winter Crops

Different winter crops have different ideal temperature ranges. Here are some examples of popular winter crops and their respective temperature preferences:

  • Leafy greens like lettuce, spinach, and kale prefer temperatures between 50°F (10°C) and 70°F (21°C). These crops can tolerate cooler temperatures but may suffer from slower growth if exposed to temperatures below 50°F (10°C).

  • Root vegetables such as carrots, beets, and radishes thrive in slightly cooler temperatures ranging from 40°F (4°C) to 60°F (15°C).

  • Brassicas like broccoli, cauliflower, and cabbage have similar temperature preferences to leafy greens, with an ideal range of 50°F (10°C) to 70°F (21°C).

  • Herbs like parsley, basil, and cilantro prefer temperatures between 55°F (13°C) and 75°F (24°C). These crops can tolerate slightly cooler temperatures, but growth may slow down if exposed to temperatures below 55°F (13°C).

  • Citrus fruits like lemons, oranges, and mandarins require a slightly warmer environment, with temperatures ranging from 55°F (13°C) to 85°F (29°C).

Challenges and Considerations for Extreme Cold

While winter greenhouses provide a controlled environment, extreme cold temperatures can still pose challenges for plant growth. Here are some considerations to keep in mind:

Protective Measures against Freezing

In regions with extremely cold temperatures, it’s important to protect your plants from freezing. Placing insulating materials around the base of your plants or using frost cloth can help shield them from the cold.

Using Heat Mats and Soil Warming Cables

Heat mats and soil warming cables can be used to provide direct warmth to the root zone of your plants. These heating methods are especially beneficial for cool-season crops that prefer slightly warmer soil temperatures.

Providing Supplementary Lighting

During the winter months, natural sunlight may be limited. Supplemental lighting, such as fluorescent or LED grow lights, can help provide the necessary light for plant growth.

Monitoring and Adjusting Temperature

Regularly monitoring the temperature in your winter greenhouse is crucial for the health of your plants. Use a thermometer to keep track of the temperature and make adjustments as needed to ensure it stays within the ideal range.

Common Heating Methods for Winter Greenhouses

To maintain the desired temperature in your winter greenhouse, various heating methods can be employed. Here are some commonly used heating options:

Electric Heaters

Electric heaters are a popular choice for winter greenhouses due to their ease of use and reliability. They can be controlled using a thermostat, allowing for precise temperature regulation.

Gas or Propane Heaters

Gas or propane heaters are another option for heating winter greenhouses. They provide efficient and consistent heat, but proper ventilation is crucial to prevent the buildup of harmful gases.

Wood-Burning Stoves

Wood-burning stoves provide both heat and ambiance to a winter greenhouse. They require a good amount of space and proper ventilation, making them more suitable for larger structures.

Radiant Floor Heating

Radiant floor heating involves heating the floor surface using electric or hydronic systems. This method provides consistent and even heat distribution, ensuring that plants receive warmth from their roots up.

Insulation Techniques to Maintain Optimal Temperature

Proper insulation is essential for maintaining optimal temperatures in a winter greenhouse. Here are some effective insulation techniques:

Double or Triple Glazed Windows

Double or triple glazed windows provide excellent insulation against cold temperatures. They create a layer of air that acts as a barrier, reducing heat loss and preventing cold drafts.

Bubble Wrap or Polyethylene Film Insulation

Bubble wrap or polyethylene film can be placed over windows to provide an additional layer of insulation. These materials trap air and help retain heat inside the greenhouse.

Thermal Blankets and Row Covers

Thermal blankets and row covers can be used to protect plants from freezing temperatures. These covers create a greenhouse within a greenhouse, trapping heat and providing extra insulation.

Insulated Panels or Rigid Foam Boards

Insulated panels or rigid foam boards can be installed on the walls and roof of a winter greenhouse. These materials provide excellent insulation, reducing heat loss and maintaining a stable temperature.

Maximizing Efficiency and Reducing Energy Costs

To maximize efficiency and reduce energy costs in your winter greenhouse, consider the following strategies:

Using Thermostats and Temperature Sensors

Thermostats and temperature sensors allow for precise control over the greenhouse temperature. Set the thermostat to maintain the desired temperature and use sensors to monitor temperature variations.

Utilizing Natural Heat Sources

Take advantage of natural heat sources, such as the sun during the day, to reduce reliance on heating systems. Orientate your greenhouse to capture as much sunlight as possible and use shading techniques to prevent overheating.

Applying Thermal Mass for Heat Storage

Thermal mass, such as water barrels or concrete floors, can absorb and store heat during the day, releasing it slowly at night. This helps stabilize the temperature inside the greenhouse and reduce energy consumption.

Proper Air Circulation and Humidity Control

Implementing fans for air circulation helps distribute heat evenly and prevents the formation of cold spots. Additionally, controlling humidity levels helps create a healthier environment for plants and reduces the risk of diseases.


Choosing the right temperature for a winter greenhouse requires careful consideration of plant types, climate, insulation techniques, and heating methods. By understanding the specific needs of your plants and implementing appropriate measures, you can create a thriving winter greenhouse environment. Remember to monitor temperature closely and make adjustments as needed to ensure optimal growth throughout the colder months.

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About the Author: Jake Scott