Ideal Greenhouse Temperature

Ideal Greenhouse Temperature! Mastering the Art of Plant Growth

An ideal greenhouse temperature typically falls between 65°F to 75°F (18°C to 24°C) during the day, with a nighttime decrease of around 10-15 degrees Fahrenheit (5-8 degrees Celsius) being acceptable for many plants. However, plant-specific needs vary: warm-season plants like tomatoes and peppers thrive in temperatures of 70°F to 85°F (21°C to 29°C) during the day, while cool-season crops such as lettuce and spinach prefer a range of 55°F to 70°F (13°C to 21°C). 

Maintaining consistent temperatures is crucial for healthy growth, and growers often use ventilation, heating, shading, and cooling systems to regulate the climate. 

How do temperatures impact plant growth?

How do temperatures impact plant growth

These temperature influences on different plant types and growth stages help growers create optimal conditions for cultivation.

Optimal temperature range for various plant types:

Different plants have specific temperature ranges within which they thrive best. For example:

Cool-season crops like lettuce, spinach, and kale generally prefer temperatures between 45°F to 75°F (7°C to 24°C) for optimal growth.

Warm-season crops such as tomatoes, peppers, and cucumbers thrive in temperatures ranging from 70°F to 90°F (21°C to 32°C).

Tropical plants like orchids or certain exotic fruit trees might require higher temperatures, often above 80°F (27°C).

Each plant species may have specific temperature preferences for different growth stages, such as seed germination, vegetative growth, and flowering/fruiting.

Effects of temperature on plant growth stages

Seed germination often requires specific temperature ranges. Some seeds germinate best in cooler temperatures (e.g., lettuce), while others require warmer conditions (e.g., tomatoes).

Optimal temperatures during this stage promote healthy leaf and stem development, influencing plant size and structure.

Temperature fluctuations can significantly impact flowering and fruit set. High temperatures might affect pollen viability and reduce fruit production, while low temperatures can hinder flower formation and fruit development.

Impact of temperature extremes on plants

Excessive heat can lead to heat stress, causing wilting, reduced photosynthesis, and in extreme cases, tissue damage or death. It can also increase water requirements, leading to drought stress.

Cold stress can cause slowed growth, leaf discoloration, frost damage, and in severe cases, frostbite or freezing of plant tissues, resulting in cell damage and death.

Rapid changes in temperature, especially from warm to cold or vice versa, can shock plants, weaken their immune systems, and make them more susceptible to diseases and pests.

What factors affect greenhouse temperature?

Knowing and handling these things outside and inside the greenhouse are really important for plant growers. It helps them keep the best and steady conditions for plants to grow well. Also, it helps in reducing the impact of extreme temperatures all year round.

External environmental factors

Sunlight intensity and duration

Sunlight is a primary factor influencing greenhouse temperatures. The angle of sunlight, duration, and intensity throughout the day impact how much heat is absorbed by the greenhouse.

The angle of incidence varies based on the season and geographical location, affecting how sunlight enters the greenhouse. In winter, the sun’s angle is lower, reducing direct sunlight exposure and heat gain compared to summer.

Seasonal variations

Seasonal changes significantly affect greenhouse temperatures. In winter, shorter daylight hours and lower sun angles lead to decreased heating potential, while summer brings longer days and higher sun angles, potentially causing overheating.

Managing temperature variations across seasons is crucial for maintaining optimal conditions for plant growth.

Climate and geographical location

Geographical location determines the overall climate and weather conditions experienced by a greenhouse. Regions with different climates face varying temperature ranges, humidity levels, and sunlight patterns.

Coastal areas may experience more moderate temperatures due to oceanic influences, while inland regions might have more extreme temperature fluctuations.

Internal factors

Heating and cooling systems

Heating systems (e.g., boilers, and radiant heaters) help maintain warmth during colder periods, ensuring plants stay within their optimal temperature range.

Cooling systems (e.g., fans, evaporative cooling) are essential in hotter climates or during summer months to prevent overheating, maintain a comfortable temperature for plant growth.

Insulation and ventilation

Proper insulation helps regulate internal temperatures by minimizing heat loss during cold periods and preventing excessive heat gain during warm periods.

Ventilation systems, including windows, louvers, or exhaust fans, facilitate airflow and regulate humidity levels, preventing the buildup of excess heat and moisture.

Thermal mass within the greenhouse

Thermal mass refers to materials (e.g., water barrels, and concrete floors) that can absorb, store, and release heat slowly, helping to stabilize temperature fluctuations within the greenhouse.

Water, in particular, has high thermal mass and can be strategically placed to regulate temperature variations by absorbing excess heat during the day and releasing it at night.

How to regulate greenhouse temperature effectively?

How to regulate greenhouse temperature effectively

Using both simple methods and more active ways to control temperature helps growers make a steady and controlled space in the greenhouse. This helps plants grow well in various seasons and weather types.

Passive temperature regulation techniques

Insulation materials

Insulation materials such as polyethylene film, double-layered greenhouse covers, or bubble wrap help trap heat within the greenhouse by reducing heat loss through conduction and radiation.

Using materials with high insulation properties on walls, floors, and roofs helps maintain stable temperatures, especially during colder periods.

Shading and reflective surfaces

Shading techniques involve applying shade cloths or using retractable screens to reduce the amount of direct sunlight entering the greenhouse, particularly during peak sunlight hours. 

This prevents overheating.

Reflective surfaces, such as reflective paints or films on greenhouse surfaces, help bounce off excess sunlight, reducing heat absorption and maintaining cooler temperatures inside the greenhouse.

Active temperature control methods

Heating systems

Heating systems are essential during colder seasons or in regions with low temperatures to maintain the required warmth for plants. Common heating methods include:

  • Radiant heaters: Emit heat directly to objects and plants, offering efficient and targeted heating.
  • Geothermal heating: Utilizes the consistent temperature of the earth to provide heating, typically through pipes buried underground.
  • Boiler systems: Circulate hot water or steam through pipes to maintain greenhouse temperatures.

Cooling systems

Cooling systems are crucial for managing high temperatures, especially during summer or in warmer climates. These systems help dissipate excess heat to maintain optimal conditions for plant growth. Examples include:

  • Fans and ventilation: Circulate air inside the greenhouse, preventing heat buildup and maintaining airflow.
  • Evaporative cooling: Uses the principle of water evaporation to reduce temperatures. Systems like misting or pad and fan systems help lower temperatures by evaporating water into the air.

Automation and smart technologies for temperature control

Automation systems integrate various sensors and controls to manage temperature, humidity, and ventilation automatically.

Smart technologies use data-driven algorithms to regulate heating, cooling, and ventilation systems based on real-time conditions, optimizing energy efficiency and maintaining ideal growing conditions.

Sensors for temperature, humidity, and light can trigger automated actions, adjusting systems as needed to maintain the desired climate.


What should the air temperature be in a greenhouse?

The air temperature in a greenhouse typically ranges between 70°F to 80°F (21°C to 27°C) during the day and can drop by about 10 to 15 degrees Fahrenheit at night.

What is the best temperature and humidity?

The best temperature varies based on plant types but generally falls within 65°F to 75°F (18°C to 24°C), accompanied by a humidity range of 50% to 60% for most plants.

What temperature should I heat my greenhouse in winter?

During winter, it’s recommended to maintain a minimum temperature of around 55°F to 60°F (13°C to 16°C) to protect plants from freezing.

Is 70% humidity very high?

A humidity level of 70% is relatively high but can be suitable for certain plants, while for others, it might be excessive.

Is 70% humidity high or low?

A humidity level of 70% is considered high and may require adjustments, depending on the specific needs of the plants being grown.

Is 30% humidity hot?

A humidity level of 30% is relatively low and might feel dry. However, temperature combined with humidity determines the perceived comfort or discomfort.

Final Words

The best temperature for plants in a greenhouse is usually between 65°F to 75°F during the day, and it’s okay if it gets cooler by 10-15 degrees at night. But different plants like different temperatures.

Temperature really matters for how plants grow. It affects how seeds start growing, how the plant gets bigger, and even how it flowers and makes fruit. If the temperature goes up or down too much, it can stress the plants out, and they won’t grow well.

Things like how sunny it is, the time of year, and where the greenhouse is located affect its temperature. Inside the greenhouse, stuff like heaters or fans, insulation, and how the air moves around also make a big difference in how warm or cool it gets

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