What Temperature Should A Greenhouse Be

What Temperature Should A Greenhouse Be? The Ultimate Guide

It’s a crisp winter morning, and as I step into my greenhouse, a wave of warmth greets me. I see rows of thriving vegetables, colorful blooms, and lush foliage. For a moment, I forget about the snow outside, knowing that my little haven is a haven for my beloved plants.

This is the magic of maintaining the ideal temperature in a greenhouse. As a passionate gardener, I’ve witnessed firsthand how temperature control can turn a humble greenhouse into a flourishing oasis, providing fresh produce and vibrant blooms even in the harshest weather conditions.

In the summertime, I’ve found that the ideal greenhouse temperature ranges from 75-85°F during the day to 60-76°F at night. These numbers are like the sweet spot for my plants, where they bask in the warmth of the day and enjoy slightly cooler nights.

As the seasons transition to winter, the temperature requirements shift. During the day, I aim to maintain a range of 65-70°F, providing a comfortable environment for my green companions. At night, a slightly cooler 45°F is ideal to ensure they get the rest they need.

Why Greenhouse Temperature Matters

Why Greenhouse Temperature Matters

As a greenhouse enthusiast, I’ve come to appreciate that understanding why greenhouse temperature matters is the bedrock of successful gardening within these controlled environments. It’s not just about maintaining a pleasant atmosphere; it’s about recognizing that temperature is the lifeblood of our plants’ well-being. Maintaining the right temperature within greenhouses is crucial for ensuring the best possible growth and productivity of plants.

Think about it this way: Imagine you’re in your favorite room, snug and comfortable. Suddenly, you’re thrown into extreme heat or a freezing cold space. Your comfort vanishes, right? Well, it’s similar for plants. They have their comfort zones, and when we respect those, they thrive. The temperature range is like their sweet spot – it’s where they feel most at home.

Temperature isn’t just a number; it’s a fundamental factor in the life of a plant. It influences almost every facet of their existence. From the energy-producing magic of photosynthesis to their ability to breathe (yes, plants respire too!), and even their capacity to fend off pests and diseases – it’s all tied to temperature. Keeping this range stable is akin to ensuring our plants live in the perfect neighborhood, where they have everything they need at their fingertips.

But here’s the real treasure: extending the growing season. By maintaining the right temperature, we can continue to enjoy fresh produce, even when the world outside is freezing or scorching. For those of us who revel in a lush harvest, this can make all the difference in the world.

Additionally, think of temperature control as a fortress for your plants. Unpredictable weather can wreak havoc, causing frostbite or heat stress. With precise temperature management, we provide a protective cocoon for our plants, shielding them from Mother Nature’s mood swings.

Here are five valuable tips to ensure the proper maintenance of greenhouse temperatures I follow:

Right-size Your HVAC System: I’ve learned that sizing my HVAC system correctly is absolutely vital, especially for indoor grow rooms. It’s all about handling the heating and cooling needs that come with cultivating plants indoors. Striking the right balance between air temperature, circulation, and dehumidification can be quite a task, especially when I’m trying to maximize plant density in each room.

Ensure Sufficient Heating and Cooling Capacity: For greenhouse production, I’ve realized the importance of having enough heating capacity to combat the challenges of winter. It’s more efficient to heat beneath the crop. Equally critical is having the right cooling capacity to tackle scorching summer weather. Whether I rely on natural ventilation, fan-assisted ventilation, or pad and fan cooling, I make sure my setup can handle the hottest days and maintain the desired growing temperatures.

Install Horizontal Air Flow (HAF) Fans: Particularly in my indoor grow rooms, I’ve found HAF fans to be absolute essentials. They work wonders for enhancing air circulation, ensuring a more uniform distribution of temperature within the crop. HAF fans also prevent those pesky microclimates from forming around leaves, which not only promotes better gas exchange but also helps control issues like powdery mildew. I always make it a point to steer clear of “dead air” zones—those areas without airflow within my growing space. I’ve also learned that fan placement is key to effectively managing moisture levels.

Utilize Shade Curtains: When dealing with intense light and high temperatures, I rely on shade curtains. These curtains are designed to reduce light intensity by around 30% to 50%, and I close them during the sunniest and hottest parts of the day. If my structure lacks retractable shade curtains, I’ve even used whitewash on the greenhouse roof as a temporary shade curtain. It can easily be washed off when the fall season approaches.

Accurate Temperature Measurement: When it comes to measuring temperature, I’ve found it crucial to place my environmental control sensors closer to the crop and in the center of the growing area. Tracking temperature consistently over a 24-hour period—what we call average daily temperature—is key for optimal plant growth. Additionally, I use a digital infrared thermometer to measure leaf temperature, helping me determine precisely when to close the shade curtain.

These practical tips have been instrumental in my journey to maintain the ideal temperatures in my greenhouse, ensuring my plants stay healthy and thrive throughout the entire growing season.

Optimal Temperature Ranges for Different Plants

Optimal Temperature Ranges for Different Plants

As someone deeply passionate about greenhouse gardening, I’ve come to appreciate that one of the most crucial aspects of success lies in understanding the specific temperature preferences of the plants we nurture. It’s akin to knowing the unique needs of your closest friends – it enables you to provide the best care possible.

Just as we humans have our comfort zones when it comes to temperature – some prefer a warm and sunny beach day, while others thrive in cooler climates – our beloved plants are no different. They each have their own ideal temperature ranges in which they flourish, and by catering to these preferences, we can unlock their full potential.

Whether you’re cultivating delicate herbs like basil and parsley, hardy vegetables such as tomatoes and cucumbers, or exotic flowers with intricate needs, understanding their optimal temperature ranges is akin to holding the key to a secret garden.

By mastering the art of providing the right climate, we can foster conditions where growth, health, and productivity are maximized. Imagine luscious, aromatic herbs that thrive year-round or tomato vines laden with plump, juicy fruit – it’s all within your reach once you grasp these temperature secrets.

Understanding And Applying Specific Temperature

Optimal Growth Conditions:

As a devoted greenhouse gardener, I’ve learned that understanding temperature preferences is akin to being a gracious host for a diverse group of guests. In my greenhouse, each plant species is like an individual with its own comfort zone. For instance, beloved herbs like basil and thyme thrive when the mercury hovers between 70 to 85°F (21 to 29°C). It’s as if these temperatures unlock their aromatic oils, resulting in lush foliage and rich flavors. Meanwhile, leafy greens like lettuce and spinach prefer cooler conditions, ideally between 45 to 75°F (7 to 24°C). By respecting these preferences, I create an environment where each plant can truly shine.

Faster Germination and Seedling Growth:

When it comes to germination and nurturing young seedlings, temperature control becomes my way of providing the perfect nursery. I’ve noticed that different plants have specific temperature ranges that boost their growth. For instance, tomato seeds thrive in temperatures around 70 to 75°F (21 to 24°C), while peppers prefer it a tad warmer at 75 to 80°F (24 to 27°C). By maintaining these conditions, I give my plants a strong start, allowing them to develop robust root systems and sturdy stems. This, in turn, sets the stage for more productive and resilient mature plants.

Flowering and Fruit Production:

In my greenhouse, it’s not just about growing plants; it’s about orchestrating a symphony of growth. Fruit-bearing plants, like tomatoes, peppers, and cucumbers, often have specific temperature requirements for optimal flowering and fruit set. For example, tomatoes tend to set fruit best when daytime temperatures hover between 70 to 75°F (21 to 24°C), with nighttime temperatures above 50°F (10°C). 

Disease and Pest Resistance:

Temperature control also acts as my greenhouse’s immune system. Some plants are more prone to pests or diseases at specific temperature extremes. By keeping the greenhouse within the optimal range for each plant, I reduce the chances of pest infestations and minimize disease risks. It’s like giving my plants a fortified defense system, ensuring they stay healthy and vigorous.

Extended Growing Season:

One of the most rewarding aspects of greenhouse gardening is the ability to extend the growing season. It’s like having a magical time machine that keeps my garden producing year-round. By adjusting temperatures, I can start planting earlier in the spring and continue later into the fall or even throughout the winter. This means a constant supply of fresh produce and vibrant blooms, creating a greenhouse that truly never sleeps.

Energy Efficiency:

I’m also a firm believer in efficient energy use. Much like optimizing my home’s heating and cooling system, I ensure that the greenhouse only expends energy where necessary.

Drawing from a recent grower survey, it is estimated that a standard greenhouse employs supplemental lighting for approximately 3.25 hours each day, with variations by season (9 hours in winter, 2 hours in fall and spring, and none during summer). For this level of LED lighting, the annual cost is calculated as follows: 0.12 (cost per kWh) * 3.25 (hours per day) * 365.25 (days in a year) * 600 (wattage per light) / 1000 (conversion to kilowatts) = USD 85.47 per light annually.

Considering a one-hectare greenhouse requires around 1200 lights, the total annual cost for lighting would amount to USD 102,562.

I’m not wasting resources by heating or cooling the entire space uniformly. Instead, I’m focusing my efforts where they matter most. This not only reduces energy costs but also lessens my environmental impact, aligning my gardening practices with a sustainable ethos.


Can a greenhouse be cold?

Yes, a greenhouse can become cold, especially during winter or at night. Temperature control is crucial to maintain optimal conditions for plant growth.

Why are my plants dying in my greenhouse?

Several factors can contribute to plant issues in a greenhouse, including inadequate temperature control, overwatering, poor ventilation, or pest infestations. Careful observation and adjustments can help address these problems.

Can a greenhouse overheat?

Yes, a greenhouse can overheat, especially during hot weather or due to excessive sunlight. Proper ventilation, shading, and cooling systems are essential to prevent overheating.

How do I keep my greenhouse warm?

To maintain warmth, use insulation, heaters, and thermal curtains, and consider the greenhouse’s orientation. Monitoring and adjusting temperatures regularly are also crucial.

Is it hot inside a greenhouse?

Yes, greenhouses can become hot, particularly in sunny weather. Temperature management is vital to prevent heat stress on plants.

How do I keep moisture in my greenhouse?

To maintain moisture levels, consider using damp gravel trays, misting systems, and water sources like large containers. Properly water your plants and maintain humidity.

Do greenhouses need humidity?

Yes, some level of humidity is essential in greenhouses, as it helps plants thrive. However, excessive humidity can lead to issues, so maintaining the right balance is crucial.

How do you control moisture in a greenhouse?

Controlling moisture involves proper watering practices, adequate ventilation, and using humidity trays or misting systems. Monitoring moisture levels is key to preventing issues.

Do greenhouses need ventilation?

Yes, greenhouses require ventilation to regulate temperature, humidity, and air circulation. Adequate ventilation prevents overheating and maintains optimal growing conditions.

How do you use a greenhouse for beginners?

For beginners, start with easy-to-grow plants, learn temperature and watering requirements, and maintain a regular gardening schedule. Gradually experiment with more plant varieties as you gain experience.

What does a greenhouse need?

A greenhouse needs proper temperature control, ventilation, watering systems, suitable growing medium, and adequate sunlight. Tailor these elements to the specific needs of your plants.

Do greenhouses need heaters?

In colder climates, heaters are essential to maintain a consistent temperature, especially during winter. Heating systems can be crucial for year-round cultivation.

What is the cheapest way to heat a greenhouse?

The cheapest way to heat a greenhouse includes using passive solar heating, thermal mass, insulating materials, and considering energy-efficient heating options like propane or electric heaters with proper insulation.

Final thought:

So, what temperature should a greenhouse be? The answer, my fellow gardeners, is a personal one, dictated by the unique needs of your cherished plants. It’s about listening to the whispers of nature, observing the dance of sunlight, and understanding the subtle cues that your garden offers.

Remember that it’s not just about temperature; it’s about creating an environment where the magic of growth unfolds before your eyes. It’s about nurturing life, celebrating diversity, and reaping the bountiful rewards of your labor.

So, set your thermostats, open your vents, and adjust your shades with purpose and care. Your greenhouse awaits, ready to be your canvas for botanical artistry, your sanctuary for tranquility, and your source of endless wonder. May your greenhouse be a place where the temperature is not just a measure of warmth but a testament to your dedication as a gardener?

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