The ideal temperature to grow tomatoes in a greenhouse is between 70°F and 80°F during the daytime. But what temperature should a greenhouse be at night? Throughout the night, it’s well-advised to maintain the greenhouse temperature between 60°F to 65°F.

Keeping these temperatures ranges from daytime to nighttime will help you grow tomatoes with a high yield. However, keep in mind that both excessively high and low temperatures can also cause problems. Very high temperatures can yield unmarketable tomatoes, while very low temperatures can affect your plants’ health. 

Daytime temperatures

Tomatoes will grow effectively at a daytime temperature between 70°F to 80°F. This range is because the light conditions outside will determine which end you should use in the greenhouse. Simply put, you should go as low as 70°F on a cloudy day, and then go up as 80°F on a clear day. 

Depending on your region, you get the idea of how to determine which end of the range is appropriate for the day. Just to expand on it, the low range is best on a cloudy day because of the low light intensity and high temperature in that condition. Therefore, the tomatoes will also have a lower rate of photosynthesis. 

On the contrary, bright days require you to put the greenhouse temperature at the high end of the range because of the high light intensity. In some regions, you can even go as high as 85°F. The bottom line is to use the light conditions as your deciding factor for the daytime temperature adjustment in the greenhouse.

Nighttime temperatures

During the nighttime, the greenhouse’s ideal temperature range should be between 60°F to 65°F. Remember that tomatoes, in particular, are more sensitive to cool temperatures compared to other crops. So at night, you mustn’t go lower than 60°F if you want to avoid pollination and fruit development problems. 

What happens when the temperature is too high in the greenhouse

When your greenhouse temperature gets too high, it can affect the development of your tomato fruits. This is especially critical when it’s very warm outside, and your greenhouse exceeds 95°F. You’ll risk abnormal color development on your fruits, and you’ll delay the plant’s root growth. 

What happens when the temperature is too low in the greenhouse

Having a very low temperature in the greenhouse is also as influential for growing tomatoes. If the greenhouse reaches a temperature below 60°F, you run the risk of nutrient deficiencies in your plants. As a result, they become more susceptible to growth abnormalities and fungal infections. 

How To Maintain The Ideal Temperatures For Growing Greenhouse Tomatoes

It’s crucial to maintain the ideal temperatures from daytime to nighttime in your greenhouse. You can achieve this by using a thermostat, effective ventilation system, alternate heating system, evaporative cooling system, and modifying the greenhouse roof.

Using a thermostat

Having a thermostat will give you an idea if your greenhouse maintains the ideal temperature for the tomatoes. It’s best that you place it at the plants’ blossom height or near the center of the greenhouse for efficient control over the temperature. Check the thermostat several times throughout the day, especially during the times when the temperature outside gets very high. 

To make sure you’re getting an accurate reading, examine the placement of the thermostat as well. The sun should not be hitting it directly, or otherwise, it will read a higher temperature. Put it in a shaded area or inside an aspirated box for an accurate reading. 

Effective ventilation system

In addition to using a thermostat, the greenhouse should also have an effective ventilation system to keep the temperatures under control. You have the option to use side vents or automated roof systems to maintain the proper air circulation in the greenhouse. The decision lies to whether you want to open the vents when needed manually, or if an automated system is more convenient for you. 

Overall, you want an effective ventilation system for air exchange and air circulation to prevent condensation and fungal growth. At the same time, ventilation affects the humidity of the greenhouse. Make sure you’re consulting a professional when it comes to the installation of your ventilation system. 

Alternate heating system

A common alternate heating system for greenhouses that grow tomatoes is the use of heating pipes. This system is particularly useful if you want to heat your greenhouse from the base. The pipes warm the air at ground level, which then forces cool air at the top of the greenhouse to go downward. 

Evaporative cooling system

If you need to cool the greenhouse, an evaporative cooling system is your best solution. This is because it uses water for cooling the air, which also makes a moist and humid environment. If you live in an area 

where it gets very dry, an evaporative cooling system will help in keeping your plants healthy. 

Modifying the greenhouse roof

You can increase the greenhouse’s roof height if you live in a region where the climate gets very hot. This way, you’ll be able to protect the tomatoes from the harsh heat. Remember that while tomatoes hate very cold conditions, uncontrolled high heat can also be as detrimental for their growth. 

Ideal Humidity To Grow Tomatoes In A Greenhouse

The ideal humidity to grow tomatoes in a greenhouse is between 60 to 70 percent. Keeping your greenhouse humidity in this range will help you prevent mold growth and other diseases. Humidity also plays a role in regulating the greenhouse temperatures, so check your ventilation system regularly. 

Ventilation is especially essential during cool, cloudy mornings. Drying the plants by heating or ventilating will control leaf mold and replenish the carbon dioxide that the plants need. And lastly, proper control of humidity can help reduce heating and cooling costs in your part. 

How Do You Grow Tomatoes In A Greenhouse Year-Round

You can grow tomatoes in a greenhouse year-round if you consider the tomato variety, season, feeding, and watering beforehand. Unlike with field growing, using a greenhouse can extend the growing season of your tomatoes. However, failing to execute a plan according to these factors will give you a hard time achieving a year-round production. 

Tomato variety

Similar to when you’re growing tomatoes outdoors, you have to know what varieties would be suitable in an indoor environment. It sounds complicated, but it’s as simple as choosing the seeds marked as “greenhouse variants.” They are so-called because they are built to tolerate the conditions of indoors instead of your typical garden varieties. 

For greenhouses, you want vine or cordon tomatoes. The most popular and widely-used indoor tomato variety in the United States is called Trust. There are also Dutch hybrids called Match, Switch, and Blitz that are all worthy considerations for indoor growing. 

 

How long will a tomato plant live in a greenhouse

A tomato plant will live in a greenhouse for years as long as the conditions are ideal. The reason behind this indefinite lifespan is because greenhouse varieties of tomatoes are indeterminate, so they continuously produce flowers and fruits as they grow. They can grow several meters long and can produce over a long harvest season. 

Season 

Growing tomatoes in a field meant planting the seeds before the last frost of the year. But with greenhouse tomatoes, you can seed a fall crop and a spring crop in early June and December, respectively.  Depending on the location, you can have up to two tomato crops during the year, as long as you maintain ideal conditions inside.

Can you grow tomatoes in a greenhouse in winter

You can grow tomatoes in a greenhouse in winter because greenhouses are able to trap the heat from the sun’s radiation and then keep it inside. However, be aware that the heat inside is only relative to how cold it is outside. The solution is supplementing heat, and you’ll still be able to experience an increase in yield with your greenhouse tomatoes during winter. 

When can tomatoes go in an unheated greenhouse

You can plant tomatoes in your unheated greenhouse after the last frost date has passed. Why after the last frost date? Any temperature lower than 50°F will affect the germination and growth of your seeds. 

 

It’s best that you wait until your region’s last frost date has passed to ensure good outcomes. Unlike in a heated greenhouse, your tomatoes are more at risk of the damages caused by environmental changes. Therefore, knowledge of your region’s condition and timing are essential for success. 

Feeding 

Once you transplant the tomatoes into their final pot, you can start fertilizing. How often do you feed tomatoes in a greenhouse? Feed your growing tomatoes every one or two weeks with a nitrogen-rich liquid fertilizer. 

Once you see fruits, you can switch to using a tomato fertilizer. Remember to follow the instructions of the fertilizer to know how often you should feed your plants. You also want to skip feeding twice during the tomato plant’s life cycle if you use liquid fertilizer to prevent the accumulation of salts. 

Watering

A greenhouse tomato plant requires up to 3 quarts of water per day. Make sure you’re watering your plants at regular intervals, and it can be more often in a hotter climate. However, do note that tomato leaves are sensitive, so avoid using overhead irrigation for watering. 

You’ll know that your plants are not getting enough water if their leaves are wilted and dark green. On the contrary, yellow leaves mean that you are overwatering your tomatoes. Make sure the soil of your plants is moist and not dry or soggy. 

Do Tomatoes Grow Better In A Greenhouse

Tomatoes grow better in a greenhouse because of the extension of the growing season, protection against temperature and weather changes, and safe growing environment. Greenhouse tomato farming has been rising since the mid-1990s because these advantages solve the quality inconsistencies in field tomato farming. As a result, consumers also had an increasing preference for greenhouse tomatoes. 

Extension of the growing season

Tomatoes can be picky plants, so it’s typical for field growers to have a shorter growing season depending on their region. Using a greenhouse eliminates this drawback because you don’t have to stop growing your tomatoes once the summer months are over. Growing tomatoes in the greenhouse give you the advantage of extending your harvest season until late fall. 

Protection against temperature and weather changes

Growing tomatoes indoors will protect the plants from the erratic temperature and weather changes outside. Infield farming, you have no control over the harsh heat, wetness from rain, and fluctuations in temperature. As a result, the tomatoes become more vulnerable to diseases and other conditions when they’re outside. 

Safe growing environment

Besides protection from temperature and weather changes, the greenhouse also makes a safe growing environment for the tomatoes. Its structure will make it impossible for predators like birds, rodents, and large mammals to access the plants. The enclosed environment will also deter anyone from causing potential damages to your crops. 

Bottom Line

The ideal temperature to grow tomatoes in a greenhouse is between 70°F to 80°F during daytime and between 60°F to 65°F during nighttime. At daytime, it’s best to stick to the low end of the range when it’s cloudy, and then use the temperature at the high end if the weather is clear. These adjustments are to ensure that your tomatoes will be able to photosynthesize efficiently, regardless of the condition. 

Maintaining your greenhouse temperature in these ranges from daytime to nighttime is crucial for your tomatoes’ growth and health. If the greenhouse temperature gets too high, the quality of the fruits and root growth will be affected. On the other hand, letting the greenhouse temperature get too low puts your tomato plants at risk for nutrient deficiencies and fungal infections. 

Using a thermostat, effective ventilation system, alternate heating system, evaporative cooling system, and modifying the greenhouse roof are the ways to maintain the greenhouse’s ideal temperatures. Simultaneously, you must monitor the greenhouse humidity because it plays a significant role in regulating the greenhouse temperature.