Will a Greenhouse Burn Your Plants?

Greenhouses are wonderful inventions. But due to their glass paneling and the heat they trap, you might wonder if your plants are safe in the greenhouse during summer. Should you be worried about your greenhouse burning your plants? 

A greenhouse can burn your plants though it’s unlikely since a greenhouse’s paneling is meant to filter harmful UV light and promote plant growth. However, your plants can get too hot and die during summer due to excessive heat in your greenhouse. 

In the rest of this article, I’ll discuss if greenhouse plants can burn, what temperature your greenhouse should be, how to cool it down when it gets hot, and whether you can keep plants growing in your greenhouse all summer. Keep reading to learn more about controlling greenhouse temperatures in the hot sun.

Will a Greenhouse Protect Plants From Sunburn?

Greenhouse science can be a bit confusing as you would think the sun would easily scorch your poor plants. I mean, it’s possible to start a fire using only a magnifying glass and some sun. However, the answer to the greenhouse sunburn question just might surprise you. 

A greenhouse will usually protect plants from sunburn since the glass or paneling used is meant to filter the intense UV rays from the sun. However, if you live somewhere extremely warm and your greenhouse is always under the sun and has poor ventilation, your plants may still overheat.

So, as you can see, your greenhouse plants generally have more protection from the harsh sun than your outdoor plants. However, if you live somewhere that experiences extreme temperatures, you may want to consider adding some shade to your greenhouse to help your plants. 

What Temperature Is Too Hot for Plants in a Greenhouse?

You now understand how greenhouse glass functions and that your plants are generally safe from sunburn. Next, let’s talk about plants overheating. Sunburn and overly warm plants are two different things, but both can be deadly. 

Any temperature over 90°F (32°C) is too hot for plants in a greenhouse. Typically, a greenhouse should be kept at about 80°F (27°C) as this is the temperature at which most plants thrive. Proper ventilation and humidity are essential to keep your greenhouse’s temperature lower during summer. 

It’s essential to install a thermometer in your greenhouse to help you monitor the temperature changes throughout the year. I recommend using a thermometer that monitors humidity and connects directly to your phone to notify you when there’s a sudden shift in temperature.

How To Cool Down Your Greenhouse

A greenhouse can quickly get too warm during the summer months and cause your plants to wilt or die. So it’s essential that if you notice signs of your plants overheating that you act quickly. Plants are pretty expressive and will immediately display signs of stress due to the inadequate temperature in the greenhouse. 

Signs your plants are too hot:

  • Wilting
  • Bolting
  • Dry leaves
  • Crunchy leaves 
  • Yellowing
  • Discoloration

These are the most common signs plants will display if they get too warm. So if you notice any of these signs in your greenhouse plants, you should act quickly. Luckily there are several ways for you to drop your nursery’s temperature back to an acceptable level. 

Ways to cool down your greenhouse:

  • Install proper ventilation. In order for your greenhouse to function correctly, it needs ventilation. Typically you can find vents along the top or sides of your greenhouse, which you can open to allow excess heat to escape and fresh air to circulate. 
  • Add shade. Adding shade is a great way to ensure your greenhouse’s temperature drops. You can do this with tarps or special plant shade cloths that will still allow some light through. 
  • Raise the humidity. You can do this by damping down the inside of your greenhouse, the concrete, and the walls. This method is great for raising the humidity and lowering your greenhouse’s temperature. 
  • Check your insulation. Poor insulation can allow humidity to escape, which can significantly raise your greenhouse’s temperature. It’s always a good idea to inspect your structure for possible holes and patch them up. 
  • Install fans. Fans are a great way to help quickly circulate the air in your greenhouse and thus bring down the sweltering temperature. 
  • Water your plants regularly. Damp soil is another great way to drop hot temperatures in a greenhouse. However, you should always be careful of overwatering and too much humidity, as these can be just as harmful as excessive heat. 
  • Use mulch. Mulch is an excellent way to lock moisture into the soil and prevent your plants from drying out on hot days. Mulch will also help you to maintain your humidity and thus a lower overall temperature in your greenhouse. 
  • Install misters. If you’re looking for a more automated form of cooling, your greenhouse misters are always a good option. Misters can help with watering and can be put on a timer or turned on from your phone. 
  • Add an air conditioning unit. You’ll find many portable air conditioners on the market. Consider this method if you experience frequent excessive heat in your greenhouse. 
  • Grow large leafy plants. How you plant your garden matters. By planting large plants with giant leaves, you can better provide shade to the more sensitive plants, such as greenhouse cucumbers.
  • Monitor your greenhouse’s temperature regularly. During the summer months, you should check your thermometer consistently in order to gauge the heat in your greenhouse. Doing so will allow you to act more quickly if you notice a sudden change. 

As you can see, there are quite a few cooling options for your greenhouse, many of which are relatively easy to implement. Of course, it’s always best to start with good ventilation. You can then work from there. If you struggle to maintain a cool temperature for your greenhouse, consider moving your structure somewhere with partial shade

Plant Heat-Resistant Plant Varieties

If you’re constantly dealing with sweltering hot temperatures in your greenhouse, another good idea is only to plant heat-resistant varieties of plants. Doing this will ensure your plants survive even if the temperatures dip a little too high.

Just be sure to get the temperature back down within a reasonable period, or your plants will eventually die from the heat. 

Can You Keep Plants in a Greenhouse All Summer?

The steps for cooling down a hot greenhouse are pretty simple, and there are plenty of things you can try. However, you might wonder if it is worth all the hassle to try and keep your plants alive when it is hot. Can you actually keep plants in a greenhouse all summer? 

You can keep plants in a greenhouse all summer so long as you provide adequate temperatures, moisture, health, and nutrients. If you live somewhere warm, you’ll need to do your best to maintain temperatures under 90°F (32°C) so your plants don’t bolt and die. 

Some plant varieties can be very sensitive to heat and easily stressed, while others will hardly react to the change in temperature. Ultimately whether your plants will thrive during the summer months is entirely up to factors such as:

  • The weather in your area
  • How much sun your plants are getting
  • The humidity in the air
  • The variety of plants you’re growing

Fortunately, there are ways to combat these issues, but it will take some work. Proper insulation and ventilation are probably the most critical factors in keeping greenhouse plants alive through summer. 


A greenhouse is a great addition to your garden, but it could technically burn your plants, especially if you live somewhere very warm. 

While the paneling on greenhouses is meant to filter the sun’s UV rays and be less harsh for plants, keeping proper temperatures during the summer months can be challenging. Excessive heat will result in the death of plants. 

However, you can combat excessive heat by ensuring proper ventilation, insulation, and humidity.

But suppose you’re struggling to maintain a cool temperature for your greenhouse, consider moving your structure somewhere with partial shade. 

Alexander Picot

Alexander Picot is the principal creator of TheGrowingLeaf.com, a website dedicated to gardening tips. Inspired by his mother’s love of gardening, Alex has a passion for taking care of plants and turning backyards into feel-good places and loves to share his experience with the rest of the world.

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