45° in the greenhouse this summer, how to avoid it, and what consequences on the plants?

Summer is finally here with these longer days, but also with its very hot temperatures. We hear it everywhere, in France, summers will be increasingly hot with episodes of heat waves. If you never say no to a little heat, your plants in the garden and vegetable patch may suffer. But not only that. When you have a greenhouse, the temperature can rise so high and so quickly that you could be in for some nasty surprises. And managing the temperature of a greenhouse is essential to keeping your plants healthy. So how can you protect your plants, how can you prevent the temperature from rising too high? Some tips to avoid being surprised by the heat.

Why does my greenhouse get so hot?

A question that may seem simple, but how does the air in my greenhouse heat up? Well, thanks to the “greenhouse effect”. To put it simply, this effect that everyone has heard about is, in fact, a natural phenomenon. The greenhouse lets the sun's rays pass through, which are absorbed by the plants and converted into thermal energy. Heat stays in the structure because the walls slow heat loss. So, it will necessarily be warmer in the greenhouse rather than outside. To know the interior temperature of your greenhouse, you can place a thermometer there so you can ensure that the heat does not exceed 32°C.

How to avoid extreme heat in the greenhouse?

Fortunately, there are several solutions for removing heat from your greenhouse. If you have opted for a greenhouse that has windows and doors then nothing could be simpler, you will need to open them as much as possible in order to create a current of air which will certainly cool the interior of your greenhouse. If you are going on vacation and you are worried about your plants, there are automatic opening systems. A real plus when you can't always check what's happening in your greenhouse.

Choose a bright site for the greenhouse and provide adequate ventilation. Suitable shading can help reduce overheating in strong sunshine. The temperature reduction depends on the weather, ventilation and structure. Crops still need enough light; opaque walls are not a general solution.

To bring freshness to your plants, remember to water them well. There are several solutions for properly irrigating your plants: drip irrigation, micro-sprinkling or even gravity watering. It's up to you to choose what suits you best!

What are the consequences of such a temperature?

Because of the heat, the soil of your plants will dry out and they can very quickly run out of water. If you don't intervene quickly, some of your plants may die.

Excessive heat can disrupt tomato growth and fruit set. Flowers may dry out and fall; this is called blossom drop. Lettuce may bolt more quickly and become bitter in hot conditions. Check ventilation, soil moisture and temperature around the plants.

If you are used to sowing plants all year round, in the event of extreme heat, it is not recommended to sow certain seeds such as lettuce, radishes, turnips, hydrangeas or even hellebores.