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.

It is important to choose the location of your greenhouse carefully. Indeed, if you place your greenhouse in a shadier area, the heat will not rise as quickly as if it is in full sun in your garden. Moreover, in addition to the heat problem, the sun's rays can be harmful to certain plants which will have burnt foliage. So to shade your greenhouse, if you have already placed it in full sun, there is the solution of investing in a shade cloth or a shade net which is placed directly on the greenhouse. It can lower the temperature by up to 10°C in your structure. If you are planning to buy a greenhouse and do not want to buy a shade net, then you can also invest in a structure that has opaque walls.

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.

If we take the example of tomatoes, in the case of too much heat, they stop developing. And if they experience too much variation in temperature, the flowers dry and fall: this is called flower melting. In the case of salads, stress due to high heat will encourage the plant to set more seeds and its leaves will no longer be edible.

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.