Manage humidity
A humidity level suitable for plant growth
Ideally, the humidity level should be between 40 and 80%.
When these conditions are not met, plants adapt how they function, to the detriment of optimal growth.
1. Managing humidity in hot, dry weather
If the humidity level is low, which is the case in hot, dry weather, plants undergo photorespiration.
Plants tend to lose water through the stomata. To limit these losses, the stomata close. Put simply, the stomata are the "entry point" for CO2 used in photosynthesis.
Photosynthesis can therefore no longer take place efficiently, which leads to a loss of yield.
How can you increase the humidity level?
- Ventilate the greenhouse to remove heat
- Put the shade cloth on one side only, preferably the south side
- Install a mister
2. Managing humidity during periods of high humidity
If the humidity level is high (above 80%), mould can develop on the leaves, or parasitic fungi such as powdery mildew or downy mildew can appear.
To limit fungal development, it is necessary to reduce humidity in the greenhouse.
To reduce it:
- Ventilate the greenhouse
- Ventilate the plantings (space the plants sufficiently in the beds or towers, harvest regularly)
- Turn on the ventilation
- Open the shade cloth to let the sun's rays enter easily
When should you turn on the ventilation?The ventilation should be turned on during the transitional seasons, in March/April and from September to November.
In winter, the ventilation brings cold air into the greenhouse, so it is preferable to turn it off.
From May to early September, the doors and vents are open almost permanently. It is therefore unnecessary to turn on the ventilation.