Carbon dioxide, or CO2, is one of the main elements required by plants for photosynthesis. But plants in greenhouses can quickly run out of CO2 if outside air is not allowed in. So when the winter sun shines and plants become active, they may not grow at all.
Ben Geijtenbeek, Senior Crop Technical Specialist at Syngenta Flowers, based at Enkhuizen in the Netherlands, describes a lack of CO2 as “the hidden enemy”.
He says, “In general, there is sufficient CO2 in the air. But in winter, because of the temperature, sometimes greenhouses are kept closed. The CO2 is used up and the assimilation process, or photosynthesis, is delayed or blocked completely because there is no exchange with the outdoor air to reload the greenhouse with CO2.”
Ben says this can become worse on sunny days when greenhouse plants become more active and require more CO2.
“Because we cannot see or smell a shortage of CO2, it is a hidden enemy, which can easily block growth. A chain is only as strong as its weakest link.”
To avoid a lack of CO2, his advice is to always ensure the greenhouse is ventilated to reload it with this important element, especially on warm and sunny days.
“The windows need to be opened a few centimetres regularly or, when it is freezing outside, maybe the door can be opened a little, at least a few times a day for half an hour.”
This simple tip will prevent growth from being blocked and help maintain plant quality even in less favourable conditions.
Syngenta Flowers