Many growers ask themselves: What is the best grow temperature during the day and night?
The growing temperature is a very important determining factor. If the growth temperature is not right, the plant will grow less or not at all.
Science has found that the best temperature around the leaf for any crop plant is 24 °C, ensuring maximum growth and flowering both day and night.
During the day, the plant produces energy for growth (assimilation), and at night the plant consumes energy for growth (respiration).
The art of cultivation is to ensure that the plant produces as much energy as possible during the day and consumes as little as possible at night.
We can stimulate this during the day by adding a little more CO₂ and lumens (light) and by stimulating evaporation under the leaves (in adult plants) through air circulation. Of course, be careful of excessive evaporation.
The greatest growth occurs where the gap between assimilation and respiration is the largest.
If, however, the daytime temperature is 3 °C higher than the optimum (27 °C), the difference can be balanced by lowering the night temperature by 3 °C to 21 °C, still achieving the same optimal growth.
However, the temperature should never drop below 20 °C day or night, because at temperatures below 20 °C, a phosphorus deficiency occurs.
The colder the temperature drops below 20 °C, the more difficult the phosphorus transport becomes. This also applies to soil temperature.
If the temperature becomes too high, plants start to transpire more in order to maintain a workable temperature. The plant will then need more water.
In hydroponics, it is often observed that the plant has enough water, but in high heat produces large, fluffy flowers.
This happens when the nutrient value (EC) in the water is too high. The plant must release its heat and therefore creates a looser surface near the flowers to give off heat.
This can easily be solved by lowering the EC in the water.