The temperature in your grow room is very important for the photosynthesis of your marijuana plants. For example, low temperatures reduces evaporation through the leaves. The result is that the suction force, which takes up nutrients via the roots, becomes smaller. The nutrients that are necessary, but aren’t absorbed, remain in the growing medium and eventually disintegrates in the root environment. A high acidity in the growing medium reduces the working of the roots which makes the plant absorbs less water and nutrients, and the growth can even come to a halt. So what posed as a small external imperfection at first, can have serious consequences in an entirely different part of the plant. Therefore it’s very important to create a good climate in your grow room.
The temperature in your grow room depends on several factors. The location of your room in the building is an important one; in a basement it’s a lot cooler than in an attic with a flat roof. Aside from that, the size of your room, the airflow, the number of lights and the extraction rates play an important role. Keep this in mind when building your grow room. When the light is turned on, an ideal temperature for the cuttings and seedlings is between 68ºF and 77ºF (20ºC and 25ºC). As the plants get older they can evaporate a little bit more and the temperature may increase to a maximum of 82ºF (28ºC). When the lights are off, the temperature should lie between 62ºF and 72ºF (17ºC and 22ºC). Another important rule is that the temperature differences between day and night cannot be too high, a maximum difference of 10ºC. So when it’s 82ºF (28ºC) during the day, it cannot go below 64ºF (18ºF) at night. A temperature difference of 5ºC is ideal.