For those interested in learning more about the science behind this, there is a term used by greenhouse growers known at VPD, or Vapour Pressure Deficit, that roughly measures the temperature and relative humidity.
This humidifier is an evaporative swamp cooler that holds 7 gallons of water at a time – great for hot, dry climates.
I like the Ambient Weather WS-07 Wireless Thermo-Hygrometer because it lets you remotely check the temperature and humidity from another room (don’t forget to get 6 AAA batteries).
40-60% RH (if you see wet spots forming on the leaves, humidity is too high or you need to increase air circulation). Beware of white powdery mold in humid grow spaces!
Install TeamViewer (it’s free for personal use) or you can also use Windows Remote Assistance (not as user friendly in the beginning, but a good choice).
Two scenarios can occur:
If the lights of your grow tent are always on, the temperature of the contained air is raised and hence the relative humidity. Poorly lit grow rooms have cold and dry air (low humidity).
Why Is Humidity Important For Cannabis Plants?
When the air is dry (low relative humidity)
The high water gradient created between the plant and the surrounding air causes high water loss. The marijuana plant will try to prevent this by closing the stomata, a process that compromises the vital respiration process.
Did you know that mold infestation on one cannabis flower can ruin your entire harvest? Lowering the humidity in this stage is, therefore very crucial and should not be overlooked. The humidity can also be reduced below 40% when the cannabis is close to harvest. This, however, depends on how your cannabis plants respond to changes in humidity.