An Introduction to Humidity in Your Growing Environment
Welcome to our latest blog… today we will be giving you an introduction to humidty in your growing space, and it’s effect on your environment.
Let us start by explaining what humidity is and how it can affect the growth of your plants.
What is humidity?
Humidity is how we describe how much water vapour is present in the air… and to explain that quite simply, the higher the humidity, the more water vapour is in the air (and the wetter the air will feel).
An environment with a high humidity will have more moisture in the air, whereas an environment with a low humidity the air will be drier and have less moisture. Colder air is usually drier than warmer air, as warm air has a larger capacity to hold on to moisture, which we will explain later.
We always say environment is everything, especially when it comes to growing high yielding plants… and your humidity level is a key factor in your grow room’s environment, so it’s vital to get your humidity levels right!
Humidity plays an important role in photosynthesis and, ultimately, the successful growth and productivity of your plants.
So remember: The more water vapour present in the air, the more humid your grow room will be (and the higher your humidity level will be).
How does humidity affect photosynthesis?
During photosynthesis plants open their pores (stomata) to take in carbon dioxide and then as a by-product they release water vapour back into the air (this process is called transpiration, which we will look at next).
If the air is too dry, the plant will close its stomata to stop it from losing water, however this also stops the plant from taking in the carbon dioxide it needs. At the other end of the spectrum if your humidity levels are too high, the plant’s stomata will not open enough, and your plant won’t get the carbon dioxide it needs for photosynthesis. Plants are very fussy in this sense and your humidity levels need to be just right to ensure the plant will open its stomata to ensure they get the right amount of carbon dioxide for photosynthesis.
How does humidity affect transpiration?
Transpiration will occur more when there is increased movement of air around your plants.
As the relative humidity of the air surrounding your plants increases, the transpiration rate will, in turn, decrease, as water has an easier time evaporating into dryer air than in saturated air.
How do we measure humidity?
Humidity is most commonly measured as relative humidity (RH), which measures the amount of water in the air proportionate to the maximum amount of water vapour the air can hold.
The amount of water vapour the air can hold depends on the temperature.
Humidity can be measured with a tool called a Hygrometer, which measures both temperature and humidity levels.
Generally, flowering and fruiting plants in their growth stage require a humidity of around 70% at a temperature of 26°C.
During the flowering or fruiting stage the humidity should gradually decrease as flowers or fruits develop, down to 50% for the last few weeks.
If your grow room’s RH level falls outside of this region, it could cause a multitude of problems.
Too much humidity can cause issues such as mold and mildew, root rot, pest and disease problems and in worse case plant death.
Too little humidity can cause slow growth, dry leaves, stunted flower and fruit development, leading to poor yields
This can be explained by VPD (Vapour Pressure Deficit), however as this post is an introduction to the importance of humidity levels, we will cover VPD in depth in a future article.
In conclusion
Whether you are growing in a grow room, tent or greenhouse, to ensure success and a high yield, it is essential to monitor and control the humidity levels in your growing space.
So, while we have discussed the topic of humidity above in some detail, the simplest way to control your room’s humidity levels is with a humidifier or dehumidifier, and good ventilation.
If you keep a close eye on and regulate your humidity levels you are on the right track for a bountiful harvest!
GHEDirect LTD, 
