The Power of Humidity

Water is one of the most abundant molecules on the planet and its power cannot be underestimated.

Humidity is the amount of water vapour that is present in the air. Excessive humidity can promote the growth of mould and bacteria and can encourage the presence of pests. Dehumidifiers and humidifiers help you to control the water vapour levels.

Humidity is typically measured as Relative Humidity and abbreviated to RH and It is the percentage of the maximum amount of water vapour that the air can hold at a specific temperature.

There is a direct relationship between temperature and humidity and the warmer the air is the more water it can hold. 

A big myth is that plants do not enjoy high humidity levels but in actual fact they do. Playing it safe is a natural reaction to this but careful management of humidity can avoid the bacterial and fungal problems that are often associated with it.

The Science

The water transportation within your plants determines how well they absorb nutrients and stay hydrated. Plants give off water vapour through their leaves and this is part of the transportation process. The humidity of your grow room will affect this.

There is a process known as Osmosis. This is when water moves from areas of high humidity to areas of low humidity. The bigger the difference in humidity levels the faster the water will move. Humidity within plants is actually close to 100% which is of course the highest possible. 

Targeting Humidity

If the air is warm then you need a higher RH. It is easier to manage this at lower temperatures because you don't need to humidify quite as much and will need to extract less out it the environment.

Cuttings and Seedlings

When plants are young then a high humidity is ideal. Because they do not yet have roots they cannot lose too much water. Depending on the temperature a RH of 70-80% is ideal. This means that they can focus on growing their roots rather than correcting their own humidity.

Veg Growth

A lower level of humidity is required at this stage and between 50-80%, again depending on temperature, is the level you should aim for. Plants begin to draw water through their roots to replace that lost through the leaves. Because the leaves grow rapidly there is less stress on each leaf so a lower humidity is fine.

However, if the humidity becomes too low the plants will draw more water through the roots and therefore may take in too much fertiliser.

Flowering

Buds will start to form at this stage so to reduce the risk of rotting it is good to lower the humidity. Between 40-60% is good for this period of time.

Products that can help to control the humidity in your grow room include the RAM 12 Litre Dehumidifier, the Sonic Air Humidifier and the RAM Ultrasonic Humidifier