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Controlling Humidity With A Dehumidifier

Learning to control humidity can be the key to your gardening success; here we explore the role dehumidifiers play in producing the best outcome for your harvest.

Controlling Humidity With A Dehumidifier

Learning to control humidity can be the key to your gardening success; here we explore the role dehumidifiers play in producing the best outcome for your harvest.


transpiration Click to enlarge.

Growing in a sealed or semi-sealed environment, like a grow tent or green house of any size can present the grower with a constant issue—humidity. Even set-ups in the driest of climates can fall victim to erratic levels of atmospheric moisture. Although often overlooked in the growing process, having the proper knowledge to manipulate the balance of humidity in your grow environment can impact the size, quality, and potency of your harvest. Most of us know that our plants must take in water to survive, however many are unaware that plants release up to 97% of that water back into their environment through transpiration. For set-ups with multiple plants, the accumulation of moisture let off can cause humidity and heat levels to spike out of control. This build up of humidity can wreak havoc on your harvests, and without your constant attentiveness or the help of a dehumidifier, the health of your herbs can tarnish in a matter of hours.


Click to enlarge. Click to enlarge.

Humidity, Rot, and Mold

The needs of our plants change over time; as such, the methods used to maintain healthy plants must also be adapted to their various stages of development. In order to maintain optimal health of your plants it is ideal to keep younger plants, seedlings and early cuttings, at a higher humidity. Keeping your set-up at an relative humidity (RH) up to 70 or 80% will allow for roots to properly develop and optimal nutrients to be absorbed. Once your plant has begun to root and is well established however, the humidity needs to be decreased. The vegetative stage should be about 40 to 70% RH, flowering and blooming stage is optimally around 40 - 50% RH. Because spores and mold tend to thrive during the flowering period, it is important to have a plan for lowering the humidity of your set-up during this time. Prior to being harvested, plants should be kept at 40% RH or lower. It is important to promote air movement both under and over the leaves of your plants. The image to the left shows mildew buildup on a leaf.




The Role of Dehumidifiers

While methods of raising the humidity of your set-up are quite simple and common, many find the process of lowering their humidity to be much more difficult. For growers looking to take a stronger hold of their plant’s environment, dehumidifiers offer the simplest solution for lowering humidity without the risk of over cooling the atmosphere or stressing your herbs. Dehumidifiers work by processing the moist air produced by your plants. After humid air is pulled in, coils inside of the unit remove excess moisture before dry air is filtered back into your grow environment. This process prevents the air in your set up from getting too moist, protecting your harvest from hazardous mildew and rot.



Dehumidifiers are also a great option for those looking to reduce their carbon footprint and make their set up more self-sustainable. The dehumidifiers offered by Quest and Sunlight Supply are especially suited for this. After the moisture is removed from the air, a reservoir inside the unit collects the accumulated water. The water produced is both low in pH and total dissolved solids (TDS) making it the perfect way to hydrate your plants. This presents growers with the opportunity to increase the control they have over their set-up by using the moisture naturally produced by their plants to produce clean, fresh water.


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Another common method for removing excess moisture from a grow environment is to use an air conditioner. As air cools, it can't support as much water vapor which leads to condensation on interior walls and surfaces. While this method can work to some degree, the drawbacks can be just as damaging as high humidity. Although air conditioners can aid in removing moisture from the air, they also make the environment significantly cooler. Exposure to this combination of cold moisture can cause stress and leave your plants vulnerable to disease. Instead of protecting your plants, you can actually speed up the deterioration of your harvest by creating an environment that is more suited for the development of mold rather than growing plants.

The key to harvesting the highest quality plants is finding the proper RH balance. It is best to keep your grow at a higher RH until your plants have reached the flowering stage. Once in the flowering stage, it is important to provide your plants with a low humidity to ensure they remain healthy until they are ready to be enjoyed. Use of a dehumidifier can ensure that you are in constant control of the overall health of your grow. The best solution is to pair your dehumidifier with an environmental controller that can monitor humidity levels and turn on the dehumidifier when its needed.


Questions? Call 888-815-9763 or email [email protected].