Cannabis Nutrient Deficiencies? Pests? Diseases?

by Kenny | Aug 22, 2024

Humidity and Cannabis; What Are The Best Humidity Levels For Growing Cannabis

-Humidity & Cannabis-

    Humidity is one of the key factors in producing a plentiful, potent, and healthy cannabis flower. Sometimes this is overlooked or is a secondary concern for growers because they don’t understand that humidity levels can impact the quality and volume of their final product. From seedling through its entire life, including processing and packaging, cannabis moisture needs to be well regulated to produce something worth the effort.

    Moisture levels in a cannabis facility are typically measured in two metrics; relative humidity (RH) or vapor pressure deficit (VPD). RH is a measure of the saturation of moisture in the air. A high percentage indicates the air is close to being so saturated that water will begin to condensate like dew on the morning grass. VPD, on the other hand, is a measure of the difference in vapor pressure (a measurement of the point where vapor becomes liquid) from inside the plant to its surroundings. This can be determined by using the temperature of the room and the RH in the room. There is an ideal balance for your plants; however, it usually takes a few rounds to determine that excellent range.

     Failing to monitor these measures of moisture can affect your plants and your final product. During the early stages of growth, it can cause plant stunting. If the moisture is off during flowering, it can stunt your flower development and/or produce white powdery mildew. During late flowering, it can cause bud rot. During dry / cure, it could ruin terpenes or mold the buds. The most nightmare-inducing thought is that after it’s been packaged, cannabis could become moldy and unusable. Regulating moisture is so important for plants that it is unthinkable to ignore it during any part of the growing process. To help you avoid these possible disasters, we have provided some insight on how to keep moisture well regulated.

-Equipment & Best Practices-

Cannabis Humidity Levels for Growing:
There are optimal levels of humidity for each stage of your cannabis plant. In the early stages of life, a cannabis plant generally needs more humidity than in the later stages. This is something to take into account as you grow your weed plants from clone to finished product.

Best Humidity for Growing Cannabis (Relative Humidity)  

Seedlings - 60% - 80%
Vegetation - 55% - 70%
Flowering - 40% - 50%
 
Understand that the ideal humidity levels are just a guide, and it is what we use to grow. By no means are we suggesting that these are the only levels to use, do your research and find out what works for your cannabis plants!
 
Invest in quality humidifiers/dehumidifiers:
 The easiest way to add or subtract humidity in your grow room is by using humidifiers and dehumidifiers. It can be a pain trying to manually mist a room or mess around with low-quality equipment that is hard to clean and maintain, which in turn could lead to the spread of bacteria. Make sure that your humidifier/dehumidifier is rated for a grow room/tent around the same size as yours. This will help keep power bills down and humidity levels consistent. Dehumidifiers are relatively simple compared to humidifiers; however, you may want one with a large reservoir or one that you can run off into a drain requiring you to empty the water less frequently. 
 
Create a culture of consistent monitoring:
 Making sure to constantly be checking humidity levels can prevent issues from developing during the growing operation and makes it easier to pinpoint the origins of a problem if one should occur. Measuring temperature and RH is crucial because it can cause major issues for the next stage of the plant's life if this is off. On top of monitoring, make sure to keep a record of conditions and changes made. 
 
Clean your equipment:
 Cleaning your humidifiers and dehumidifiers is important since they are cycling so much air, which can cause bacteria to spread. If bacteria or mold were to develop in the water reservoir and happen to be picked up and passed through the fan, then your entire crop is at an increased risk of getting sick. 
 
Humidifier automation:
 Automating humidity controllers can be achieved to lessen the workload and ensure proper humidity levels at all times. Too high, you run the risk of a calcium deficiency and mold developing; too low, and the plant is at risk of stunting. Having an automated humidifier system in place that can be set to a specific RH is great so that it doesn’t need 24/7 monitoring from workers. We will explain how to create your own automated humidity system in a later blog, but for now, just understand it is something that takes a little extra work but might be worth it for your grow room!
 
https://www.royalqueenseeds.com/blog-indoor-cannabis-growing-relative-humidity-and-temperatures-n243
 
https://www.cannaconnection.com/blog/18563-ideal-humidity-levels-for-growing
 
https://www.cannabisbusinesstimes.com/article/moisture-matters/
 
https://cannabisindustryjournal.com/feature_article/moisture-matters-why-humidity-can-make-or-break-a-cannabis-cultivators-bottom-line/