Cultivation Dehumidification

by | May 29, 2019

Written by Editorial Team

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In areas with less than desirable outdoor conditions, indoor cannabis grow houses are ideal. Growers gain control of the humidity levels, temperature, and lighting and can alter them to the precise needs of the plants to produce the healthiest growth possible, but creating these optimal environmental conditions is quite the balancing act.

Too much water vapor in the air diminishes the health of the plants and increases the likelihood of developing humidity-related diseases. Indoor grow facilities should always be equipped with a large-scale, potentially customized dehumidification system to avoid these adverse outcomes.

Indoor grow houses measure water vapor in the air using relative humidity

There are three types of humidity: specific humidity, absolute humidity, and relative humidity. When measuring the amount of water vapor in the air, cannabis growers use relative humidity (RH). The percentage given expresses the ratio of how much water the air can hold at a given temperature. For example, two rooms can have the same moisture levels, but in one where the temperature is warmer, the RH will be lower because warm air can hold more water molecules. In a colder room, the RH would be higher since it needs more water to reach its max humidity level.

What affects humidity control?

Along with temperature, the region where cannabis grows, its genetics, and the stage of growth all affect relative humidity levels.

Colder climates don’t see as much moisture in the air compared to tropical climates, like Florida. However, colder regions must then control humidity levels far more than warmer regions. Certain cultivars are also bred to withstand and better acclimate to higher humidity levels, just as there are cultivars that thrive in less humid areas.

As mentioned before, cannabis plants need humidity for their development. The trick is keeping the grow rooms at the correct RH throughout each growth stage.

When are dehumidifiers important for cannabis cultivation?

Dehumidifiers extract moisture out of the air, so the RH reaches the required percentage. Determining the dehumidifier’s ‘size’ depends on the total pounds of water it can remove per hour. The appropriate size a grow house needs is determined by many factors including, but not limited to:

●      How much moisture builds up in the grow room

●      The methods used to water the plants

●      The number of windows and doors

●      Operating the dehumidifier alongside an existing HVAC system

Dehumidification is the best preventative measure against mold growth, fungi, and powdery mildew. The worst and most common mold is Botrytis, aka ‘bud rot.’ This kind of mold growth can damage entire cannabis crops, so monitoring humidity levels throughout the plant’s growing cycle is crucial, especially at the flowering stage. Any plants with bud rot should be immediately removed to keep them from afflicting the other plants.

Too little or too much humidity can also create nutrient problems. Humidity affects the water loss and absorption rates in cannabis plants. The correct botanical term for this process is called transpiration. Transpiration, by its definition, is partly responsible then for the plant’s nutrient intake levels. If the humidity is too high, the plants will absorb less water, thereby limiting the nutrients it receives.

Why is humidity important for cannabis plants?

Cannabis plants can’t grow effectively without some humidity. The key is maintaining the percentage of water vapor in the air based on where the crop is in the growing phase. Growers need to modify both the humidity and temperature levels if they hope to harvest high-quality flower riddled with trichomes.

Here’s what most growers agree are the optimal humidity levels for the four different grow stages:

●      Seedling– Seedlings need high humidity, at least 70%, so their root systems can develop.

●      Vegetation– Since vegetative plants have stronger root systems, they can withstand moderate humidity levels falling between 40-60%. Many growers like to reduce the humidity by 5% every week leading up to the flowering stage.

●      Flowering– Controlling the humidity in the flowering stage is one of the most essential parts of the cultivation process. This is when bud rot is most likely to form if the relative humidity is too high. Some growers lower it below 40% to try and have the plant produce more resin, but a range of 40-50% is ideal.

●      Later flowering– By the time the plants are ready for harvest, humidity should be between 30-40%.

Cannabis cultivation is a combination of skill and technology

In order to obtain a high yield of top-quality cannabis, growers must consider the best environmental conditions for every grow phase. This knowledge is what separates the average cannabis cultivator from the masters. New cultivation technologies make it easier to control cannabis cultivation from seed to sale. Combine these various gadgets with a grower’s skills, and the quality of the cannabis flower will be taken to new heights.