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Humidity is the measure of the volume of water in the air at a given temperature. Higher humidity (>75%) can lead to slowed growth due to reduced evapotranspiration and can increase the potential for disease that favors high moisture, such as powdery mildew. A circulation fan in the growing room and frequent air exchanges can reduce the amount of humidity in the air which will maintain an ideal environment for plant growth. Low levels of humidity (<20%) can also reduce growth by reducing the amount of moisture around the leaves of the plant which creates a situation of water stress in the plant. Using evaporative cooling or adding a humidifier to your growing environment can increase the level of humidity in the air and maximize the plant’s osmotic potential.

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