Humidity refers to the amount of water vapour in the air in a room or certain space at a particular time. Marijuana leaves develop narrower in a humid environment, mostly caused by excess dry heat because the excess water they give out through the leaves is not able to evaporate properly. A grow room needs to be dry to allow the leaves to ‘breathe properly’. This mostly occurs when the room in which the plants are growing in is not properly ventilated such that none of the hot air ...