Ventilation is one of other important factors in growing, and the more plants, there are in the growing area, the more important ventilation becomes. The reason ventilation is so important is that marijuana plants breathe through their leaves and also emit any toxins through their leaves. If the ventilation is poor the leaves of the ganja plant can become clogged and unable to breathe or emit the toxins and this will cause the leaves to die.

The amount of ventilation needed will depend on the amount of plants, with just a few plants in a closet growing area opening and closing the door is often enough ventilation for the plants when tending to them. When growing in other secret areas of the house like the basement or attic, the use of a fan will create the ventilation needed and it will also stimulate the plants to grow. These plants are healthy not only due to the ventilation.  The air from the fan also helps to promote the plants to grow sturdy stems and because the plants do not have to deal with weather issues like wind and rain they concentrate on producing leaves and resin.