Ventilation

From BonsaiWIKI

ventilation is the free movement of air around a bonsai. Ventilation is required to ensure that trees can carry out photosynthesis properly. If light and air can't penetrate to the inner branches, they are in danger of dying back or harboring disease and insects.

Ventilation can be improved by thinning the foliage of the bonsai and by exposing it to wind.