leaf_cycle=* describes the phenology of 
leaves, for instance evergreen or deciduous.
This key is used as refinement for vegetation, such as woodlands, trees, shrubs or other plants.
Phenology is the study of cyclic and seasonal natural phenomena, especially in relation to climate and plant and animal life.
Common values
Applies to
This tag does not apply on boundary=forest or boundary=forest_compartment entities, only on underlying natural=wood/landuse=forest entities.