Many plants are highly responsive to the changing balance of light and darkness each day, which is known as the "photoperiod."
Outdoors, the reduction of daylight hours signals the coming end of the growing season, triggering annual plants to complete their life cycles by flowering and/or producing seeds.
Indoor growers who want their crops to produce flowers or fruit need to manage the length of time when lights are on and off so that the photoperiod mimics those outside conditions.
