The present invention discloses a system for illuminating plants in an indoor site, comprising a plurality of illumination units for emitting light in intermittent pulses； a central unit connected to the plurality of illumination units for synchronizing the operation of the plurality of illumination units, such that two or more plants clusters receive light in intermittent pulses emitted in the same time. The illumination units may contain wireless communication units and are synchronized wirelessly. The present invention also discloses adjusting an illumination plan of plants according to information of various types from a central server and adjusting the height of the illumination units accordingly. The system adjusts illumination plans according to information received from one or more sites, and predicts problematic situations from a series of images.
