Abstract: A rotating lamp fixture includes a plurality of lamps, attached to an arm which extends outwardly from a housing preferably mounted to the ceiling of a building. The arm is connected through a torque coupling and a gear train to the shaft of an electrical motor. The motor imparts a relatively slow circular or orbital motion to the lamps through the arm for serving as an artificial light source. The provision of a rotating light source reduces by at least one-third the number of fixed light sources needed for effectively controlling the growth of vegetation. The rotating lamp fixture increases the growth rate, improves the uniformity of growth, and/or precisely controls one or more other growth characteristics of the vegetation. Other features are also disclosed.