In this paper, we present development of a control system for achieving energy-efficiency through optimizing light conditions for plant growth in an emulated greenhouse. By taking advantage of daylight harvesting, the system regulates the dimming level of LEDs based on the light irradiance data supplied by red and blue channels which are sensed by light sensors located on the testbed. The system model is obtained and the control system is developed for achieving desired light intensity for red and blue lights at sensor locations when the system is subjected to emulated sunshine. A series of simulations and experiments are presented to verify the control performance.