A plant growth apparatus that includes a chamber with multiple layers, a driver and at least one lamp per layer provided in the chamber. The lamp includes a plurality of high intensity red light emitting diodes and a plurality of blue light emitting diodes. The red and blue light emitting diodes are alternately arranged. The driver is capable of individually controlling the intensity of red and blue light, thus, leading to the capability of controlling the light quality. The driver is also capable of controlling the frequency and duty ratio of direct current provided to the red and blue light emitting diodes during the light-period of the photoperiod controlled by the timer.
