A lamp apparatus for horticulture lighting is disclosed. The lamp apparatus is a high intensity electrodeless plasma lamp with an optimized spectrum for horticulture applications. The spectrum is provided from single light source and consists of peaks in the blue range of the spectrum, 400 nm to 470 nm, needed for early growth cycle of the plant as well as peaks in the red range of the spectrum, 600 nm to 700 nm, desirable for flowering cycle while providing lower amount of light in the green spectral region which is typically reflected by the plants. The ratio of the red spectrum to blue spectrum provided by the lamp can be varied by adjusting the RF power to the lamp.
