A lighting device suitable for promoting plant growth, said lighting device comprising: —(i) a first group of LEDs comprising a plurality of LEDs adapted to generate a first emission spectrum having a peak between 450-460 nm (royal blue light)； (ii) a second group of LEDs comprising a plurality of LEDs adapted to generate a second emission spectrum having a peak between 630-670 nm (crimson light)； (iii) a third group of LEDs comprising a plurality of LEDs adapted to generate a third emission spectrum having a peak between 720-740 nm (cherry red light)； (iv) a fourth group of LEDs comprising a plurality of LEDs adapted to generate white light； wherein the intensity of the light output generated by each group of LEDs is adjustable independently of the other groups.
