The invention is directed to providing artificial light optimally to plants during its growth cycle in a greenhouse (350) or growth chamber. This is achieved effectively by moving both the lighting device (2, 3 and 4) and its emission pattern to maximise incident light on the plants (5, 6 and 7) being cultivated.A horticultural lighting device of the invention illuminates plants so that said lighting device (2, 3 and 4) is moved vertically and at least one light emitter (3 and 4) and/or reflector (2) is rotated to maximize light exposure from said lighting device on said plants (5, 6 and 7). In the best mode the movable and rotatable lighting device is used to grow very high plants. The lighting device (2, 3 and 4) is moved by a motor programmed to change the position of the lighting device and the orientation of the emission pattern in accordance with the growth cycle of the plants in the greenhouse (350) to maximise incident flux on said plants (5, 6 and 7).
