Lighting system for a greenhouse

A method of illumination comprising:

• providing a greenhouse;
• providing for the greenhouse an exterior wall structure having an end wall and two side walls at right angles to the end wall, each of which includes primarily transparent panels allowing entry to an interior of natural light;
• providing in the greenhouse a plurality of elongate parallel benches located side by side within the interior at right angles to the end wall and arranged to provide generally horizontal support surfaces for supporting plant materials thereon for receiving the natural light and growing within the interior;
• and providing a pattern of artificial light to the plant materials on the support surfaces by:
• providing a plurality of lighting fixtures;
• mounting the lighting fixtures on a plurality of rails arranged in parallel spaced positions in a common horizontal plane at a height above the benches with the rails of the plurality of rails extending parallel to the benches;
• providing at least one intermediate rail of the plurality of rails and a first and a second side rails of the plurality of rails where the first side rail is located adjacent the first side wall and the second side rail is located adjacent the second side rail;
• mounting the lighting fixtures such that each rail supports a plurality of the plurality of lighting fixtures in a row along the rail;
• providing for each of the plurality of lighting fixtures a generally parabolic reflector facing generally downwardly toward the plant material for directing light toward the plant material;
• providing for each of the plurality of lighting fixtures a cross-section of the generally parabolic reflector which is substantially constant along a parabolic axis thereof;
• providing for each of the plurality of lighting fixtures a lighting bulb at a position within the generally parabolic reflector such that light therefrom is reflected by the generally parabolic reflector;
• providing for the parabolic reflector a center line of the parabolic reflector generally parallel to and spaced from the parabolic axis thereof so as to define a lighting direction of light from the bulb reflected by the parabolic reflector;
• providing a fixed pattern of illumination from the lighting fixtures mounted on said at least one intermediate rail by locating the lighting fixtures thereof in fixed position thereon such that the center line of the parabolic reflector is directly above the parabolic axis so that the lighting direction is maintained at a fixed direction angled vertically downwardly;
• providing a fixed pattern of illumination from the lighting fixtures mounted on said first side rail by locating the lighting fixtures thereof in fixed position thereon such that the center line of the parabolic reflector is located upwardly and outwardly of the parabolic axis toward the first side wall so that the lighting direction is maintained at a fixed direction angled downwardly and inwardly away from the first side wall;
• and providing a fixed pattern of illumination from the lighting fixtures mounted on said second side rail by locating the lighting fixtures thereof in fixed position thereon such that the center line of the parabolic reflector is located upwardly and outwardly of the parabolic axis toward the second side wall so that the lighting direction is maintained at a fixed direction angled downwardly and inwardly away from the second side.