A greenhouse has an exterior curtain wall structure formed by spaced tubular posts carrying external transparent panels and bottom non-transparent wall panels below a sill with the panels spanning the posts. A plurality of benches is located within the interior at spaced positions along one side wall with the width of the benches being equal to the post spacing to form a modular construction. A lighting system is matched with the modular construction of the exterior and includes rails aligned with the posts which carry a row of lighting fixtures arranged for common height adjustment to an optimized predetermined height. The lighting fixture includes a parabolic reflector adjustable to incline the directed light inwardly from the side wall and to change the location of the bulb axis relative to the parabolic axis. The ballasts for the lighting fixtures are housed outside the main greenhouse area in a common cabinet forming a panel in the wall structure.