The present invention is directed to a passive solar greenhouse for controlling the greenhouse's interior environment and maximizing photosynthetic metabolism within the plants grown therein through regulation of sunlight, temperature, humidity, and carbon dioxide levels and methods optimizing plant growth conditions by using passive solar greenhouse of the present invention. Generally the greenhouse has a sloped glazed face which faces substantially true south in the Northern hemisphere and substantially true north in the Southern hemisphere with a predetermined slope angle designed to maximize incident solar radiation (insolation) and increase the interior temperature during the colder months of the year while reducing overheating during the warmer months of the year.
