One warm white and one cool fluorescent bulb used together will come close to producing the full spectrum of light wavelengths for indoor growing. Special grow lights also produce this quality of light. Incandescent lights produce an adequate quality light, but their heat may damage plant tissues. Quantity Quantity describes intensity or concentration. The quantity of light decreases with distance and angle from the source.
Light quantity is measured in foot candles.
Plants receive maximum quantity of sunlight in summer and minimum in winter because of the angle at which the wavelengths of light hit the plant surface. Plants must be positioned 2 to 6 inches from an artificial light source for the light to be effective. Duration Duration is the time that a plant is exposed to light, critical to growth and flowering. In indoor growing situations, lights must be on for 12 to 16 hours in most instances. Outdoors the duration of light varies with the season.