Certain colors in light rays are important for proper plant growth. Leaves reflect and derive little energy from many of the yellow and green rays of the visible spectrum. Yet the red and blue parts of the light spectrum are the most important energy sources for plants, and plants require more rays from the red range than from the blue. Plants growing outdoors, in greenhouses or close to windows are exposed to a natural balance of the blue and red light rays that plants need. Where plants receive little or no natural light, you must provide additional light from artificial sources.
Most people are familiar with the incandescent light produced by ordinary light bulbs in our homes.
As a single light source for plants, these bulbs are not particularly good. They are a good source of red rays but a poor source of blue. They produce too much heat for most plants and, if used, must be kept away from the plants, thus reducing the intensity of the light the plants receive. They are also about three times less efficient than fluorescent tubes inconverting electrical energy to light. Further more, a standard incandescent bulb's life is often only about 1,000 hours, whereas a fluorescent tube's life is normally 10,000 hours or more.