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. Fluorescent tubes provide the best artificial light sources available for plants in the home. Other light source such as sodium lamps may be used but are not normally available or adaptable for home use.
Many indoor gardeners use cool white fluorescent tubes.
Warm white fluorescent tubes also seem fairly effective, but fluorescent tubes listed as white or daylight are less desirable for indoor plant growth. Cool white tubes produce a small amount of red rays in addition to orange, yellow-green and blue rays. However, the red light produced usually is not enough for many plants unless windows or other artificial lights produce additional red rays. A few incandescent bulbs in the growing area can furnish needed red rays. A general ratio of incandescent to fluorescent light is about 3 to 10, so for every 100 watts of fluorescent light, you should provide about 30 watts of incandescent light for a better red to blue light balance.