Light for Indoor Plants
All plants need light; even those that tolerate low light conditions require some sort of illumination for part of the day. Light can come through windows as natural light, and from overhead lights and desk lamps as artificial light.
Natural light is usually brighter than artificial light. It is important to note the direction of the window when placing plants. Putting a low light plant in a south or west-facing window could easily roast the plant. Also, putting a high light plant in a north facing window could result in a spindly weak specimen.
Artificial light is the most common form of illumination in offices and atriums. The light can be in the form of incandescent, fluorescent, high pressure sodium, metal halide and halogen.
The Visible Light Spectrum
The visible light spectrum contains all the colors emitted by a light source when shined through a prism. Not all colors are visible to the naked eye (such as, ultraviolet light and X-rays). The red and blue parts of the light spectrum are the most important energy sources for plants. Plants require more rays from the red-orange range than from the blue range. Leaves reflect and take little energy from many of the yellow and green rays of the visible light spectrum.