Houseplants add warmth and interest to indoor rooms. Artificial lighting with fluorescent lights is the most cost-effective way to provide extra light for plants that do not get enough sun. Plants that receive no sunlight need intense artificial light for 12 to 18 hours a day. Plants need certain wavelengths of light for best growth. The red and blue parts of the light spectrum are the most important in plant photosynthesis. Red light is necessary for flowering and fruiting, while blue light encourages foliage growth.
Cool-white Fluorescent Tubes
Cool-white tubes are the most common fluorescent lights used for plant growth. They produce a small amount of the red wavelength and more of the blue. Cool-white lights are good for starting seeds and for leafy plants where flowering is not desired. Cool-white tubes provide plenty of blue rays, but not enough red light to support plant flowering and fruiting.
Warm-white Fluorescent Tubes
Warm-white tubes provide primarily the red wavelength and less blue light. They do not produce enough blue light to encourage the growth of foliage and stimulate photosynthesis. Warm-white bulbs are often used to supplement cool-white tubes.
Combining Fluorescent Tubes
A combination of warm-white and cool-white tubes provides a good balance of red and blue wavelengths needed by plants. Install the tubes side-by-side in the same fluorescent light fixture. Another good combination is adding a warm-white tube to a full-spectrum bulb or grow light.
Grow lights are special fluorescent tubes for growing plants. Traditional grow lights produce a balance of red and blue light to provide the wavelengths needed by plants. Newer full-spectrum grow lights mimic the wavelengths provided by natural sunlight. Full-spectrum lights look natural when illuminating plants because they provide light in the green and yellow wavelengths, which plants reflect. Grow lights are more expensive than other fluorescent tubes and most have a shorter lifespan.
Compact Fluorescent Lights
Compact fluorescent lights, CFLs, are available in full-spectrum bulbs that deliver all colors of light and cool-spectrum bulbs that produce mostly blue light. These lights are more intense than regular fluorescent tubes, a distinct advantage for the plant. Place them in a regular incandescent fixture such as a shop light for spot lighting. They burn much cooler than incandescent lights and can be placed close to the plant.