Fluorescent lights come in different types and strengths, and not all are equal as far as plants are concerned. Plant requirements vary as well, and a light that is suitable for growing mint or creeping Charlie will not necessarily work for begonias or tomatoes. Using the wrong light, fluorescent or otherwise, can cause the plant to develop significant growth problems, fail to bloom or even die. Learning a few basics about light and plants will help you determine if fluorescent light will help specific plants to grow.
Sunlight contains many different kinds of light that are visible when the light is directed through a prism. These colors, also seen when sunlight filters through water droplets to form a rainbow, range from red at one end of the spectrum to blue at the other. Although there are other colors in between -- such as yellow, violet and orange -- growing plants mainly require red and blue light waves. They also must have light that is bright enough to allow them to photosynthesize their food, and the light must be available for enough hours each day that the plant can produce adequate food for survival and growth.
Foliage plants, those without flowers or fruit, need only blue light waves to grow well. Because blue light supports photosynthesis and leaf growth, most plants will be able to live and grow with this type of light alone. The disadvantage of such a limited light source, however, is that although flowering plants will grow under blue light waves, they will never produce any flowers. To be able to flower, plants must also have red light waves.
Fluorescent lights provide almost all blue light waves. This makes them excellent for growing foliage plants. Use them to start seedlings as well. Fluorescent lights are cool, making them safe around plants, because they won’t burn the leaves. Since standard fluorescent lights tend to be limited in intensity, place them very close to growing plants, about 2 inches for seedlings and 4 inches for older plants. Leave the lights on about 14 to 16 hours per day for best results.
Specialized fluorescent lights designed specifically for growing plants, often called grow lights, are readily available from virtually any source that sells indoor gardening supplies. The exact specifications of the lights vary by manufacturer, but all include red light waves and are suitable for growing flowering plants as well as foliage plants. Use these for indoor plants that receive little or no sunlight. Most will also help plants such as tomatoes and peppers to produce and set fruit, but check the light before purchasing it, as some may not be adequate for fruits and vegetables.