Growing saintpaulia under fluorescent lights

By James D. Rubottom


Light is something that we often take for granted. What is this thing that we call light? Essentially, light is a form of energy. The energy in light is responsible for much of what we have on the planet. Light energy consists of waves. In some ways you can think of it as being like sound waves. In this respect, light has different frequencies, just like sound. This means that light can take on a number of different forms based on the frequency of its waves. The wavelength determines the type of light and how the human eye perceives it.

Photosynthesis is the biological process by which the energy of sunlight is absorbed and used to power the formation of organic compounds from carbon dioxide and water. This process ultimately supplies the energy required by plants for their continued survival. This photosynthetic process can be divided into two stages:

Because African violets require relatively low light levels to grow and flower, fluorescent lighting has been adapted by many growers. This type of lighting was first exhibited at the Chicago Centennial Exposition in 1933. Fluorescent lamps emit more light per watt than incandescent bulbs. Their light is generally whiter, but if the chemicals in the lamp's interior phosphor coating are changed, different types of light--such as the "plant light" that mimics sunlight--can be produced. Today fluorescent tubes probably provide the best artificial light sources available for growing African violets and other gesneriads in the home.

Advantages of using fluorescent lights include:

In spite of the above advantages there are some disadvantages in using fluorescent tubes:

Tubes listed as white or daylight are less desirable because they produce less red and blue light. Cool white tubes produce some red rays in addition to orange, yellow-green and blue rays. You can even supplement cool white tubes with incandescent bulbs to boost red rays. The special tubes mentioned earlier have been developed for growing plants. These have a higher output in the red range to balance the blue output. You can use one plant-growth tube (such as GroLux Wide Spectrum) to each cool white tube or you can use cool white and warm white in combination.

As a general rule, you should have your fluorescent lights on from 12-14 hours each day. The distance of each tube above the foliage of each plant should be about 8 to 10 inches. If your tubes must be slightly higher then you might want to consider slightly lengthening the period that your lights are on. Also be certain that you space your plants in such a way as to allow light between each plant. Take care that one plant is not shading another on the shelf.

Fluorescent tubes are long-lasting, but that doesn't mean that they last forever. The tubes produce less light as they age. This means that you need to replace the tubes approximately every six to nine months. As the tubes age they develop dark rings at each end. Because replacing tubes with a new tube will cause an increase in light level you can alternate swapping out tubes in fixtures designed for two tubes. How can you keep track of when to swap out your tubes? Many tubes actually have a location near the end of the tube where you can write the month and year with a marking pen.

I hope that this introduction to fluorescent lighting will be helpful. Remember that everyone's growing condition vary so what I have tried to present is only a set of general guidelines for growing under fluorescent tubes.


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