My experience with growing seedling plants under lights is that no special type of Fluorescent is necessary. This may sound like an unwarranted challenge to the claims of manufacturers who advertise that their product gives more efficient light, or is indeed an indispensable adjunct for the growth of plants. Yet, let us look at the evidence before pronouncing judgement.

In my basement, I have a framework which supports plants in containers on two different levels. On the upper level, a certain amount of sunlight comes in to supplement the light from clear fluorescent tubes, and in addition, I have added one 100 watt bulb of incandescent light. On the lower level, immediately below, no light is provided except from clear fluorescent tubes.

I have not observed any difference in the growth of seedlings between the two locations. Perhaps if I were to make weighings or measurement, it might be possible to demonstrate a slight difference, but none is detectable by mere [visual] observation.

One other unexpected observation was made. I keep the lights on day and night, so that growth is continuous. I had read that when the lights are turned off, and then, after some hours, are turned on again, there is a considerable lapse of time before the plants respond and the chlorophyll becomes active. It seemed to me that the efficiency of my light would be greater if growth were continuous, and hence the policy of continuous lighting.

No disadvantage of continuous light has been evident, at least for seedlings. I am not prepared to say that that results might not be different for mature plants. It should not be forgotten that flower development in mature bulbs is dependent on them receiving a cold treatment prior to placing them under lights.

by Percy Wright (CPLS Newsletter # 9:4-5)