The following is an excerpt from an essay that first appeared in the American Orchid Society BULLETIN (what later became the current Orchids Magazine) in March 1981; the second in a many-part series on orchid growing for the beginner. At that time, the Society was headquartered at Harvard University, hence the references to the Cambridge offices. While much has changed in the intervening 28 years, including the society's headquarters, the general message remains the same.
You may have some difficulty, as I did, accepting the fact that orchids can be grown successfully under artificial light. The almost eerie gleam of fluorescent tubes seems far removed from the dynamic, natural environment in which orchids have evolved. To me, the whole idea suggested scenes from those futuristic science-fiction movies in which space-colony pioneers grow plants under artificial "suns" for survival in the void of black space. It was also hard to imagine sun-loving plants like orchids flowering under the relatively low light intensities of conventional fluorescent tubes. But flower they do. What fluorescent lights lack in intensity, they can compensate for in daily light duration and in numbers. After growing orchids under lights, and some research into what others with much more experience have written and done, I can now say that I am convinced.
The large numbers of "under lights" hobbyists is ample evidence in itself that artificial light is a fruitful means of growing orchids. Not only do many hobbyists consider growing their orchids indoors under lights an acceptable alternative until warmer weather returns in the spring, but a substantial proportion find the more controlled conditions and relatively minor costs of operation sufficient inducement to grow many of their orchids under lights all year around (see REFERENCES, entries 1, 2 and 3).
Lights, fistures and their supports
Because of the increasing use of artificial lighting, specialized fluorescent tubes and high-intensity lamps have been developed by the light-fixture industry for horticultural purposes. The array of both conventional and more innovative tubes and lamps on the market is a bit bewildering. Charles Marden Fitch, in his book, The Complete ok of Houseplants Under Lights (4), provides a helpful survey of the various lights, recommending, based on his many years of experience and experimenta-tion, the use of the broad-spectrum fluorescent tubes, or a combination of these and the standard "cool-white" tubes. Here at the A.O.S. Cambridge office, paphiopedilums and phalaenopsis flower quite satisfactorily under such a com-bination of lamps.
With the more recent, high-intensity lamps, light chambers can be created which virtually duplicate greenhouse conditions. One scenario scheduled to appear in the new A.O.S. film "The Many Worlds of Orchids" was one such "greenhouse," actually below ground level. Four high-intensity lamps mounted in the roof of the chamber produced light intensities approximating those of the outdoors on a sunny day. Orchids from many light-demanding genera thrived under humidity and light conditions comparable to those of a conventional greenhouse - yet they were spared the vagaries of the weather. Energy requirements for such lamps are not inordinately high, and you can be sure that the heating costs are insignificant compared to those of most greenhouses outdoors! (See REFERENCES, entry 5, for several articles on this innovative approach to light gardening.)
The type of lights most frequently used for orchids, however, are fluorescent tubes, usually 48 or 96 inches long, 40 and 74 watts respectively. If you want supplemental lighting for a less-than-sunny window, two such tubes will probably be adequate. For orchids depending entirely on artificial light, stick to a mini-mum of four fluorescent