| For quite some time i successfully grew and bloomed quite a number of Paphs, Phrags, Coelogyne, and other smaller-sized plants under 2 florescent tubes at a distance ranging from 6-12 inches. According to Maryes' Missouri numbers mentioned above, I should not have been able to bloom anything at all. This would seem to be a case where the numbers and what happens in practice (for one reason or another) simply don't line up.
For this reason I put very little stock in numbers for blooming orchids and find light descriptors (bright indirect light, partial shade, dappled sunlight, etc., etc.) to be much more practical. Even here in Australia I grow and bloom Cattleyas in a south window (equivelant to a Northern Hemisphere's north window) where they receive no direct sunlight at all. Buy the numbers on a light meter, I shouldn't be able to do this. I also find that many hobby growers given a choice of spending $100 on a light meter or $100 on plants would choose the plants 99% of the time. The numbers mean nothing to most.
Now I realize that we're talking about growing under lights in this thread and that means trying to approximate the effects of sunlight with something artificial, but even in these cases (for example 3 friends of mine who grow in their basements under lights) I find that people still frequently do not use light meters and instead try to compare their artificial light conditions to natural light.  |