Cool White Bulbs (what I use):
I use multiple 40 watt 4 foot cool white fluorescent bulbs to light my seedlings. The bulbs cost less than $1.00 each. The fixture to run them is ordinary cheap 2 bulb shop light fixtures that can be found for less than 10 dollars. Because I start 400 plants I need eight of these (16 bulbs) arranged in an 9 foot by 5 foot rectangular block. Each fixture is suspended from the ceiling by chains for easy and individual adjustment as the plants grow.
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Each bulb (when new) outputs about 3000 lumens. 16 bulbs covering 45 square feet is around 1000 lumens per square foot – as long as the fixtures are kept low to the table. Of course light will be more intense in the center compared to the edges. I rotate plants every few days to give even light coverage per plant over the long term.
Grow Lux and Vita Lite bulbs:
These special bulbs produce a wider spectrum of light than the Cool Whites above. They are specifically manufactured to mimic more closely the sunlight spectrum – both for plant growth, aquarium lighting, and in the case of Vita-Lites for human mood improvement. They are also very expensive compared to the cool whites.
Years ago I did a side by side comparison of Vita-Lites, Grow Lux Wide Spectrum, and Cool White bulbs on my pepper seedlings. The end result was that I could see no difference between any of them (other than the significant cash outlay for the Vita-Lites and Gro-Lux).
There are many who are convinced that wide spectrum is better – and maybe a careful study could find some minor improvement – but I think that something that costs more than six times as much should show casually obvious improvements. I didn’t see any improvement at all. In fact, I would suggest that it would be better to spend the money on MORE LIGHT from cool white bulbs and fixtures rather than LESS BUT EXPENSIVE LIGHT from wide spectrum bulbs.
Other Fluorescent Bulbs:
There are bulbs that are labeled as “daylight” bulbs. These are also marketed as better approximating the solar spectrum (at least as far as the eye can tell), but actually looking at the spectrum shows a quite different story. In this case the energy is even more concentrated into narrow “lines” then the cool whites. Does this hurt the plants? I don’t know since I’ve not tried them, though the lumens output is usually smaller for the same power consumed and they are more expensive.
Same story with warm white lights. Nobody has recommended them and I haven’t tried them. They must be declining in popularity for any purpose since I can’t even find specs on light output for these.
