>> I want to give some of the tender plants some light in the garage.
The following is my opinion from general reading plus some experience, mainly with vegetable and common flower seedlings. Maybe your tender plants are fussier than random seedlings.
Seedlings seem to do very well under average, generic fluorescent tubes. I think that using some "Daylight" or warm bulbs plus some "blue" or "cool" bulbs is plenty enough concern about spectrum to keep most plants happy. Light that is too "red" may tend to make some plants elongate. Flowering may respond to light color in some species.
i think that most
plants care much more about intensity (lumens or foot-candles or watts and efficiency) than they care about color spectrum.
If you're going to spend twice as much for fancy gro-tubes, buy a second fixture instead. T-5 or T-8 are a better investment than T-12 - more efficient for sure and probably brighter per dollar of purchase price.. And keep them clean and close to the plants, use reflectors, and replace the bulbs before they show black spots.
I did research it once and wrote up a blog post, but never turned it into an "Idea" article because I couldn't find good non-copyright images of spectra. And even after the reading, the 'spectrum" still sounded like opinions to me, and not opinions from horticultural experts.
I'm not any kind of expert, and I've never grown fancy, rare, tropical or demanding species.
http://garden.org/blogs/view/R...
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Broad spectrum tubes have tri-phosphor coatings to "spread out" narrow spectral peaks. They have a more uniform distribution of intensity all across the spectrum, instead of sharp peaks and low valleys.
I've read that really expensive grow-tubes are just moderately expensive "broad spectrum" tubes that were re-labeled with marketing claims.
Both broad spectrum and grow-tubes are less efficient, more expensive, and don't last as long as regular tubes.
It's debatable whether broad spectrum OR gro-tubes do any better for seedlings at all.
I believe that chlorophyll absorbs it all and turns it all into energy (except for the narrow green band that makes plants look green). But there may be seedling subtleties that I'm unaware of.
http://en.wikipedia.org/wiki/F...
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