Although 10,000k and UV-A would probably provide decent growth, 6400K usually provides a good balance for plant chlorophyll absorption... less PAR spikes in the red wavelengths when using 10,000K.

UV-A usually falls in the 320-390nm range. Plants will use these wavelengths, but most growers believe their plants respond very favorably within the 400-700nm range.

Because of your question, I'm sure you are very familiar with Kelvin temperatures. Not all Kelvin temperatures (e.g. 6400K) provide the same spectrum. Different nanometer wavelengths can be used to reach the same Kelvin temperature (kind of like: 5+5=10, 6+4=10, 7+3=10, all producing the same same result of 10).

That is why LEDs are starting to become a popular choice with growing plants (allowing more choices, and having the ability to mix more colors to provide different plant spectrums). I think you will be okay with your idea of using a 3000/6400K mix. You could also add a 10,000k into your 3000/6400K combo and then observe to see if your plants respond favorably.

thanks for the info!! everything grows good now so I don't want to really mess with a good thing, but I know I will need more red spectrum when I transplant the plants from my garden outside to the green house in the basement.

I know the plants would grow with the 10K bulbs because I have two 10K bulbs in the HO T5 fixture on my 55 gal planted aquarium.

I do have one question you mentioned the believed favorable zone is 400-700nm. what spectrum does that fall out in kelvin wise?

Depends... for lack of better wording on my part.

Bulb manufacturers usually provide spectral distribution graphs that show how the bulb will output wavelengths, expressed as nanometers (or nm), and what intensities those wavelengths will emit. I have included an example: an older image of a 6500K GE starcoat spectral graph used for reference. Although very small and not the best of images, it will give you an idea as to the range and intensity of the 400-700nm zone this bulb emits (high spikes near the 440nm blue range, the 550nm green range, and the 620nm red range).

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Wow...interesting forum. Never been here before. I'm glad to see LED lightning becoming more common. I have an absolutely crazy use for it.

I want to be able to grow certain high elevation Chinese rhododendrons for the point of breeding with them, crossing them with very heat resistant species like R. hyperythrum so that their look can be imparted to plants that grow well in the eastern US. However, the summer climate here is too hot and wet and the plants die of phytophthrora.

My house has a small utility cellar that does not cover the whole foot print of the house. In other words, 2 of the walls are against several feet of earth, a third is exterior but mostly covered, and only 1 opens to the outside. It stays VERY cool down there as long as the door is kept shut. (the ceiling is poured concrete, too, I think they wanted it to be fire proof in case the boiler exploded!) I think it would be a perfect place to set up a long term, air-conditioned grow facility. Yes it would still have be air conditioned in summer. I'm thinking of a using a portable 2 hose computer room chiller. They are expensive but can put out a _lot_ of a cold air. Ideal temp range will be about 70 day, 55 night. HID would just heat things up too much. I'm even thinking of building my own rectifier and running heavy low voltage DC AL wiring into the space, so that the heat of the rectifier doesn't warm the space too much. FWIW Longwood Gardens has a fully air-conditioned conservatory, getting natural light, for growing other, similar alpine plants. It has to cost a future to keep cool and admittance is only to staff, not public visitors.

BTW I just posted to this thread because it seemed to be an active one...let me know if you have any feedback or thoughts. Or not, whatever. I doubt many people build their own power supplies but I do electronics tinkering and have built my own audio amp and repaired a couple others so I think I could handle it. Of course, switching power supplies are so cheap and efficient, I might just use a whole bunch of them bought as ready-made boards, parallel them, and build my own improved current and voltage regulation section. Or maybe someone makes a reliable remote ballast/PS unit.