So I have my 4 dwarf citrus trees (improved meyer lemon, mexican lime, oroblanco grapefruit, and trovita orange) in their containers. I have placed them in the sunniest location inside my house. I am planning on setting up a supplement light source to keep them growing inside in the winter. I live in the Birmingham, AL area and lately we have had a lot of cloudy days. I didn't want to purchase a HID lighting system due to cost, heat, and electricity consumption. I have been researching Par 38 LED grow lights, but I'm not sure what colors in the light spectrum would they respond to the best. Examples Red 660nm, Blue 450nm, Orange 630nm. Can anyone help me out? Thanks, Josh

I am overwintering all my Citrus under a simple Fluorescent work light in the cellar. It has 4 long tube bulbs of about 40w each.

I just wanted them to hang out and go dormant. Instead all of them are flushing and two have set fruit. Go figure.

Millet's HIDs would be the better choice, but were you to put mine over yours by a window, I would think they would do great. Won't cost much.

What kind of HID are you using millet? I Have a 250 watt MH lamp with some tomatoes under it and it starts to burn the leaves when it reaches about 4" under it. Another setup I have has a 400 watt HPS which is in a cool tube and I need to keep any plants atleast 6" under it or they start to burn.

LED need almost no energy and lasts 30 years ...
Besides they are now also super white like sunlight.

So that should be the best for your choice.

http://en.wikipedia.org/wiki/Light-emitting_diode

Excerpt :

Plant growers are interested in LEDs because they are more energy-efficient, emit less heat (can damage plants close to hot lamps), and can provide the optimum light frequency for plant growth and bloom periods compared to currently used grow lights: HPS (high-pressure sodium), metal-halide (MH) or CFL/low-energy. However, LEDs have not replaced these grow lights due to higher price. As mass production and LED kits develop, the LED products will become cheaper.

http://en.wikipedia.org/wiki/LED_lamp

Excerpt:

LED lights have also become very popular in gardening and agriculture by 2010. First used by NASA to grow plants in space, LEDs came into use for home and commercial applications for indoor horticulture (aka grow lights). The wavelengths of light emitted from LED lamps have been specifically tailored to supply light in the spectral range needed for chlorophyll absorption in plants, promoting growth while reducing wastage of energy by emitting minimal light at wavelengths that plants do not require. The red and blue wavelengths of the visible light spectrum are used for photosynthesis, so these are the colors almost always used in LED grow light panels.

You really shouldn't use wikipedia as a source. Its user edited, and often has a lot of opinion in it.

Just off the top, the first sentence has a couple of innacuracies: "are more energy-efficient, emit less heat "

LEDs have the potential to be more energy efficient, but as of right now, the best LEDs you're going to find in any sort of fixture are about 75 l/w. Some of the HID lights are in the 120+ range.

Now, CREE has produced some LEDs in the 150 l/w range, as has Seimens, but they're not commercially available yet, and it'll be a couple years before we get them to a reasonable price.

As to heat, the amount of heat something puts out is, in the long run, exactly equal to the amount of energy it takes in (especially when you're talking about light/heat sources). IE, 100w out of the outlet is 100w of heat into the room.

HID lights get HOTTER, but they do not produce more heat. They just have a higher temperature because they have a higher output per unit surface area.

The companies name is Siemens.

Find and read the scientifical reports about it, I do not have the time to find them for you.

Wikipedia has the benefit that it explains all easy, so that common people also understand it.

The energy used in your HID used is enourmous.
The heating effect may be nice in winter, but surely not in summer and can damage the plants.

The best for the plants are the specialized LEDs, for they produce just the frequencies of light, the plant needs.

LED lights are not there yet, a few years ago they came out and were horrible. The newest ones are much better than a few years ago but still not enough for a stand alone light to produce fruit. At the present they are only really good for vegetative growth and the price to buy them makes them not very economical.