Though I am not a plant grower (my wife is a master gardner) and have no experience with grow lamp, I have a bit of knowldge about lighting.

The LED that does not work for plant growing must be regular white LED which has very different light spectrum from sun light. Most of white LED has strong blue spectrum, and no IR, which does not provide necessary light spectrum for plant growth.

Regardless of its type (FL or LED), grow lamp is designed to imitate sun light which is essential for plant growth. So, it should work well.

Follwoing article is from WIKIPEDIA regarding LED grow lamp.

LED grow lamps

LED panel light source used in an experiment on plant growth by NASA. Pictured plant is a potato plant.
Recent advancements in LEDs have allowed for the production of relatively cheap, bright and long lasting grow lights that emit only the colors of light required for plant growth. These lights are attractive to indoor growers since they do not consume as much power, do not require ballasts, and produce a fraction of the heat of HID lamps. The lamps consist of arrays of many wide-spectrum red and a few narrow-spectrum blue LEDs of specific wavelengths. Although LED grow lights have shown promise through plant research by NASA and many universities, it is unknown whether the results are applicable to the cultivation of all plant-species, as their luminous efficiency is much lower.
However, luminous efficiency is not applicable to plant growth since it is based on what wavelengths humans see best. A plant is, for example very sensitive to far-red, while humans can barely see that wavelength. Therefore, LED's can be more efficient for plant growth, while their lumnious efficiency is lower compared to other solu

Go on over to the Growing under Lights forum. There have been lots of posts and debates over there, including some allegations that some of the posters are trying to drum up business.

I haven't tried them, I'm happy with my HID and fluorescents for now.

Hey there, I came across this page looking for different LED information but I want to try and set the record straight with a few misinformed people, or growers who tried LED's when they came for a few years and those who had poor results. Right now its still a bit of a secret that LED grow lights are giving pro results fast. Like most people, I tried LED 'grow lights' a few years ago when they came out and was highly disappointed. Although, its worth mentioning that ANY lighting you try will not work if you dont have the right spectrum/color temperature (measured in Kelvin 'K'). For most plants there are two stages, vegetative and flowering. Each plant has their stages a little different than another with some likeing short veg growth and long blooming growth, or visa versa. Most can agree on that veg growth requires a Kelvin 'K' temperature in the blue/white spectrum 6000k-7500K, and a blooming temp of 3000l-3500k in the red/orange/yellow spectrum. That goes for all plants and all lights. With that said the next reading on a light is the Color Rendering Index-CRI. The CRI index is a scale from 1-100 and it is how well that particular light Imitates the mid-day sun. there are no bulbs that can give you a CRI of 100, but some tweaked HID's can come close and now so can the LED's.

When they first came out they were in the right spectrum, but with poor watts/USABLE lumen ratios. Meaning that even though its bright, in the right color range, and cost effective. They werent in the form of usuable photosynthetic energy, just in the form of visable lights that humans can see and use. Now they changed that and some high-dollar LED's not only can be fine tuned better than HID(High Pressure Sodium/Mercury Halide) in the form of usable lumens and CRI index up to 99, and the best bulb ive seen in an HID system was a hybrid MH to HPS coming in at 96.

I was skeptical at first so i bought an expensive LED floodlight that had a usuable spectrum the same as visable lumens and rendered around a CRI of 90. It was in the 6300k range which is perfect for vegetative growth. I bought the expensive heavy bulb because if you experiment and go cheap then you will get what you pay for when it comes to lights. I was skeptical still so i surgically removed it from its packaging and it felt wierd using a floodlight bulb to grow stuff....it was like I was a sneaky teenager all over again, haha... Although after starting my plant from seed and after germination putting into my custom soil mix I went from Cotyledons (seedlings first pair of leaves that are similiar in every plant)to the second pair of true leaves in just 5 days with 2" of vertical growth. I have never....never seen that kind of growth in any of my previous plants I started from seeds. It could be that since I am becoming more skilled in my techniques of fertilizing and soil building, or maybe I was just lucky and had great genetics. So my second test is about to begin today and as a matter of fact I just ordered the expensive bright LED grow light that is 90Watts of power from LED's that are 2Watts each and the manufacturer claims that it can beat a 600Watt HID anyday. Once again my previous failure a few years ago has me suspicious but one thing is for sure. If my next seedling grows like my last super-grow-seed, Im switching my entire Florescent propagating lights out and switching to a row of those LED's.

BTW if your looking for decent lights that are low power consumers, that dont put out alot of heat, and are a sure fire way to grow indoors. Then your best bet is to find a used 4-6lamp(bulb) Flourescent ballast that uses the high output T-5 bulbs. Those have came a long way as well and work very well for small grows......hope it helps!~

-G

Yea. I know LED will not grow as good as a well cooled HID for a FACT. They are too expensive aswell.