From what I understand about LED grow lights from research I was doing on lighting systems about a year ago, is that, theoretically, they are the best system you can have, in that they can produce a pure blue or red light at the wavelength that is most conducive to photosynthesis.

But in practical application, they tend to fall short for several reasons. One is that the high powered LEDs, such as the 2 and 3 watt LEDs, seem to have a high tendency to burn out, or fry 1/2 the circuit board so only half of the fixture lights. Jumping off that, since you cannot really replace 1/2 a circuit board or individual LEDs, when theres a problem with your 300 dollar fixture, that problems there to stay after the trivial 1 year warranty expires (and even before that Ive heard that companies are loath to honor those warranties without making you jump through hoops (they know their stuff isnt going to last)).

Another is there very high initial cost per square foot of area covered relative to say MH/HPS. If I recall correctly, I remember a 300 dollar fixture I was looking at would cover a 2x3 square foot area, or 6 feet. The technicals looked tempting, even though the area was small, promising superior lighting conditions. But when looking at reviews for that product (and all other LEDs I could find), the most people were getting out of them was about 2 years; a far cry from the 50,000 hours advertised (which is why the warranties are only 1 year).

I ended up getting a 600w MH/HPS set up, which covers a 4x4 area, or 2.66 times as much as the LED area for only .66 the initial cost, and so far I am, and planning on continuing to be, very pleased with it.

What you could try doing is putting the light as close as it can get to the plants; one of the positives about LEDs is that very little heat is produced, making it safer than even fluorescent tubes to put the plants very close to the light source. But since your fixture is a 90 watt, Im guessing the individual LEDs are probably 1 watt or so apiece, right? That isnt going to provide much penetration power, so the light isnt going to seriously benefit anything other than the canopy of your plants. Which of course is better than nothing, but depending on your plants sizes and light requirements, the 90 watt LED fixture probably wont be making them explode with growth all on its own.

Also BTW, what colors is your LED fixture using? Ive seen some crazy products that throw in orange, purple, yellow, infrared, and UV LEDs in their fixtures to make them seem "more complete" I guess, but from what I can gather, all those extra colors that are not blue/red, are mostly or completely wasted, and is just a gimmick and power sap.

Thanks for that depressing commentary (-;

I really feel ripped off! It wouldn't have been quite so bad it this light hadn't been so expensive!

I guess I'll just lower the light and squeeze as many small plants together under it as I can; and hope for the best.

Don't get too depressed yet. Your lights are a bit high and definitely not on long enough. I know people that are running similar setups and are quite happy with them. You just might have been misled on how big of a footprint it will cover.

Try dropping the distance to about 10-12" above the canopy and running the lights for 14hrs.

Give it a try, you might be happy :)

I posted another comment over at the Cooking Forum.

dcarch

What plants are you trying to grow? Perhaps some plants respond better to artificial lights than others, but I am not sure about that. One thing I did when trying to grow a plant indoors in San Francisco was to put a mirror behind it, which reflected the natural light that it received. That made a huge difference in its growth.

Lars

I've lowered the light and increased the time to 14 hours; lets see what happens.

As for what plants I'm trying to grew; just houseplants and herbs. I've moved the herbs inside; to a south window that gets direct sunlight in the afternoon. I just lower the light onto a couple lettuce plants.