They backlight your glittering new phone and light up the dust on your trusty Burning Man bike; LEDs have wedged themselves into every facet of our lives, consuming more of our attention as the electronics that depend on them become omnipresent. They have now been developed to the point that they are quite useful for indoor horticulture operations, and therefore, weed. Though, that hasn't always been the case.
For a long time marijuana growers used a combination of metal halides — think big stadium lights — and high-pressure sodium (HPS) rigs. Under a blue-tinted light like that provided by halides, plants seems to develop their structure more readily, also described as its vegetative phase. Red tint — partially provided by the orange glow of HPS — encourages plants to develop flower more readily. This color cause-and-effect relationship is due to plants and their mechanism of photosynthesis. Green light would not absorb as readily and instead reflect off of green leaves.
So why all of the hubbub about LEDs for growing now? We have had red LEDs for decades, after all. They can be found as simple indicator lights in some of the first consumer electronics. Well, while we have had red LEDs, the blue ones were harder to manage. In fact, it was not until very recently they were viable. That is until last year when they became so rad that they garnered a Nobel Prize for NASA physicists.
LEDs will revolutionize the indoor growing industry with two major advantages now that they have become more accessible under decreasing costs. One factor is that that very specific and grow-optimum wavelengths can be achieved, blending blue and red light into the perfect shade of magenta. Another *huge* factor is their cost of operation. We have all heard of illegal grows getting busted because of traditional bulbs' energy suck and loss of efficiency due to heat. LEDs run cool, netting a savings of some 60% over traditional illumination — a big deal for a rapidly growing industry and home grows alike.
If LEDs are cool enough to grow the food for our astronauts, they should be cool enough for you.