Led is extremely useful for growing cannabis. Cannabis blooming requires 12 hours of darkness for the Pyr r to Pyr fr conversion to take place. This conversion is promoted by exposure of the plant to Red light at the wavelength of 730 nm. I was able to find an ebay led merchant that was actually a factory outlet from Hong Kong or China. He did a CUSTOM RUN for me, for a bag of 1000 730nm wavelength LED's for $100 US. You then have to find someone, or learn how to solder these LED s to a
perforated board (available from Radio Shack, or whatever it's called now, or other electrical supply store) Basically you just need an AC adapter for the power supply, some resistors in series with the LED's wired in series/parallel arrangement, to make
a small panel of 730 nm. wavelength LED's. I only used about 50 LED's, and illuminated my garden with it for about a minute at the beginning of the dark period. A FLASH of this light at the BEGINNING of the period of darkness, will immediately convert Pyr to Pyr fr, which is what she needs to signal her to bud. Then, she will only need 8 hours of dark instead of 12 hours. This allows for more yield, because now you have 16 hours of light per day instead of 12 hours. I found this out, by doing a google search for photomorphogenesis. Some of the articles that I found out back when are no longer available, however I did use this method and it worked well.
The above post is for entertainment purposes only, since I do not grow pot, and do not advocate breaking the law.