Cannabis researchers in Maryland exposed pot plants to ultraviolet radiation to see what would happen. They found that increasing doses of UVB radiation, a natural part of sunlight, made the plants produce almost 28% more THC in the buds.
In attempting to understand more about the function cannabinoids serve, the scientists discovered a relatively simple way to increase potency by a great margin. They ran the UVB experiment on both high-CBD hemp and potent Jamaican marijuana to see if the cannabinoid content would increase. Curiously enough, while THC increased in the Jamaican weed, the Czechoslovakian hemp received from the University of Mississippi did not produce more CBD.
So UVB radiation plays a role in THC production, but cannabinoids as a whole still retain their mystique. One fact can’t be denied: UVB radiation increases THC in strains that already express high THC.
How to take advantage of the effect
UV light intensity increases significantly at higher altitudes; the best hash plants in the world are grown in mountains and elevated regions. According to the National Weather Service, UV light increases “4-5% for every 1000 feet ascended.” This means going from Phoenix to the top of the San Francisco Peaks increases UV radiation by 50%!
States like Arizona, New Mexico and Colorado receive some of the highest intensities of UV light with little cloud cover compared to northern states. Check out this map from the EPA to see your area.
Special fluorescent light bulbs generate radiation similar to natural UV light, and were used in the study. Growers put the plants under 40W Westinghouse FS-40 Sunlamps 10 inches from the canopy. Those exact light bulbs might be hard to find now, but similar, relatively inexpensive products are available in bulk and would be the best option for greenhouse-sized grows. The lights were filtered with cellulose acetate to remove the UVC spectrum—potent, damaging ultraviolet rays that are naturally filtered out by the ozone layer.
Micro and mini grow-ops can benefit from UVB supplementation, but need smaller bulbs. Desert reptiles like the bearded dragon require the radiation to make vitamin D, just as humans do. You can purchase a small UVB-emitting lamp at most pet stores. Mineral enthusiasts also use UVB lamps to make their rocks fluoresce, but the small handheld lamps are probably not potent enough for even a single plant.