uv lights for growing weed

Could UV Light Boost THC Production In Cannabis Plants?

Research shows a link between UV radiation and an increased THC content of marijuana. With this knowledge, we can increase our crop’s potency. Find out how to use UV light to produce potent weed!

The exact purpose and role that cannabinoids such as THC and CBD have in cannabis plants is still not entirely understood. Research, however, suggests that cannabinoids are a type of natural defence mechanism. It is believed that cannabis plants produce cannabinoids to ward off and defend against pests, diseases, and ultraviolet radiation. As such, recent studies have theorised that increasing UV exposure could cause more cannabinoid production in cannabis as a defensive measure – increasing potency and resin production.

We know that the most potent weed that grows naturally can be found in elevated mountainous areas around the world. Worthy to mention here, would be the growing hashish production areas in the Rif Mountains of Morocco, the Beqaa Valley of Lebanon, and the Hindu Kush. These areas have several noteworthy things in common: they are all close to the 30 °N latitude on the globe, they have the perfect marijuana-growing climate, an abundance of sunshine, and most importantly, they are located at high altitude. This means that plants receive substantially higher amounts of UV radiation – they higher you go, the greater the exposure. UVB is a part of the sun’s natural light, so all outdoors plants get it to some degree.

Knowing this, scientists have gone a step further. Researchers from Maryland did a comparison of cannabis plants grown with and without additional ultraviolet radiation exposure. It was found that certain cannabis strains that were already high in THC produced almost 28% more THC when exposed to UVB light. Oddly enough, the experiment did not lead to an increase of CBD in CBD-rich strains. These results strongly suggest a link between UVB radiation and THC, hinting at that increased THC production may play a role in protecting the plant from UV radiation.


Since we now know UVB radiation could greatly increase the potency of our crops, we can take advantage of this knowledge. With supplemental light bulbs that generate UVB radiation similar to natural UV light, we can supply greater amounts of UV light to our plants for increased potency.

Small and affordable UVB-emitting “reptile lights” can often be found in pet stores, as some reptiles need UV light. You can also do an internet search for those types of supplemental UV lamps. Some newer grow lights may even come with an integrated UV light. For the average micro or mini grow-op, those supplemental UV lights don’t have to be large. A single reptile light (or “desert light” as they are sometimes called) can be sufficient if you want to supplement some UV light to boost your crops’ THC content. Outdoors, there is little you can do to boost UV, other than grow up a mountain! Either way, the fact that UV could play an important role is an interesting discovery, showing just how much we still have to learn about this wondrous plant!

Can UV light boost THC in cannabis? Studies suggest a link between UV light exposure and THC production

Grow Hack: How to Use a UV Lamp to Increase THC

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.

Cannabis researchers in Maryland exposed pot plants to ultraviolet radiation to see what would happen. They found that increasing doses of UVB radiation, a