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.
How to take advantage of the effect
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.
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.
No, most plants can not grow under a black light, if the black light is the only light source. If other light is present, they can grow under the black light, assuming it is not too strong or close to the plants. The black light itself does not do anything to help growth, though.
The only way adding UVB makes financial sense is to get a regular T5 fluorescent fixture and put a T5 fluorescent UVB bulb in it.
With weed, this results in an increase in THC and CBD. For this reason, feeding your marijuana plants low levels of supplemental UV light will actually help them and generally result in better crops, as is the case with cannabis.
For that reason, any LED grow light that has UV diodes will work just fine to give your plants some UV light.
Black Light For Growing Weed?
And you pay for this addition. There are only two of these lights on the market: the Amare Solar Eclipse 500, which costs $1075 and the California Lightworks SolarSystem 1100 with UVB, which costs $1799.
While UV light is generally harmful to plants, it can still be used to bring about positive effects. A final such effect comes in the growing of cannabis.
Ultraviolet light causes the production of resin, and with it THC and CBD, in order to protect the marijuana plant from harmful UV rays. Thus, adding UV light to LED grow lights results in an increase in THC in the resulting buds.
Can Plants Grow Under Black Light?
Then there is the Cirrus UVB bar. It is the only fixture that uses actual UVB diodes. And it uses only those diodes. It is a pure UVB LED grow light, meaning it functions as supplemental lighting only.
Plants, like humans, are living organisms.
Finally, UVA and near ultraviolet light (315-400nm) has the longest wavelengths of UV light and can be very beneficial to plant development. UVA has also been shown to increase the amounts of THC, CBD, and terpene production in cannabis plants, without the negative effects of UVB. Wavelengths in the UVA spectral range are included in the absorption spectrum, particularly in the 380nm range. The absorption spectrum is the range of wavelengths of light that are absorbed by green chlorophyll for photosynthesis. Additionally, research has shown that exposing plants to UVA light can also inhibit mold growth and fungal development.
Many of the spectrum wavelength ranges I mention above are visible to the human eye, but plants require wavelengths above and below the visual spectrum of light that includes ultraviolet (<400nm) and far-red/infrared (>700nm).
The appropriate amounts of far-red and infrared light can also be a very effective at promoting robust stem growth, proper node spacing, and more flowers and fruit. Too much IR radiation can also be an issue because to plant the majority of IR radiation is felt as heat. Growers who use traditional 1000W HPS lighting, which produces excess heat through IR radiation, have to install and operate expensive HVAC systems to mitigate the heat. Too much IR radiation can cause plants to stretch spreading out the plant nodes, can discolor the leaves or even kill the plants. Choosing a light with the right appropriate amount of far-red and infrared light is key for healthy and natural plant growth.
Far-Red and Infrared Light
UVB (280-315nm) has a short wavelength, high energy and also causes sunburn in humans and plants. UVB is known to damage protein and nucleic acids in plant cells, causing decreased metabolism and decreased number of flowers. UVB can have positive effects for plants as well. Cannabis responds to the stress and sunburn from UVB wavelengths, by creating it’s own sunscreen in the form of trichomes. The more trichome production the higher the THC, CBN and CBD levels.
Exposure to UVB radiation is also known to reduce a plants biomass, plant height and leaf area, but increase leaf thickness, terpene and resin production. Cannabis cultivators who’s main goal is to boost the amount of fragrant enhancing terpenes and oils for edible, tincture or waxes, rather than focus on high yields may choose lighting such as Metal Halide that provides some level of UVB radiation or supplement their current lighting with UVB reptile lights.
Ultraviolet Light (UV)
Ultraviolet light is comprised of three different wavelength ranges of light. UVC (200-280nm) has the shortest wavelength and most energy, but is potentially the most stressful to plants and human skin causing sunburn and can be very damaging to human eyes. Fortunately, for humans and plants atmospheric absorption eliminates the majority of UVC shortwave light.