There is no question that at its core, UV light is harmful to plants. But in harming plants, it actually causes them to develop protective mechanisms that make them stronger going forward.
But what is the best way to give your plants ultraviolet light?
How To Provide UVA/UVB Lights For Plants
The main difference between reptile lights and black lights is that most reptile lights emit UV-B light (there are also UVA reptile lights, but reptiles need UVB more), while black lights emit UV-A light.
Black lights emit UV-A light only, so they affect plants the same way any other source of UV-A light does (which was covered above). They are a fairly weak source, however.
UVB LED Grow Light: Is It Worth It?
The problem is: it costs $499. For a supplemental light!
UV Light Reduces the Impact of Pests
At TSRgrow we are continually researching new technologies to incorporate into our TOTALgrow ™ Solution. Keeping in mind sustainability and efficacy when developing new products for our growers is always at the forefront of our process. Creating a UV light bar for our growers has been an exciting adventure and we are happy to be sharing this new product with you.
How Does UV Light Impact Plants?
Increase THC content
UV Grow Lights Empower Growers to Harness Nature
Ultraviolet light (UV) is a growing method to reduce pests’ impact, increase THC content, and accelerate the growth process. Artificial UV light allows growers to improve comparable plant quality of indoor cultivation without adding expensive synthetic chemical fertilizers.
Scientists surveyed cannabis strains that originated from different places around the world. They looked in places that had high UV levels (like near the equator, or on tall mountains) as well as places with low UV levels (away from the equator and in shady spots). They found that strains from the equator and high-altitude regions had more THC  .
UV wavelengths can also help plants defend against insects. UV wavelengths, and to some extent, other wavelengths of light, can trigger plants to release defence compounds. Some examples of these defence compounds are volatiles (smells that deter insects), hormones (alert defence responses in other parts of the plant), secondary metabolites (change the colour and taste of a plant) and trichomes . These compounds make a plant more distasteful or toxic to insects. As a result, plants with increased levels of these compounds get eaten less  !
UV Light May Increase Trichome Density and THC Content
Unfortunately, UV exposure is also connected with lower CBD levels. This is likely because there is a tradeoff between THC production and CBD production . To increase THC in the flowers of a cannabis plant, at least 1.34 Watt-seconds/m 2 of UV-B light is necessary. It should be given for 6 hours per day, for at least 40 days. Research shows that doing this increases Δ9-THC content from 2.5% to 3.2%  .
UV Light May Not be the Most Effective Way to Increase Trichomes
Growers who want to increase the potency of their cannabis may consider adding ultraviolet (UV) light to their grow setup. UV light is radiation with wavelengths between 100 – 400 nm and it’s not visible to the human eye. Outdoors, about 10% of the sun’s light is ultraviolet. Furthermore, UV light is broken down into several subtypes, including UV-A (315 – 400 nm), UV-B (280 – 315 nm), and UV-C (100 – 280 nm). Most lighting technology provides little UV light. So, to match the intensity of the sun, you would need a light that produces at least 32 W of UV radiation  A quick Google search shows that it’s not easy (or cheap) to find a light that can deliver this much light! And so this may make growers wonder: Are these lights worth the price? And — do cannabis plants even need UV light?