Many growers have long suspected a relationship between cannabis and UVB light. It is well-known that cannabis produces THC primarily as a natural UVB filter. Most psychoactive cannabis varieties originate from regions near the equator or high elevations where UVB levels from the sun are very high. In contrast, cannabis grown in areas further north or south of the equator, which have lower UVB levels, tends to be non-psychoactive and is classified as hemp.
Cannabis plants produce THC as a response to UVB light exposure. When the plant senses a UVB level above a certain threshold, it triggers the production of THC, which serves as a protective filter for the plant's trichomes. This mechanism helps protect the plant's reproductive cycle from UVB damage.
California LightWorks has developed supplemental UVB lights specifically for this purpose. These lights are used during the last two to three weeks of the bloom phase when flower, resin, and trichome development occur. By introducing higher levels of UVB during this period, growers can increase THC levels and improve the overall chemical profile of the plants.
LEDs are generally inefficient in producing UVB light. Instead, California LightWorks uses custom-designed fluorescent bulbs with high UVB output. These bulbs are designed to be placed about three feet above the canopy, covering a four by four space. They also feature a special warning light to indicate when they are on, as the UVB light itself is not highly visible.
These UVB lights are available as individual units or as part of a kit, which includes brackets and two UVB lights for optimal coverage. It is not recommended to use UVB lights throughout the entire growth cycle. Instead, they should be used only during the last two to three weeks of flowering. Additionally, the UVB lights do not need to be on for the entire 12-hour light cycle and can be run for about six hours, typically during the last part of the light cycle.
The UVB lights should be on a separate timer and power cycle from the main LED lights. They are also chainable, allowing up to 20 units to be daisy-chained together, with automatic voltage recognition for 120 or 240 volts. This setup can run a long string of UVB lights from a single power outlet on a single timer.
It's important to note that UVB light is dangerous and can cause sunburn and eye damage. Since the UVB light does not produce much visible light, it might not seem intense, but it is quite strong. Therefore, it is essential to avoid working under the UVB lights or even being in the room while they are on. The lights should be turned on only when no one is in the room and controlled by a separate timer.