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Is A Black light For Growing Weed Worth a Try?

Are Black Lights Good For Growing Weed?

Blacklights or UV lights are somewhat controversial in the cannabis community. Some growers believe that using a black light will result in stronger weed. On the other hand, skeptics, rightfully so, stated that there is not any scientific proof that a black light increases weed’s strength.

Because cannabis is illegal federally in the US, there have been very few studies on its cultivation. As a result, the only proof was a grower stating that UV lights did help the overall quality of their cops. So, the question that needs to be asked is:

Is using blacklights for growing weed recommended, or should you just stick to regular grow lights?

Black Lights are the same as ultraviolet light. (UV A to be exact) For variety, UV and black lights will be used interchangeably throughout this article. Although it is not technically correct. Many people think that all UV light spectrums are the same. Therefore, they do not differentiate UVA, UVB, or UVC rays. Because of this, you should assume, in this post, that any ultraviolet light spectrum to considered to be a black light.

Black Lights, (“UV Lights Background”)

In previous posts, I’ve gone over grow lights’ role in the light spectrum. Click Here, if you need a review. So, I will only go over the UV electromagnetic spectrum.

UV is short for ultraviolet radiation, and it comes from sunlight. There are three forms of UV electromagnetic waves:

  • UV-A
  • UV-B
  • UV-C

UVC light is damaging to life forms and because of the earth’s protective ozone layer, the damaging rays do not reach the earth. UVA and UVB though do reach the earth. UV A and C exposure can cause skin cancer and also damage plants. However, as long as it isn’t overdone, UV can make cannabis stronger.

The following video, by NASA, is an excellent overview of the UV light spectrum.


Are UV Lights Mandatory for Growing Weed?

No, UV lights are not mandatory. You can grow perfectly normal and excellent crops without UV lights. Plants need red and blue lights for growth. However, you do not need a UV light to grow weed. A UV light is called supplementary for a reason, in that they are designed to complement other grow lights and will not work on their own in cannabis cultivation.

Are Black Lights Good For Growing Weed?

As stated earlier, UVA or UVB lights have never been scientifically proven to help increase THC levels for cannabis plants. Recently, with the increasing acceptance of weed, there have now been scientific studies showing that UV rays can, in fact, help increase weed’s THC percentage. I will get to this later. But, I would first like to go into the history of UV lights and weed.

How Was UV Lighting for Weed Discovered?

Historically, before cannabis became commercialized, the highest THC content in weed strains came from countries that were in the highest elevations. The higher the elevation, the more UV rays reach the earth The pioneers of medical cannabis theorized that using a black light, which emits UV lights, would result in stronger crops, which was followed by an experiment by testing UV supplemental grow lights on cannabis plants. Their experiment resulted in the black lights substantially raising the THC level. In fact, growers who use UV lighting have reached up to 30% more than when a black light was not used.

These findings although promising were, as cannabis was nearly impossible to study, not scientifically proven. However, with weeds increasing acceptance, cannabis is now being studied by research institutions. One such study, from Maryland, has shown that UVB on average will help increase the levels to around 28%. There also have been studies that indicated that UVA lighting will also increase THC levels.

Does UV Help With CBD?

Unfortunately, No. At least according to these studies, these same studies, concerning UV lights did not show any increase in CBD levels.

In Theory, How Does UV Lighting Make Weed Stronger?

UV rays, as they damage the human skin, also damage plants. Cannabis’s reaction to UV rays is similar to the human’s reaction to damaging UV sunlight. Human skin, hit by sunrays, as a form of self-protection, forms a tan. Likewise, cannabis when hit by UV rays, as a self-defense mechanism will start to produce more trichomes, and more trichomes equal higher THC.

Can You Grow Weed With A Black Light?

UV lights have been shown to be not just promising when it comes to raising the THC percentage in plants. It has also shown to have promise in helping out with the following:

  • CBD-Increase CBD levels. This though at least by the Maryland study, has not been scientifically proven.
  • Quality-Enhances the taste and smell.
  • PLant structure-Helps a plant develop more branches and less stretching.
  • Resistance-Plants have shown to be more resistant to insects, fungus, and pests.

Best Practices for Growing With Black Lights

When used correctly, using a backlight will make it easier for you to grow quality weed.  However, if you decide to use a black light for growing weed, you need to remember that UV lights can also be damaging. Producing more trichomes is cannabis’s natural means of self-defense from UV light rays. Granted, more trichomes means stronger weed. But, the UV rays are still damaging your plants. This means that you can overdo it with UV rays and damage your prized crops’ beyond repair. So, you need to make sure that blacklights are intelligently used.

What Type of Black Light Should I Use?

There is quite a bit of mixed information on what types of black lighting is appropriate. For example, a few reputable authorities state that you do not need to purchase fancy, UV grow lights, and a simple UV reptile light will do just fine. However, others state that not just any UV light spectrum will do and that their specific black light is designed to give you the best results.

Of course, grow light manufacturers recommend specialized and expensive black lights. So, I am skeptical when it comes to their advice. And, the one that recommended a plain lizard lamp is the highly respected Royal Queen Seeds. As a result, if your current lights do not feature UV, a reptile lamp should be sufficient.

WACOOL Reptile Light Fixture Deep Dome Dual Lamp Fixture, Tropical UVB Light Reptile Heat Lamp Kit Combo Holder, Premium Reptile Reflector with 2 Indenpent Switches, 2 Bulbs Supported

Many growers use reptile lamps for their UVB lights

All In One Option

Black lights commonly included with both high-end and lower-priced full spectrum LED grow lights. For example, California Lightworks that are considered among the best has built-in UVB lights. Also, __________, which is quite cheaper also offers black lights.  Also, cheaper LED grow lights have, built-in, UV.   So, you should consider buying a LED system that already has black lights.


1000W LED Grow Light, CXhome Full Spectrum LED Plant Grow Lamp with UV&IR, Dual-Chip Growing Lamp with ON/Off Switch, Daisy Chain for Hydroponic Veg and Flower

This Lower-Priced Grow Light Has UV Capabilities

UVB Lighting Systems

You also may want to consider a separate UVB grow light system..  California Lightworks is a prime example of one and is shown below.

California Light Works CLW0053 UVB Grow Light System

 This one costs more than most lower-priced LED lights. So, I would spend your money first on a top of line, LED, grow light first. 

Final Thoughts

Based upon the recent studies and also its proven track record blacklights can help you grow stronger cannabis plants. However, using a black light for growing weed, when it is done wrong can also damage your crops. New growers need to keep it simple when they are just starting out. So, I would grow at least one cycle before you add black lights. But, for those that are experienced, I would definitely give it a try.


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