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Whenever cultivators ask my opinion on a problem they are experiencing in their facilities, I always am cautious to answer. I try to make it clear when my feedback is only based on observation of repeated results, and that my opinion may be proven wrong by valid scientific data.

As much as I try to provide factual information, I have, over the past few decades, made a few (unwitting) mistakes in doling out advice to cultivators. There are two perfect examples in my book “Marijuana Horticulture Fundamentals” published in 2015. The first example is about lighting.

Shining a Light on UVB

In my book, I wrote about the potential of ultraviolet B (UVB) lighting to increase THC production, a claim that had gained traction among many legacy growers after early studies seemingly pointed to the correlation:

“Knowledgeable scientists have published many articles pertaining to the benefits of UVB light rays on plants, and cannabis plants in particular,” I wrote. “Many acknowledge that plants grown at high altitudes produce more THC via larger trichome heads. If you took two identical plants and grew them under identical conditions, except one was grown at a [5,000- to 6,000-foot] elevation and the other at sea level, the plant that was grown at high elevation would be superior to the sea level plant in terms of THC content. Some attribute the difference to the drastic temperature differential between day and night at such altitudes;”

I then state:

“I do not believe this to be so. This no doubt has something to do with it, but I believe the increased UVB exposure is the primary cause of the plants increased THC productivity. […]Increased UVB exposure triggers the plants[’] survival responses[,] and it responds by producing more oil and resin, which are then pumped into the glands in an effort to make the trichome heads larger and so act as a form of sunscreen. The bigger and more resin glands there are, the less UVB, UVA and UVC will be exposed to the plants[’] surface. Black lights emit ultraviolet (UV) light but are unacceptable for plant growth, as are UVB enhancers added to existing lighting.”

I do hedge my statement by noting “that there has been no formal compilation of scientific data to confirm this theory regarding UV light as true, and it is only mere speculation at this point. Hopefully in the future we will compile true data on this subject and either prove or disprove the theory once and for all.”

The RIPS Papers are an annotated collection of cannabis research assembled by the Research Institute of Pharmaceutical Sciences at the University of Mississippi and have been published since the 1980s.
Photo by Kenneth Morrow

So, how much do I believe in the possibilities of UVB enhancement? Well, I have a patent filed on using UVB light in this exact way (see United States patent #7905052 titled “System of photomorphogenically enhancing plants”). From where did all the focus on UVB and THC production come?

For me it all started with the Research Institute of Pharmaceutical Sciences (RIPS) papers from the University of Mississippi. The institute was established in 1964 to discover and disseminate knowledge of natural products, and the RIPS papers have been published since the early 1980s. I compiled the many volumes of the RIPS papers into a personal book of dozens of studies concluding that there is an increase in THC production when UVB light is applied.

As a whole, the studies compiled in the book represent tens of thousands of dollars and hours of very legitimate research, which boast a very impressive list of scientists who conducted the research and wrote the papers. However, much to the lament of anyone who attempts to re-create the increase of THC production via application of UVB light, the results have proven difficult to repeat outside of lab settings.

That’s not the only lighting belief I’ve held that has since been proven inaccurate. In the January 2008 issue of Skunk magazine, the author of the article titled “Hash Tips: Maximum Resin Production for the Medical Cultivator” claimed (through testing multiple lighting systems) that it is important that lighting fixtures have 660nm of red spectrum and no traces of 680 nanometers (nm) red. “Absorption peaks around 660nm for red and flowering is inhibited at around 680nm red… [The] HPS spectrum contains 680nm red. This inhibits flowering just enough so that resin concentrations are standardized.”

The author continues: “Metal halides are also sometimes used during flowering to promote resin production. This effect is from the UVB light that exists in halides. Halides contain 680 nm red and will not achieve the concentration we’re looking for. Only in high concentrations of 660nm—without the 680nm red—can the cannabis buds reach a point closer to genetic perfection.”

However, according to Université Laval professor Dr. James Eaves, Ph.D., who has studied light spectrum’s influence on cannabis production, “when we consider the impact of particular wavelengths, like R [red] and FR [far red], what’s important are ratios (e.g., R/FR, B [blue]/R, B/G [green]), rather than occurrence of individual wavelengths (e.g., 680 nm). For instance, R causes cell expansion while B reduces it, so it’s B/R that impacts plant development.”

This goes to show that despite how lighting’s impact on cannabis chemistry is one of the most researched topics in the cannabis space today, much more work needs to be done to further investigate how it plays out in the field in order to correct the public record.

According to Dr. James Eaves, the ratios of far red, red and other light wavelengths are more important than occurrence of individual wavelengths (e.g., 680 nm).
Fukume | Adobe Stock;

Humming on Humic Acid

The second “best practice” that was eventually disproven in my book relates to the use and application of humic acid on cannabis plants—more specifically, humic acid derived from pure, mined mineral-rich organic plant active humates. (Humates have been shown to regulate the flow and enhance the transport of nutrients for some plants in certain cropping/growing systems.) In my book, I mention a commercial form of humic acid advertised as “[accelerating] nutrient absorption at the root boundary zone, where minerals enter the plant,” which continued into “Excellent for indoor and outdoor use.”

For a grower like myself focused on healthy plant growth, all these promises sounded fantastic and logical. Humic acid has been used on other crops for the purpose of increasing nutrient uptake and stimulating plant growth—why wouldn’t it work for cannabis?

While it is true concerning many other plants, it seems humic acid may have unwanted effects on the cannabis plant. A June 2019 study published in Frontiers in Plant Science titled “Impact of N,P,K, and Humic Acid Supplementation on the Chemical Profile of Medical Cannabis (Cannabis sativa L)” sheds light on the fact that humic acid impacts cannabis in more ways than just overall plant health.

Among other findings, the authors discovered that humic acid “was found to reduce the natural spatial variability of all the cannabinoids studied. However, the increased uniformity came at the expense of the higher levels of cannabinoids at the top of the plants, and THC and CBD were reduced by 37% and 39%, respectively.”

I mention humic acid because once upon a time it was thought of as a beneficial enhancement. But when applied to the cannabis plant, humic acid, at least according to this most recent study, can negatively impact cannabinoid production.

In turn, this finding also makes me question the use and application of fulvic acid on cannabis plants. Fulvic acid is thought to accentuate the production of nucleic acids and photosynthesis—and even made an appearance in my book: “Fulvic Acid will supercharge the entire plant from the roots to the growing tips,” I wrote.

Now I’m left to wonder whether, like humic acid, fulvic acid comes with drawbacks when applied to cannabis plants?

Perhaps in the future, data such as this will be utilized to purposely produce or manipulate certain desired cannabinoids or terpenes. There is much to prove and disprove regarding cannabis and its production. And with more and more researchers turning their attention to cannabis, it is no surprise that some things that once were considered to be true have now been proven false.

Perhaps we should take the time to re-evaluate how we’ve come to some of our conclusions, and whether that certainty is warranted. The way I test myself when I form an opinion is to immediately attempt to prove myself wrong. But even if a given opinion survives thorough scrutiny, it remains an opinion until scientific data can support the claim and is repeatable in the real world, not just a lab.

Kenneth Morrow is an author, consultant and owner of Trichome Technologies. Facebook: TrichomeTechnologies Instagram: Trichome Technologies k.trichometechnologies@gmail.com