Photo illustration: Elena Scotti/GMG, photos via Shutterstock

The feds began monitoring the potency of the nation’s pot supply in the ‘70s by drawing samples from stashes seized by law enforcement, and boy was it schwag. The percentage of THC—the main psychoactive component in cannabis—averaged from less than 1% in 1975 to just under 3% a decade later, according to the data. These notoriously low levels reflected the times, as the weed subculture in America was just starting to take root and could help explain why some of the most memorable old school brands have names like Acapulco Gold, Panama Red, Afghani, Thai stick, and Jamaican sensi; they were all originally cultivated outside of the country.


Now, as some critics have pointed out, it’s impossible to empirically confirm how strong domestically grown pot was back in the day due to inferior testing and sampling methods, however, there does seem to be enough prevailing research, firsthand testimony, and common sense to show that the illicit reefer from decades ago wasn’t nearly as powerful as today’s. Even if we account for the inordinate amount of Mexican brick weed that’s said to have dragged down national averages, the percentage of THC was still remarkably low across the boards well into the late 1990’s.

A recent federal study found that “the potency of illicit cannabis plant material has consistently risen over time since 1995 from approximately 4% in 1995 to approximately 12% in 2014.” This marked increase represents a shift when smokers began to pivot from dirt to mid-grade and hydro. In one standout bust from 2009, the DEA nabbed some sticky-icky that scored an impressive 33.12%, the highest concentration of THC the agency has ever seen in a domestic sample of weed. Keep in mind, the government stats don’t include samples from the “legal” market, where flowers—a common euphemism for buds—have tested way above 20% and even upper 30%, with cannabis concentrates soaring into the 90% range, a remarkable achievement in human history. Generally speaking, anything over 15% is considered good shit.


There’s also the less scientific method of examining photos of buds from early issues of High Times, since you can also tell a lot about cannabis from how it looks. The visual evidence suggests that the “grass” in the free love era—including the stuff Bob Marley smoked—lacked the characteristics associated with the quality found in today’s headier brands like Girl Scout Cookies, Bruce Banner, and Gorilla Glue. Many of the nostalgic strains didn’t have large concentrations of trichomes, the crystal-like resin glands that are very identifiable in photos and which have come to define modern day chronic. The old school buds were also stringy and brown. By all accounts, it looked inferior, because it was.



This week on Giz Asks, we asked the DEA, weed dispensaries, cannabis cultivators and an esteemed professor who has been growing weed for the federal government for the past few decades, why cannabis is getting so potent.

Mahmoud A. ElSohly, Ph.D.

Professor of Pharmaceutics in the School of Pharmacy at the University of Mississippi, Director of the Marijuana Project at the University of Mississippi. For the past few decades, he has been growing weed for the federal government at the only legally-permitted weed farm on the Ole Miss campus.

The answer to your question in my opinion lies in several facts: 1) The cultivation practices in the cannabis industry has moved into the production of sinsemilla as the preferred product. Sinsemilla is the product generated from the flowering tops of female plants that have not been fertilized. It is the part of cannabis plant with the highest THC content. 2) The trimming of the cannabis products (sinsemilla or buds) and removal of all large leaves which have low levels of THC. 3) Selection of high THC varieties or strains for high cash value. 4) THC is known to produce tolerance in frequent users. Therefore the more one uses marijuana the more THC one needs to achieve the same degree of high one once had. So the users demand more marijuana or higher THC content.


Derek Peterson

CEO of Terra Tech California-based, publicly traded cannabis company (TRTC) that grows, markets and retails cannabis

Over the last decade, potencies in cannabis have risen sharply because of the adaptation of the plant sciences that have migrated from traditional agriculture into the cannabis scene. A major driver in the increased presence of cannabinoids is primarily due to better breeding, strain-crossing as well as tissue culturing. However the plant’s genetic makeup is just one component. In addition, we’ve seen an increase in scientific and data based plant cultivation techniques. Essentially, the combination of better genetics coupled with more advanced cultivation techniques have led to a higher quality end product. We believe this trend will continue over the coming years.


Morgan Fox

Spokesperson for Marijuana Policy Project, an influential lobby group focusing on reforming federal law so states can decide legalization

Marijuana has gotten more potent over the last few decades for several reasons. The first is prohibition. By breeding marijuana to be more potent, less must be consumed to achieve the desired results, which means that there is less to grow, transport, or hide illegally. The same thing happened during alcohol prohibition. Hard liquors became much more popular because it was easier to move and hide from authorities. Another reason is customer demand and safety. The more potent marijuana is, the less people have to smoke, which is easier on the lungs. The popularization of vaporizing marijuana also creates more demand for higher potency since this process works better with higher-density cannabinoids. The increase in patients using marijuana for medical purposes has also driven a huge increase in THC and other compounds through selective breeding and the development of concentrates. Many patients need instant, powerful pain relief that is much harder for them to achieve with low-potency marijuana.


Sally Vander Veer

President of Medicine Man, Denver dispensary that carries highly potent cannabis strains for recreational and medicinal use

1) Consumer demand. Contemporary market forces are pushing a “higher THC is better” approach to cannabis breeding. Cultivators have access to more science, better nutrients, more information, and are cross-breeding strains for increased potency which typically results in increased profits. What a majority of consumers do not understand is that higher THC-A percentage strains do not necessarily equate to a bigger or better high. There are over 500 components of the cannabis plant which contribute to each unique high associated with that strain, THC being the largest part of that high, but certainly not the only determining factor. Our top selling strains at Medicine Man in the last year, Girl Scout Cookies and East Coast Sour Diesel, are both testing around 20% THC-A. Customers come back for these particular strains (even after trying the higher testing strains) for their flavor, smell, taste, appearance and overall effect in spite of their average potency. 2) Better testing. We now have dedicated testing labs for cannabis and as such, the methodologies and sensitivity of potency tests have improved significantly. There were limitations on old testing methods which relied primarily on gas chromatography which heats test material before analysis. This heat alters the chemical profile of cannabis, including the breakdown of the THC-A molecule. One would expect an increase in potency with an increase in testing sophistication. This probably does not account for a huge jump in potency, but must be considered when discussing the topic. The cool thing is that as we approach the maximum threshold of THC-A in our strains, consumers are catching on to the importance of other plant components, namely terpenes and other lesser studied cannabinoids, and I see a focus on the whole plant composition as the next great cannabis frontier.


Rusty Payne

Spokesman for the Drug Enforcement Agency, the federal law enforcement entity that has been busting people and providing government agencies with samples of seized cannabis for decades

In short, marijuana is more potent because the quality of the cultivation process has been enhanced by hydroponic lighting, as well as THC extraction which creates a much more potent product.


Jesse Henry

Executive Director of Barbary Coast Collective, a San Francisco dispensary that carries potent cannabis for medicinal use

Cannabis is getting more and more potent because it’s getting more specialized for specific needs. At the same time cannabis is getting less and less potent for the same reason. Some patients need high thc and others need high cbd. Same goes for thca, thcv, cbn and cbg to name a few.


Stephen Gardner

CMO of Tikun Olam, Israeli-based cannabis company that grows medicinal cannabis strains

It truly has to do with the way it has been unregulated in the black market environment. That you have people who are taking great risks and therefore they’re looking towards ensuring that they’re getting the greatest yield and the greatest potency for market demand. On your grow you want to get more bang for your buck.


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