PGR Weed is Risky and Here’s How To Spot It

Francis Cassidy September 24, 2019 7 comments

What is PGR weed? And why you should avoid it.

Unscrupulous growers use PGRs to increase the bottom line. Adding Plant Growth Regulators (PGR) to cannabis is one way to create the tight, dense weed nugs that appeal to customers. But, it’s been chemically treated and has lost some of its medicinal value. The most common PGRs are:

Paclobutrazol – stops plant from grow so it focuses on buds. Lowers terpenes and THC.
Daminozide – to increase bud yield. Lowers terpenes and many cannabinoids. Carcinogenic
Chlormequat Chloride – creates bushier plants with more flower. Toxic in large doses.

What Are PGRs (Plant Growth Regulators)?

Using PGRs — or plant growth regulators — helps to control the growth of plants. In cannabis, these are a cheap additive used to fatten up buds to increase both weight and density, and hence inflate the price to deceive unwitting consumers.

PGRs greatly benefit unscrupulous growers, but much more worrying is the effect they can have on the health of consumers. There are confirmed links between adverse health effects and PGR use.

What Are the Most Commonly-Used PGRs?

Many types of PGRs aid in the control of plant growth across many species. However, when it comes to cannabis cultivation, the three main types typically in use are paclobutrazol, daminozide, and chlormequat chloride.


Paclobutrazol is a plant growth retardant that functions as a gibberellic acid antagonist. By binding to certain enzymes, paclobutrazol reduces the ability of the plant to synthesize terpenes. It also reduces the ability of the plant to produce the all-important intoxiating compound THC.

Fewer terpenes and lower quantities of THC only serve to diminish the many medicinal properties of the cannabis plant. As a result of this the entourage effect — the synergies that play out between plant compounds — can’t take place as nature intended since all the compounds aren’t present.

But what’s of most interest to the immoral growers who use it is that paclobutrazol hinders the ability of cells to elongate. This results in cells that pack tightly for increased density and weight in the buds.

When buds which contains paclobutrazol are smoked, it breaks down into nitrosamines — the most carcinogenic compound found in cigarettes. Studies say paclobutrazol can negatively impact fertility in males as well as cause liver damage.

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Back in 1999, the U.S. banned daminozide — or alar — in consumable plants. The ban came about when researchers showed that the product is a human carcinogen. The cultivators who use it do so for its ability to inhibit the gibberellin pathway in ornamental plants. When use on cannabis, the result is a reduction in terpene production along with a reduction in the production of major cannabinoids like THC, CBN, and CBD. In effect, there’s lower quality when it comes to the all-important resin production. So the quality of any resulting medicinal benefits becomes greatly diminished.

The chemical maximizes bud yield by slowing the growth of leaves and stems.

Researchers will not approve it for food products, therefore, consumers should NOT smoke or ingest it. Daminozide is listed as a probable human carcinogen by the EPA.

Chlormequat Chloride

Chlormequat chloride helps produce thicker stems and shorter plants. In effect, it slows down plant growth to encourage flowering. The resulting shorter bushier plants are much more adept for indoor growing. Although there is no evidence of carcinogenicity from chlormequat chloride, there are strong suspicions that it is harmful in large doses. Several documented cases of organ damage along with skin and eye irritation exist among people who were unlucky enough to ingest large amounts chlormequat chloride.

young woman smoking weed on the beachHow to Tell if it’s PGR Weed

Thankfully it’s quite easy to spot PGR weed. One giveaway is rock-hard buds. If unattractive brown hairs cover the bud surface and said buds emit little to no scent, this isn’t good. Odds on you’ve got your hands on some PGR weed.

One notable characteristic of PGR weed is the reduced presence of trichomes — the microscopic crystals that coat the leaves and buds. They act as the all-important resin glands where much of the medicinal benefits of the plant exist. Without them, those medicinal effects simply won’t manifest as strongly.

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One final feature of cannabis associated with PGRs are buds that feel spongey. The increased density of PGR weed means that the curing process doesn’t complete as it should. The result is a spongey brown bud with little to no scent that provides a poor smoke.

The Unintended Consequences of Black Market Cannabis

In places where cannabis remains illegal, or where testing is not yet up to speed, many patients can find themselves exposed to PGRs. As a result, many have lost the connection to what makes the quintessential cannabis experience.

It’s in everyone’s interest to ensure that cannabis companies don’t expose consumers to these compounds. Alongside the decreased medicinal benefits of PGR weed, this report from the National Resources Defense Council show many PGRs to be cancerous, toxic, and clearly not fit for human consumption. The only reason these exist is due to prohibition, a thriving black market, or the lack of enforced regulation in legal jurisdictions.

If someone attempts to sell you cannabis that a grower has clearly treated with PGRs, then it’s better to go without. Aside from severely compromised medicinal benefits and the above dangers there are other side effects. Many people report paranoia, scattered thoughts, and headaches after consuming PGR weed.

Coupled with a true intention to heal, the expertise we have across the globe in holistic cultivation methods means that there’s no reason for anyone to tolerate the presence of PGRs in their weed.

Author avatar

Francis Cassidy
Francis Cassidy is a freelance writer who writes on a variety of topics. With a particular focus on the cannabis industry, he aims to help ensure the smooth reintegration of cannabis back into global culture. When not writing, he's to be found exploring his new base in British Columbia, Canada. You can follow his other works including his photography on his blog


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    Mário Manuel

    I and I is giving many thanks and praises to have this knowledge shared keep good thanks for the time.

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    Peggy Darling

    I understand about the importance of less chemicals in medicine. One of the reasons cannabis was legalized. I live in Oregon. Before recreational, I could buy quality medicine and be sired it was detrimental to my health. Now, there is so much bad cannabis in the dispensaries that I have to go to the black market again to get quality organic medicine. Now, that marijuana grown with chemicals is concentrated into oils and smoked people are smoking these chemicals in high doses in the oil. Maybe, one of the reasons for the current problems, especially with the e-cigarettes. Another way of telling is that if the pot doesn’t smoke up in the bowl and one is left with half a bowl of black crap then that is the chemicals and shouldn’t be smoked at all. So that means that one now pays inflated prices in the dispensaries for smoke where half of it is not useable. Greedy growers have been around forever. Anyone needing true medicine has to go back to the black market. It is sad, but hey, I grew weed before legalization and known how truly organic cannabis can be grown. Even then the growth enhancers were organic, but had to be washed out real well or the pot would taste like fish fertilizer. Insist on organic weed!!!!!!!!!

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    Full, hard sense bud is grown everyday all day without PGRs. Scaring a consumer into believing a tight well maicured bud without trics on it is evil or dangerous is careless. More than times than not if a nicely grown flower lacks trics it’s because the grower tumbled it to keep the kief. Also, there’s plenty of organic PGRs that aren’t bad for the bud nor the consumer. Thank you for bringing this topic to light, but ask a professional about it before making circulating information.

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    John smith

    Liquid seaweed and kelp are examples of pgr’s. Nothing scary or harmful there. This is mostly misinformation which in the end can cause more damage and is extremely dangerous when presenting something less than accurate as fact

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    John smith

    Dense bud has more to do with the cultivar, lighting and understanding of phosphorus uptake than the addition of additives

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    Randall Anthony Hill

    Very informative. Thank you for that.

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    I don’t understand the people who are trying to defend the use which normally means they are lying.
    This is 2021 and things have gotten out of hand, nearly all bud gets found out by my rosin press. I am going to give up until I find a reliable source, these people are robbing smokers.

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