Education Resources

PGR: The Toxic Chemicals in Your Marijuana

Written by mitch

Greetings, FABulous people! Let’s talk about PGR.

Has it ever occurred to you that the weed you’re smoking may actually be packed full of toxic chemicals?

Don’t believe me? It’s more common than you may think. Plant Growth Regulators (PGR’s) have flooded the black market in recent years. It’s gotten so severe that many Australians are losing touch with what an authentic cannabis experience actually feels like. This is particularly true for the younger generation, who are beginning to use marijuana for the first time.

What are PGRs?

Are your buds rock hard? Perhaps they’re covered in ugly, brown hairs? Maybe the buds themselves don’t have much of a smell to them? If this sounds familiar to you, it’s likely that you are smoking weed that has been treated with Plant Growth Regulators.

So, is PGR weed bad? The answer is a resounding YES. PGR’s are typically used to fatten buds up, so they weigh more. This (of course) benefits those who currently profit from the growing and sale of cannabis. However, PGR has some adverse health effects, and long term use can prove highly detrimental.

The most common PGR’s are Paclobutrazol (PBZ), Daminozide (a.k.a. Alar), and Chlormequat Chloride. In this article, we are going to focus on Paclobutrazol, the most common PGR used in Australia.


PBZ is a plant growth retardant which works as a gibberellic acid antagonist. In effect, this means that it binds to certain enzymes that are crucial to the cannabis growing process. Paclobutrazol inhibits the terpene synthase enzyme, causing a bottleneck in the terpene synthesis pathway and the THC synthase pathway.

Paclobutrazol significantly reduces (but does not completely halt) a hemp plant’s capacity to produce THC, the primary psychoactive compound in cannabis which actually helps you get high. PBZ also reduces the plant’s ability to produce terpenes, the chemicals that produce the dank smell of cannabis. PGR weed is not only less appetising than usual, it’s also usually lacking the potency of other buds.

Ultimately, Paclobutrazol causes the plant cells to divide, rather than elongate. As a result, the cells are packed closer together, with the flowers accommodating less space between calyx’s/pistols. Buds treated with PBZ are often rock hard and covered in thick, entangled hairs. It is important to remember that density alone is not necessarily an assurance that the bud contains Plant Growth Regulators since some strains are naturally quite dense.

Combustion of Paclobutrazol (as when smoked) causes the compound to break down into nitrosamines, the most carcinogenic component in cigarettes. It’s found to make liver cells swell up, causing direct damage to your liver.[1][2]  Paclobutrazol will also make it harder for any young buck to impregnate women, as it wreaks havoc on human sperm count. For those of you who don’t want kids and don’t really mind poisoning your body, well…. [3]

A Persasive Problem

The ubiquity of PGR weed is pretty terrifying. If you’re sitting there wondering whether the weed you have been smoking is PGR or not, the answer is most likely yes. Particularly if you’re smoking hydro in any major Australian city, there’s a solid chance that you have unknowingly been consuming PGR grown cannabis. Its use is mostly pushed by the Australian crime syndicates, which control a significant portion of the black market.

When trying to identify PGR, we typically look for rock hard buds covered in brown hairs, with a lack of any visible trichomes (the ‘pollen’ of cannabis). Often the weed feels “spongey” – this is because its density negatively affected the drying process. There is also often very little smell. If your weed ain’t stanky, it’s a sign that something is wrong!

Spot the PGR!

Here are a few pointers to help you identify PGR grown weed:

This image is quite standard for Australian PGR weed. There is a darkness and dullness to the buds; the hairs are brown and dense. There are basically no visible trichomes. It honestly just looks incredibly ugly. Terrible smoke.

The image below, on the other hand, has a few PGR-like characteristics. It has a lot of orange hairs, for instance.  However, trichomes are visible all over the weed when you look closely. Additionally, the buds are not all that dense. This is an example of some high quality weed.

The image below has an example of PGR put directly next to non-PGR cannabis. Quite easy to tell don’t you think?

I want to apologise for this next picture because it is utterly revolting – hell, it makes me wanna vomit. The smell of ammonia instantly comes to mind when looking at it. Covered in ugly brown hairs and dominated by thick stems, anything that looks like this is sure to be PGR. To top it off, the white, yellow and black powder growing on the buds in this photo is actually mould.

After that pitiful excuse of a bud, let’s try to finish on a positive note. Here we have another specimen with a heavy concentration of brown hairs. The weed is quite dense, but those trichomes are quite obviously visible. A beautiful example of good weed right here.


Here’s the Rub

PGR’s are toxic, cancerous and highly dangerous for human consumption. The only reason Plant Growth Regulators are so prevalent is the complete lack of regulation over black markets from the Australian Government.

The amount of frequent cannabis users keeps increasing year after year, making PGR buds a greater health risk to regular citizens. According to the 2016 National Drug Strategy Household Survey (NDSHS), 34.8% of all Australians have tried cannabis, with 10.4% having consumed the drug in the past year. Our prohibitive laws have struggled to keep up with the pace of the black market, which has proven it can turn a profit, irregardless of its legal standing.

If this issue is important to you, please be sure to write to your local members of parliament. Help inform them of the true public health dangers of cannabis prohibition. An unregulated black market full of PGR buds will continue to endanger the health and wellbeing of regular Australians.[4] Furthermore, please say ‘NO’ to PGR weed. If somebody sells you some shitty looking cannabis, decline it. It’s better go without that poison in your body than subject yourself to a crappy, scattered and paranoid high, complete with a headache. Finally, help spread the word about PGR weed by sharing this article and/or telling your friends.

F.A.B is considering the possibility of a “Is this PGR” segment in future, where users would be able to submit photos of their buds and receive a quick response, either from the F.A.B moderators or other members of the community, as to whether it’s PGR or not. Let us know in the comments if like the idea of such a feature.

Works Cited:

[1] Commonwealth of Massachusetts (MDAR): Paclobutrazol, January 2012 –

[2] California Environmental Protection Agency: PACLOBUTRAZOL, January 1993 –

[3] PubMed: Exposure to Paclobutrazol disrupts Spermatogenesis in male Sebastiscus marmoratus, October 2015 –

[4] AIHW: Illicit use of drugs, January 2018 –

Finally, a big thank you to the /r/ausents community for the photos of PGR weed and /u/heavydayzecollective for his write up on PGR.

About the author


Mitch Keys is a young writer from Brisbane, Australia unfolding in a dynamic process of becoming (like everyone else, so don’t go thinking he’s special or anything). He likes being alive.

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RJ Thomson
RJ Thomson

Thanks for the info….A big help….. Forewarned is forearmed


It’s always preferred to only work with the best growers in your area. People adding unnecessary things to your marijuana is something you want to avoid as much as you can.

Joe LaGrasso

It’s hard in Australia, it’s a very closed off community because it is still so very illegal here.


Hey Mitchio,
I often struggle getting good quality buds which has set me on a path of looking to cultivate my own good quality fluffy trichome frosted buds.


[…] experience in Brisbane, where he has observed that some people are quite keen on handing off PGR buds (Plant Growth Regulators). Experiences between the two are often night and day, as is the quality of the high. It’s always […]


[…] (First: Maybe it’s worth checking that your buds weren’t sprayed with Plant Growth Regulators… Don’t know what to look for? Check out our article on PGR weed here).[2] […]


I’ve been saying for months there’s something not right with the buds we get….. I always referred to it as being chewy…. Doesn’t fluff when you cut it sometimes has smell but rarely… This arrival has confirmed my fears…. We can’t get onto anything else… Got my plants in but months before they will help… What’s a person to do… It sux

Joe LaGrasso

I always called them “spongey”. And yeah it’s awful. Not much else you can do other than try and ask around unfortunately.


great article, well researched and written well

Joe LaGrasso

Appreciate the feedback!



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