Let's talk PGR's

PGRs (short for Plant Growth Regulators) are a dirty not-so-little-secret in cannabis cultivation. Many – most – PGR’s are banned for human consumption, but still they are often discovered in regulated markets through mandatory lab testing and in places where there isn’t market regulation (take Arizona, for instance) it’s up to the consumer to hope for the best.

The PGR that got the worst reputation and has been mostly blacklisted in the cannabis industry is paclobutrazol. If you’ve been smoking herb for long enough, chances are you have put some paclobutrazol in your body. You can spot buds grown with paclobutrazol because they will be rock-hard – like breaking the teeth on your grinder hard. That bud density increases overall weight, which increases the profit margins for the grower. Unfortunately, unwary consumers are the one who pay the ultimate price for the growers’ unethical behavior.

The fact is, these PGR’s are carcinogenic and are linked to some pretty bad physical consequences. PGR’s are not labeled for human consumption, but unscrupulous growers all over still use them…some growers don’t even know they are using PGR’s since many PGR’s are unlabeled ingredients in popular nutrient formulations – Snowstorm, Superthrive, Gravity, G10, and Fire from Heavy 16 all contain the PGR triacontanol.

This may not be the most comfortable topic, but I want to hear about folks’ experiences with PGRs. Have you used them? When did you quit using PGR’s? Is this the first time you have heard about PGR’s? @growopowners, @mastergrowers, @GrowOpEmployees, @LabOwner, @LabEmployees and really the whole @memberdirectory can chime in here. This is a topic that really affects our whole industry.


I am not familiar with triacontanol, but I can’t believe the EPA hasn’t cracked down on it. As a manufacturer myself, I am aware that they can be merciless with fines. Regardless of regulation, the thing that concerns me is manufacturers continuing to use materials that they must know are hazardous to human health. This is the dark side of the industry! IMHO if the cannabis industry wants to flourish, it must support lab testing to assure we are providing a wholesome product that consumers can confidently buy and enjoy. We definitely do not need a major public health issue coming to the forefront of the news cycle…


I agree, @TheMadFlascher. I think we are entering an era where regulatory testing will become commonplace. I think part of the issue is the lack of awareness in the industry (case in point the triacontanol in this example) Would you agree, @TheMadFlascher?


Early on I was told NOT to use Superthrive because it supposedly caused hermis. So I never did. Since then I’ve focused on organic growing and basically have stayed away from as many commercial inputs as possible. On the other hand, growing in a commercial setting there is more of a push toward quantity over quality, and I think that is a more vulnerable place to be in. We don’t use PGR’s in our commercial grow, but I can see how the temptation would be greater there than in growing for oneself. Indeed, more regulation is better for the industry. Citizens don’t seem to be very inclined to ask for test results, and financial gain is the main focus of most businesses. A third party, regulatory system, seems to be the only solution. Other than that - grow your own & grow organic :smile:


Cheers to that!


Nick, I would love to give them the benefit of the doubt! But honestly, as a manufacturer I don’t put anything is my formulations accidentally! If you are purchasing components, you must have some idea of whom is selling it and why I want to include it in my mix…I guess you can feign ignorance as an excuse, but I figure if I bought it and I decide to use it in my formulation…I OWN IT !!!


you’re 100% right, that’s the dark side of the industry.

While I do believe a lot of PGRs, like triacontanol, are probably very safe to use, I find it is unfair market practice and dishonest for consumers to hide these products within what is sold as a “fertilizer”.

I believe in free choice, if you want to use them and figure out for yourself , on yourself if they are toxic… Be my guest. When it comes to their presence on the market, I’m still surprised of how easy it is for so many company to have a bunch of different products, with obvious PGR effects on the plants, but only list “magnesium sulfate” on the label (or any other common thing that for sure doesn’t change morphology of plants one their own) and not get caught.

However, because the regulatory bodies in north America are very slow to reach the 20th century, a lot of growers are not able to access products readily available, now, in the 21 st century. These regulatory agencies also have very expensive and very difficult protocols to engage for small enterprises to bring those discoveries to market; as all those regulations are pretty much dictated by AgroChem giants that have their own way of doing things and would rather see those discoveries die off until they can themselves own it.

personally , I find Daminozide/Paclo Buds to look unnatural, taste bad and have about no effect… SO I’d rather growers learn to grow than resort to this kind of product, because I travel a lot and can’t always have trusted supply. :wink:

When it comes to Superthrive…didn’t we win world war II because of it or something? It has to be good !!
(only the old ones here, that have seen the original packaging, will know what I’m talking about here LOL)




@ericb, if I could like a post twice I would’ve liked yours thrice!

When I think of Victory in Europe or the Pacific during the War, Superthrive always springs to mind. Everyone here probably has a bottle of Superthrive lurking somewhere in the depths of our weird uncle’s garden shed :wink:

Very eloquent and specific response! I personally could not agree more! Thank you



So much depends on the regulatory jurisdiction! I am registered in Cali and ALL OF OUR REGISTERED LABELS are subject to testing. We also have a derivation clause on each label where we must state what our fertilizer is comprised of, and provide heavy metals lab analysis along with the label to the state.

The good thing is that any PGR’s stick out like a sore thumb when run through gas chromatography!

It is crazy though, I have seen some fertilizers coming from some states loaded with heavy metals…(giving the CDFA credit, they are quickly banned in Cali and we seldom see them show up here) FWIW

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The Superthrive guy was the nicest man- he was always at nursery trades shows, hawking his wares and giving away samples. I think they even claimed they could bring a 99 percent dead plant back to life- not to mention the pictures of petrified forests that were now lush. I haven’t thought about SuperThrive in a decade or better. Thanks for the humorous memories

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For the record: I wholly support the Superthrive guy and all his marketing efforts…just don’t put it in our herb! Save the trees :evergreen_tree:

I would love to keep the nostalgia alive: does anybody have pics of/with the Superthrive guy?


Thanks for bringing this up @Growernick. I’m still seeing flower in the LA area that definitely has been PGR’d but doen’t smell like phospho-load which was quite typical until banned. As the market gets educated about this health issue they will inevitably steer away from such product just like they did with the whole organic food movement.

Based on what I’ve seen, if you aren’t doing at least 2.5 lbs/light the problem isn’t because you aren’t using PGRs. If you are maxing out at 2.5, then rather than go with PGRs I suggest you tune your genetics, feed system and formula along with tightening up everywhere else until you hit 3+. If you want a premium price for your flower, that is.

At the end of the day, those who tarnish their reputation with PGRs in a largely health-driven market are likely to come up short on both ends - reduced demand and reduced sale price. Not a good business plan.


I wish this was the case about growers in MI. I’ve gotten so many notices via email and ig about failed tested bud. I’ve met so many growers out here that chops early, use pgrs, and etc per the dispensaries order to sell more bud. They won’t stop until someone gets sick and sues a company, grower, or dispensary. Heavy 16 is not that secretive about what’s in their stuff, and I know two licensed growers buying the stuff by the tote.


Until we see the day where the market has NO flower that has been PGR’d we have a duty to inform. Do you feel there are many consumers out there who just don’t know any better? It’s those folks we need to reach so they are educated consumers and refuse to buy flower that has clearly had PGR treatments.


Often we hear that PGRs increase yield beyond what is possible without, but I beg to differ.

maybe it helps bad growers with aweful grow conditions reach higher scores… but people have to keep in mind that 96% of dry weight is C, O and H (45%C, 45%O, 6%H) CO2 and Water.

therefore having proper climate and growers that wake up in the morning and water properly…

Paclo, Daminozide, Triac, IBA, NAA etc… will all affect the plants, mainly in a morphologic way, but really wont make the plant absorb more CO2 than the climate allows, neither will it provide water to plants forgotten by the sleepy grower…



No only is it in the buds but any runoff into watershed areas effect our drinking water. Our soil inoculate, Soil Balance Pro, is OMRI certified organic.


Scary stuff! I recall when we found trace amounts of SSRI’s and MAOI’s (anti depressants) in groundwater tables about 15 years ago…that sure changed the method of how we dispose of medications in group homes (i.e. no more two-man toilet drops)!

Have you seen any studies of PGR’s making their way into watersheds or into groundwater supplies?


I have not, but at last years Annual Horticultural event at the JW Marriott, an EPA employee brought up this concern during a Q & A after a PGR talk.


I believe Kelp and Alfalfa have PGRs in them naturally. I read that snowstrom /purple max is just a concentrated form of triacontanol extracted from alfalfa meal. The concentration and method of extraction may not be organic, but I’m not seeing the difference between someone using a product like that or just using alfalfa meal.
Fortunately I don’t have to worry about it since we are strictly organic. I spend time researching products that my supply shop tries to push on me if they are OMRI listed, but I still try to follow up and make sure we are not putting crap in or on our plants.


Working in the water treatment industry I see a lot of water analysis, both city and well water. After 15 years I am still able to be surprised to see what is in our water. The EPA “regulates” as much as they can, but there are contaminates that normally show N/D (non detected) are now being detected. Boron for example, it is showing up all over Michigan well water. Even though we need Boron in the water for grows, the levels that are showing up are catastrophic to plants and harmful to humans. I have a customer that even after RO treatment the Boron residual was still 0.07 mg/L. He couldn’t get the plants to take off for nothing. We had to polish the RO water with Mixed Bed DI Resin to pull it out. That is just one example. Flint Michigan is the perfect example that you can’t trust whats in the water even if you are on a city water. I can’t stress how important water test are especially when you doing a grow. If something shows up in your main source that can slip right through the RO, it can cause some serious headaches.