What Are Synthetic PGR's And Their Dangers

Are synthetic plant growth regulators bad for you?
15 December 2020
6 min read
What Are Synthetic PGRs And Their Dangers

  • 1. Why are synthetic pgr's used?
  • 2. What are pgr’s?
  • 2. a. Auxins
  • 2. b. Gibberellins
  • 2. c. Cytokinins
  • 2. d. Abscisic acid
  • 2. e. Ethylene
  • 3. How are pgr’s used in cannabis?
  • 3. a. How pgr’s affect cannabis?
  • 4. Are pgr’s dangerous to humans?
  • 4. a. The dangers of pgr’s to the environment
  • 5. Are there natural pgr’s?
  • 6. Signs of pgr-grown buds
  • 7. In conclusion

If you’re a cannabis consumer it’s likely that at some point you’ve seen buds that looked like a rock and had an odd brown or orange color, if you’ve seen something like this, it’s likely that they were grown using PGR’s. Synthetic PGR’s are human-made hormones used to promote denser flowers and make plants develop short and bushy.

1. Why Are Synthetic PGR's Used?

So, most home growers won’t even want to get near PGR’s because they want to smoke the best bud possible but with some commercial growers, the story is completely different.

As you may know, some strains are naturally denser than others, for example, Indica strains usually produce denser buds than Sativas so commercial growers must adapt their growing conditions to that specific cultivar but when growing commercially, this can be a bit hard and time consuming so basically, the major factor for PGR use is increasing profits and having more product for sale in less time as possible.


What are synthetic pgrs: why are they used?

PGR's are mostly used by commercial growers who want to get better yields faster.

As said above, PGR’s can increase bud density and shorten the life cycle so as cannabis becomes a big business, commercial growers try to increase yields per harvest and shorten growth cycles, obviously, not all growers use PGR’s but the competitive market tempts some growers to manipulate their plants to help save costs and maximize yields.


2. What are PGR’s?

Plant growth regulators (PGR’s) are man-made chemicals used to manipulate plant growth, increase branching, suppressing growth, and altering the flowers appearance.

There are a lot of PGR's that are basically grouped into five types, how well they work depends on various factors such as plant vigor, plant age, cultivar, and weather, these five types are:


Auxins promote growth and can contribute to the elongation of stems but in high doses can inhibit the growth of lower buds.


What are synthetic pgrs: what are they?

the appearance of a PGR-grown bud.


Gibberellins promote stem growth, elongation, being used to improve the size of the buds and also used to delay ripening and improve density.


Cytokinins promote branching and stimulate flowering, promoting plants to grow more branches and flowering earlier, resulting in denser buds.

Abscisic Acid

Abscisic Acid inhibits stem growth and helps regulate water loss from cannabis plants.


Ethylene promotes the natural detachments of leaves and fruits, also inhibits stem elongation, and can lengthen storage life.

3. How Are PGR’s used in cannabis?

PGR’s can be used to modify most plants and are usually used to alter apple trees, strawberries, and cherries, for example, in cannabis plants, plant growth regulators and used to modify the appearance of the buds, increase yields and make the plant more uniform to better fit in indoor grow spaces.


Most common PGR's in Cannabis

Active ingredientFunctions
AncymidolGrowth inhibitor
Gibberellic acidIncrease fruit production
CytokininEnhance color and growth
Chlormequat chlorideInhibits stem growth
PaclobutrazolPromotes uniform flowering and reduces internodal space.


Some growers also claim that PGR’s can make cannabis plants grow healthier, stronger, and more resistant to diseases but this may not be true and most likely a lie to make cannabis consumers buy PGR grown buds and increase their profit.

How PGR’s Affect Cannabis? 

So, now you know that plant growth regulators can increase yields and manipulate growth, but how do they work?

Manipulate Growth Cycles

Plants use signals that allow them to respond to environmental and chemical changes, this signal pathway works in sequences of biochemical reactions, so for example, this way a cell can generate a response to a stimulus.

This stimulus consists of a receptor, and a pathway where the stimulus travels through, so when the receptor receives the stimulus, the plant will develop according to the stimulus. 


What are synthetic pgrs: how are they used?

Growers can control yields and a plant's structure when using PGR's.

Now, PGR’s will repress this stimulus, obviously, this can vary from one specific plant growth regulator to another but in general, they repress these stimuli and allow the plant to continue creating growth-stimulating genes or stop producing them.

This can also be used to manipulate the flowering stage, for example, by using these chemicals, you can induce flowering earlier or even turn off the genes responsible for plant growth to keep your cannabis plants short and stocky, which can be useful for growers who want to maximize their growing space.

Increase Yields

Just like when manipulating plant growth and growth cycles, plant growth regulators can increase yields by activating specific genes that make cells expand. As these cells are activated, they will expand and be able to absorb more water which ends up in heavier buds.


What are synthetic pgrs: how are they used?

PGR's can be used to get denser buds, although denser doesn't mean more cannabinoids.

But this cell expansion comes with a downside because the extra weight is mainly made out of water and cellulose, and while the buds get bigger and denser, the trichomes production will stay the same so when comparing a regular bud with a PGR bud, you’ll get a lower cannabinoid content.


4. Are PGR’s Dangerous To Humans?

Not all synthetic PGR’s are extremely dangerous but yes, they are bad for your health. High doses of synthetic plant growth regulators can be dangerous in the short and long term.

For example, in the 80’s, there was a recall of foods that tested positive for Daminozide as it was suspected that it could be a carcinogen, and since 1989 a lot of PGR’s have been banned from human consumption as further tests have been concluded.

Another bad plant growth regulators is Paclobutrazol which has been proven that can cause liver damage and affect fertility in men and women, several others are still being tested, but in general, it’s not good to consume them.


What are synthetic pgrs: are they dangerous?

PGR's can be harmful to humans if consumed in high quantities.

Unfortunately, PGR’s in the cannabis industry is not as regulated as in the agriculture industry, for example, this happens because cannabis is not legal everywhere so the regulations and quality may differ.

Now, obviously, you won’t die by smoking a joint of PGR bud but it’s always to be safe and avoid this type of chemicals because, over long periods of time, it can harm you.

The Dangers of PGR’s to the environment 

As well as being potentially dangerous to humans, PGR’s are also environmental pollutants because when growing with plant growth regulators, there can be residual PGR’s left in the soil and water, and it has been shown to have toxic effects on animals and as they’re used incorrectly, can affect microorganism diversity of the region due to soil runoff and infiltration in lakes or ponds.  

So, in general, you can use PGR’s safely if used properly but if you use the wrong type, in improper concentrations, improper equipment, or incorrect application, it can end up poisoning animals, humans, and plants.

5. Are There Natural PGR’s?

Now that you know what PGR’s are and their dangers, you should also know that there are natural PGR’s and it can be quite easy to get them, so if you want to have similar effects without the dangerous effects, here are the most common ones.


What are synthetic pgrs: natural pgrs

Have in mind that synthetic PGR's are dangerous but natural plant growth regulators are not.


Chitosan is derived from chitin which is a molecule found in the exoskeleton of crustaceans, these organic molecules can be applied as a foliar spray and as a soil drench.

When used properly, it will target a plant’s cell nucleus and plasma membrane which can end up increasing photosynthesis, boost plant growth, and increase nutrient absorption.

Also, chitosan has strong anti-disease benefits that can increase a plant’s defense against pathogens and increase terpene production in most plant species.


Triacontanol can be found in a lot of natural resources such as alfalfa meal, sugarcane, and beeswax, this fatty alcohol is non-toxic and studies have shown it to be a growth stimulant which can affect photosynthesis, enzyme activity, nutrient absorption, and CO2 assimilation.


6. Signs of PGR-grown buds

To be 100% safe that you’re not smoking PGR buds, here are a couple of images to help you identify them, as you will see, they are quite different but it’s not impossible to get confused.

As you may see in the image below, PGR-grown bud is quite similar to regular cannabis but there are basically 2 things that you should have in mind:

  • Bud appearance
  • Pistil quantity

In this photo, you can see that both buds look basically the same but the one on the right (grown with PGR) has more brown pistils.

What are synthetic pgrs: differences

Basic differences of regular-grown and PGR-grown buds.

Also, if you go to your local dispensary and see buds that look very homogeneous, they may be grown with PGR’s, as you can see, the same buds grown with and without PGR’s have completely different appearances, and although the one on the left may look like it’s less strong, the one grown with PGR’s would usually be less potent.

7. In Conclusion

PGR’s won’t harm you if you smoke it once or twice but it’s always better to be safe than sorry so here are our tips to avoid PGR-grown cannabis.

If you have experience with plant growth regulators, please share your knowledge with fellow growers, leave a comment in the comment section below!



  1. Plant growth regulation.  - Haas, Ulrich & Harp, Tyler. (2015). 
  2. Plant Growth Regulators. - Basuchaudhuri, Pranab. (2020).  
15 December 2020