Plant Growth Regulators (PGR) in Weed: Cancer-Causing Marijuana

While many people enjoy smoking and vaping marijuana, only a few healthy, conscious cannabis consumers know where or how the herbs are produced. Before using any marijuana herbs, it is essential to ask vital questions such as who grows the weed? How was it grown?

Did the grower use chemical fertilizers or was it grown naturally? And most importantly, was the weed exposed to harmful Plant Growth Regulators (PGRs)?

In this article, we will explore PGRs in weeds, how to identify them, their side effects, and their potential dangers to our health. This article may encourage you to start growing your own cannabis. We’ll also try to make this piece as simple as possible without scientific jargon.

pgr difference

What are Plant Growth Regulators (PGR)?

Plant Growth Regulators (PGRs) are chemicals or substances used to alter the natural behaviors of crops through physiological actions. PGRs are used to manipulate the growth cycles of plants by slowing or speeding their maturation rate mostly for quicker harvests and commercial benefits.

These substances are also called Plant Growths Regulators (Retardents). They are used on edible plants such as peppers, tomatoes, etc., to control their maturity, fruits production, and storage capacity.

Plant Hormone Classes

To clarify how PGRs work, we need to first understand the different classes of plant hormones. They’re a group of five special chemicals that play a major role in the growth and development of crops. It’s these hormones that PGR work on to alter the natural cycles of the plant.


Gibberellin has many roles to play in the development of crops. It’s this hormone that promotes the germination of seeds. It also helps the seed to start growing while producing photosynthetic leaves. Seedlings use Gibberellin for food storage and during vegetative growth, Gibberellins stimulate internodal spacing and stem elongation.


Auxin is next on the list. These hormones regulate the formation of the root, shoot, and fruits. Crops with a high level of auxins have plasticity in their cell walls, which helps to stretch outgrowing cells. The bigger the cells, the bigger the tissues. This in turn makes the organs bigger, and this helps to produce bigger fruits and beautiful flowers.

These hormones are also responsible for the way crops grow towards the light. This is known as phototropism and it makes the cannabis light cycles are very


This hormone is as vital as auxins. If the Cytokinin in a plant is 50%, auxin will be 50%, and if one is 60%, the other will be 40%. A lower level of Cytokinin combined with a higher level of auxin will help boost vegetative growth in the plant. On the other hand, a higher level of Cytokinin and a lower level of auxin will transit the crop into the flowering stage.

Higher levels of Cytokinin generally give plants shorter internodal spacings while making them grow bushier. They can be mistaken for growing indica plants but they are definitely shorter with less spacing. Both hormones are usually balanced in PGRs to induce how the weed grows.

difference between pgr and no pgr weed


Ethylene is a gaseous substance that is released as the pectin in the cell wall of a ripe or rotten fruit breaks down. Once the ethylene gas is released by one riped fruit. This triggers nearby fruits to ripe prematurely, which can lead to the rotting of the whole bunch.

Just like Auxins, this hormone also contributes to phototropism, including the initial development of the leaves and stem growth.

Abscisic Acid (ABA)

This hormone is known as Mother Nature’s timer. Abscisic Acid (ABA) is found in coats of developing seed, and when the seed falls, the gradual dissipation of the ABA helps to promote the seed dormancy.

Additionally, if the plant is experiencing water stress, the levels of ABA increase immediately and this helps to modify the concentration of sodium and potassium. This causes the stomata to close and water is saved.

Boost Marijuana Yields

Now that you have an understanding of plant hormones, the next big question is how do PGRs boost marijuana yields? A simple explanation: While some Plant Growth Regulators are used to alter the natural creation of plant hormones that prevent or retard plant growth, others are used to boost growth.

What this means is that weed growers can activate some genes in marijuana to boost the growth cycles. This way the weed forcefully enters another stage of growth than it is supposed to. Also, growers can decide to shut down certain genes to prevent the bushy growth of the plant. This is mostly used by those trying to maximize small growth space.

It is not surprising to see an increase in the use of these gene killers in growing weeds. Especially considering the stiff competition in the cannabis industry, every grower wants to make a profit. Using these regulators to boost marijuana yields has become a norm for many. But do they care about the potential dangers of PGRs on the health of the final consumers?

How to Identify if Your Weed has PGR

While it is one thing to purchase your marijuana from reputable dispensaries, it is another to know if your weed was treated with PGRs. So how do you identify if your marijuana was sprayed down with this? It is quite easy if you can take out time to observe the buds.

PGR weeds usually have ugly and rock-hard buds. The buds are dark and dull with dense brown hairs that make the weed unattractive and terrible to smoke.

pgr and without pgr cannabis

Side Effects of PGR Weed

The side effects of smoking PGR marijuana depend on the type of PGR used to treat the weed because it’s not every PGR that is actually bad for consumption. However, some of the major side effects of harmful PGR weeds include liver toxicity, liver damage, infertility in men, and irregular respiration.

Can You Get Cancer from Smoking Weed with PGR?

Some PGRs are cancerous. For instance, research in the 1970s showed that Alar scare, an artificial chemical for speeding the maturation rate of cherries and apples, contained compounds that caused cancerous tumors. They were generally in the blood vessels, lungs, and kidneys of laboratory animals when consumed severally at the maximum tolerated dose (MTD) for men.

In the late 1980s, Alar was banned in the US for use in the growing of food crops after it was classified as a “probable human carcinogen” by the Environmental Protection Agency (EPA).

Similarly, Paclobutrazol (PBZ), another popular PGR that works with enzymes in the growth of marijuana, is known to contain harmful compounds. PBZ hinders the development of terpenes, the organic compounds that give plants their unique taste and smell. This means that weeds that are treated with this chemical will have little or no fragrance.

When a weed treated with PBZ is combusted, it releases a compound that breaks down into nitrosamines. These are the most carcinogenic compounds found in cigarettes and can cause infertility and liver problems.

However, it is important to note that countries like Britain have approved PBZ for the growth of food crops such as apple, cherry, pear, apple, etc.

Final thoughts

While some PGRs are actually beneficial for growing certain crops, we recommend you stick to marijuana that was grown organically. This way you do not face any of the potential dangers of smoking PGR weeds.

Whenever you visit a dispensary, ensure that you observe the appearance of the herbs and always ask your budtender about the kind of PGR used to treat the weed.


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