What Are PGRs

Are you curious about what effect PGRs (plant growth regulators) have on humans, the environment, and Cannabis buds? Here we explore everything you need to know about PGRs so that you can make an informed decision on whether or not to use them.

Plant growth regulators (PGRs) are chemicals that enhance bud size and yield by interfering with plant hormones to encourage processes associated with growth, while inhibiting the ones that prevent it. Unfortunately, PGRs can harm the environment and might be dangerous for people too. To learn more about these debatable growth boosters–including how to identify weeds related to them–read on.

What Are PGRs in Weed?

Plant growth regulators (PGRs) are chemicals that help to control plant growth and development. Some of these chemicals occur naturally in plants, where they play an important role in driving different physiological processes. However, humans have also developed synthetic PGRs that can be applied to crops to increase yields and extend the post-harvest life and storage quality of fruits.

Commercial cannabis growers have taken notice of these chemicals for obvious reasons. If they work well on other crops, then it’s logical to assume that plant growth regulators could help increase bud size and yield, resulting in more profit. But are PGRs safe for consumers?

Alarmingly high levels of pesticides and herbicides have been found in cannabis smoke by studies that assess for pesticide residues. This contamination is significantly concerning to researchers who describe it as “alarmingly high.” Scientists are now starting to explore the phenomenon of PGR residue in buds.

Many people are looking for organic, sustainable, and artisan cannabis products that don’t contain synthetic chemicals and are grown on a smaller scale. Some research suggests that water pipes and bongs help to filter out some nasty chemicals, but the presence of any contaminants doesn’t sit well with many cannabis users.

PGRs, or plant growth regulators, are often used on food crops to improve the shapes of fruits and vegetables or to prevent them from dropping prematurely. However, many commercially grown foods also contain pesticide residues which can be dangerous if ingested. Just because an agricultural input increases growth and productivity doesn’t mean it is safe for human consumption.

Learn everything there is to know about plant growth regulators (PGRs) below, including how they work in plants, if they are harmful, and how to identify weed grown with PGRs.

The Role of PGRs in Plants

Plant growth regulators (PGRs) are plant hormones that help to regulate processes such as growth, flowering and fruiting. In animals, hormones circulate in the body to exert their effects on distant organs and glands. However, in plants, hormone substances tend to produce their effects right where they are synthesized. This means that these chemicals can create isolated effects – but they also work together to produce a range of responses.

The main PGRs found naturally in plants include:

Abscisic acid

The PGR mentioned functions by closing stomata (tiny pores on leaves’ surface) during droughts. Stomata ordinarily regulate the gases that enter and exit leaves; however, by closing them, plants are able to conserve water when it becomes scarce. Furthermore, abscisic acid is also responsible for abscission—the natural detachment of dead leaves and fruits from branches.


The plant hormone ethylene is responsible for the senescence of leaves and flowers. For example, have you ever picked a tomato and watched it turn red on the windowsill? This process is accelerated by ethylene’s ripening action off the branch.


This chemical, gibberellin, is key for germination. When germination begins, enzymes active gibberellin which then breaks the seed’s dormancy. The molecule also regulates sexual expression and plays a role in hermaphroditism in numerous species. Additionally, auxin is a plant growth regulator (PGR) that performs several crucial roles such as formation of root cells. Auxins also underpin phototropism—the process that causes plants to grow towards light—making it vital for plant development..


These chemicals work to fight off senescence and promote cell division.

Why Do Growers Use PGRs on Cannabis?

Although they may be appealing to the eye, these cultivators use Plant Growth Regulators (PGRs) to achieve bigger and thicker buds, but this comes at a price.

PGRs work by ‘hacking’ the plant’s natural hormones. These naturally-occurring hormones maintain control over breakdown or activation of transcription proteins, which either promote growth by activating genes, or prevent growth by suppressing them. However, when synthetic exogenous hormones are introduced, they disrupt this process. By adding Growth Hormones that activate target transcription proteins growers achieve two results: an increase in number of proteins that promote growth, and suppression of those that normally put on the brakes.

The result of this tweaking creates bigger, more robust buds that are much more visually appealing. The activation of genes promoting growth leads cells to absorb greater amounts of water, causing them to expand. Auxin also assists in enlarging plant cell walls.

However, despite bigger buds, playing around with plant hormones comes with a serious downside to cannabis growers; compared to normal flowers, PGR weed features lower levels of cannabinoids and terpenes. As such, these buds are much less tasty than those that don’t undergo treatment and produce little-to-no psychoactive effects.

Are PGRs Dangerous?

The harmful effects of PGRs, or potentially hazardous chemicals, are coming under greater scrutiny. Some countries allow farmers to use daminozide as a pesticide; however, Europe considers it a carcinogen and has made its agricultural usage illegal.

Explore the most common synthetic plant growth regulators, and the risks they may pose:

Chlormequat chloride

Although this molecule is helpful for plant growth, exposure to it can cause lung irritation and nausea. If a person is exposed to this chemical over long periods of time, they may experience liver damage.


Daminozide, known as Alar in the United States, is a plant growth regulator (PGR) used on fruit trees. According to the Pesticide Properties DataBase published by University of Hertfordshire, it is listed as a probable human carcinogen.


This chemical works to supress plant growth. It does this by inhibiting the natural PGR gibberellin, which then helps reduce internodal spacing and creates stouter plants that fruit earlier. Though, the molecule has been shown to produce issues with reproduction and development in animal models.

How PGRs Impact the Environment

Not only do PGRs have the potential to threaten cannabis consumers, but their industrial-scale application also means they end up polluting the environment.

If soil isn’t cared for properly, it erodes and runoff increases, causing chemicals topollute groundwater, rivers, and the wider ecosystem. The consequences of this pollution are largely unknown, although some studies show that PGRs can disturb organ development in certain species of fish and inflict damage on animal reproductive systems.

How to Identify PGR Weed

PGR weed is unfortunately prevalent these days, especially in areas where cannabis isn’t Federally regulated. So, how can you distinguish between PGR treated and untreated buds? paying close attention to certain key characteristics; but before we get into that, it’s important to understand that not all growth regulators are toxic. In fact,, some natural ones like kelp and chitosan yield similar results as synthetic treatments- without the adverse health effects. With this said, when examining potential purchases, be sure to consider your source and level of trustworthiness: Are they reliable? Have you bought from them before? When in doubt, err on the side of caution.

  • Dense buds: PGR weed is extremely dense. Although some growers take pride in how dense their flowers are, PGR buds look unnaturally thick due to the unnatural hormone hacking they undergo.. They feel heavier in the hand, and they’re slightly harder to break apart with the fingers.
  • Reduced aroma: Terpene profiles are negatively affected by PGRs, resulting in larger but less aromatic flowers. In fact, these thick blooms barely smell of earthiness when held close to the nose.
  • Dark colouration: The PGR weed is much darker in color, almost brown. Because it has less trichome count, the sparkly glands that produce cannabinoids and terpenes are reduced, giving it less of a sheen.

PGRs: A Reason to Grow Your Own or Shop Wisely

With the proliferation of weed, a lot of it is laced with PGRs. However, this doesn’t need to be seen in a negative light. While Smoking PGR-laced weed isn’t something we recommend due to a lack of safety data, these contaminants make users think twice before buying cannabis. This could lead them toward growing organically at home or purchasing naturally cultivated buds from small businesses in legal markets–which would ultimately be better for everyone involved.

The more we educate ourselves about the potential dangers of chemicals used in cannabis cultivation, the better equipped we are to make informed decisions.

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