What Are Plant Growth Regulators (PGR)?

PGR Flowers

When it comes to flower, most people focus on potency, flavour, or terpene profile, but there’s one factor that’s just as important (and often overlooked): how flower is grown.

If you’ve ever heard the term “PGR flower,” you’ve already brushed up against one of the most concerning topics in cannabis cultivation today, Plant Growth Regulators (PGRs). These synthetic chemicals are used to manipulate plant growth, but they come with serious consequences for quality, safety, and even your health.

What are PGRs?

Plant Growth Regulators (PGRs) are synthetic or natural substances that control how plants grow and develop. In agriculture, they’re used to boost yields, control height, or speed up flowering.

PGRs are often misused to make flower appear denser, heavier, or more visually appealing, creating the illusion of high-quality product.

Common synthetic PGRs found in cannabis cultivation include:

Paclobutrazol

Slows growth and increases density, but can reduce cannabinoid and terpene production.

Daminozide (Alar)

Once used in fruit farming but banned for human consumption due to carcinogenic risks.

Chlormequat chloride

Used to control plant size, with evidence of potential toxicity.

What's the problem?

Reduced Cannabinoid and Terpene Content

PGR-grown flower often looks great but lacks potency, aroma, and flavour. That’s because these chemicals interfere with natural cannabinoid and terpene development, the compounds responsible for effects, smell, and therapeutic value.

Health Risks

When combusted or vaporised, synthetic PGRs can produce toxic residues that may irritate the lungs or, with long-term exposure, pose more serious risks. Some of these chemicals were banned from the food industry decades ago, yet still appear in unregulated markets.

Environmental Impact

Synthetic PGRs can leach into soil and waterways, harming microorganisms, insects, and surrounding ecosystems. In short, they’re not just bad for you, they’re bad for the planet.

How to Spot PGR

It’s not always obvious, but there are a few telltale signs that cannabis may have been grown with PGRs:

– Buds are unusually dense or rock-hard (almost sponge-like).

– Colour appears brownish or dull, with less trichome sparkle.

– The smell is faint or chemical-like, instead of aromatic and earthy.

– Harsh smoke or unusual residue when burned.

When in doubt, trust your senses.