plant growth regulators weed

Synthetic PGRs are Dangerous… Are They in Your Weed?

When you see ultra-dense cannabis buds with an odd orange or dull brown coloring, they may have been treated with a synthetic PGR in the flowering stage. No good!

What’s wrong with these beautiful dense “hardball” buds? They were grown with synthetic PGRs.

Here’s a comparison of PGR-treated buds vs. naturally grown buds. It’s normal for weed to have orange hairs, but PGR-buds are often completely engulfed by them.

PGR is short for “plant growth regulator”. PGRs act kind of like hormones and, and some plants naturally produce PGRs. However, synthetic (human-made) PGRs were developed in the early 1900s to promote dense flowers and keep plants unnaturally short and bushy.

Two popular human-made PGRs are Paclobutrazol (Paclo) and Daminozide (also known as Alar).

Synthetic PGRs are still commonly used for grass on lawns (to keep it short) and ornamental plants (for uniform, weighty flowers), but many common synthetic PGRs were banned in the USA during the 1980s for use on any crops meant for human consumption.

Why? Because these systemic compounds remain in the plant tissue (regardless of flushing) and once consumed, there is evidence they cause cancer, liver damage, and other harmful effects in mammals.

The odd orange coloring is a sign these buds were grown with synthetic PGRs, which are bad for you!

How can you tell if a bud was grown with synthetic PGRs?

  • An over-abundance of orange hairs (orange hairs are natural, but PGR buds typically have far more than normal).
  • Buds may be orange all the way through
  • After being dried and cured the buds may take on a dull brown appearance like it’s been vaped or decarbed
  • Less than normal trichome coverage (little “sparkle”)
  • Buds are tighter and denser than usual for that strain
  • Buds seem small for the weight
  • Buds tend to have rounded smooth edges like each individual nug was vacuum-sealed or pressed (though they could just be vacuumed-sealed or pressed)
  • Buds may feel “spongey” or squishy
  • PGR buds often have a relatively low smell
  • The more PGRs used during the growing process, the more stark the differences

Note: You may find naturally grown buds with some or all of these traits. This is a list of possible clues, but there is no way to prove (without testing) that buds contain PGRs. The fact that it can be difficult to tell is one of the reasons it’s great to grow your own!

What’s the inside like? Here’s an example of natural buds (left) vs. PGR buds (right) after they’ve been ground up. Notice how the PGR buds are orange all the way through. Picture by Toradorkat.

Another example of natural (left) vs. PGR (right) weed

In 2011, it was discovered by the California Department of Food and Agriculture (CDFA) that several common plant supplements contained undisclosed levels of Paclo and Alar, including Bushmaster, Top Load, Gravity by Emerald Triangle, Phosphoload, and a popular supplement called Flower Master.

Over the next few years, these supplements and others were pulled off the shelves or reformulated to remove the PGRs. I remember the hubbub as several commercial producers were upset because these supplements made a huge difference to bud yield and density (just look at the pictures!). Doesn’t that mean we’re now safe from PGRs? Unfortunately, no. Companies are not required to list all ingredients on supplements, and there is evidence some companies still add PGRs.

Naturally dense buds are beautiful. Just watch out for extremely dense buds with rounded edges and unusual orange coloring, especially if you don’t know who grew it!

This strain normally produces completely purple buds but the hairs still came in bright orange.

What about PGRs naturally found in plants? Are those safe to give to weed?

The safety of natural PGRs isn’t well understood. Even though some PGRs come from natural sources, that doesn’t prove for sure that they are safe for humans when given to weed. On the other hand, you have kelp supplements (which have been used naturally for thousands of years) that are now classified at PGRs. Unfortunately, there’s no neat or easy answer.

That being said, I’ve yet to see any evidence that the natural PGRs commonly used for growing have harmful effects on humans. Contact us to share your experience with natural PGRs.

Kelp, alfalfa, and other organic sources contain natural PGRs. Unlike synthetic PGRs, I haven’t seen any evidence that natural PGRs are harmful to humans.

My buds are dense, does that mean they were grown with PGRs?

Just because buds are dense does not mean they were grown with PGRs. If you don’t see the other symptoms listed on this page (orange coloring, spongey texture, low smell, etc.), then chances are the buds are fine.

Here are examples of naturally dense buds grown without any PGRs

Does my supplement contain PGRs?

Just a few years ago, many growers were unknowingly using plant supplements containing synthetic PGRs that weren’t listed on the label. Many of these products were removed from the shelves or reformulated, but some supplements still contain them.

Beware supplements by lesser-known companies that claim to make buds denser, especially if buds turn out like this!

How to ensure you aren’t giving your plants PGRs:

  • Do your research before buying supplements from unfamiliar companies.
  • Contact the nutrient company through their website and ask directly. I’ve been surprised by how responsive and helpful most nutrient companies are when you email them.
  • Beware supplements that claim to keep plants short, halt vertical growth, or make buds more tight/dense. Especially if they’re vague about the ingredients.
  • Or simply skip using supplements altogether. Base nutrients grow high-quality buds and rarely contain PGRs.
  • Consider growing organically (for example, with super soil) or using 100% organic sources of nutrients.

If you grow organically, you don’t need to worry about synthetic PGRs

Synthetic PGRS are dangerous, but how can you tell if they're in your weed? This article will teach you to identify and avoid any cannabis containing PGRs!

Are Plant Growth Regulators (PGRs) in Cannabis Cultivation Harmful?

Sunday February 16, 2020

Few people buying cannabis at a dispensary put much thought into the plant growth regulators that may be present in their product. While growers and producers are intimately acquainted with them, there aren’t many on the consumer end that even know what a plant growth regulator (PGR) is, or their role in a flower’s growth cycle. However, a basic knowledge of PGRs is important for anyone who enjoys weed, as there may be potential health risks involved in consuming PGRs in marijuana.

What Are Plant Growth Regulators?

Plant growth regulators are naturally occurring, hormone-like chemicals specific to plants. The function of PGRs is to mimic or inhibit the expression of a plant’s normal growth hormones during its lifecycle. This includes when the plant begins to germinate, when its fruits ripen and drop, as well as the length, width, and shape of the plant’s roots, leaves, and stems.

PGRs have been used in agriculture and landscaping for nearly a century. Depending on the PGR, their use ranges from increasing the number of apples in an orchard to slowing the growth of grass in a golf course so that can be mowed less often.

Plant Growth Regulators come in two types. Naturally derived PGRs include kelp, chitosan, and trichontanol. Chemically derived, synthetic PGRs include Daminozide (Alar), Uniconazole. These PGRs are sprayed on plants or added into fertilizer to help plants grow more uniformly or to manipulate certain attributes.

How Are PGRs Used in Cannabis Cultivation?

For marijuana, PGRs are mostly used to alter the appearance of the buds, increase yields, or make the plant size more uniform for indoor growing. Some growers also claim that PGRs add to the overall health of the plant, making it stronger and more resistant to disease. However, much of the problems with PGRs, especially synthetic ones, come from less than honest growers looking to increase profitability at the expense of quality and consumer health. This is especially noticeable with how PGR manipulated buds appear after curing.

Much like the fashion industry, the cannabis industry has helped to set an unrealistic standard of beauty on their flowers. Dense, tightly packed buds look much more appealing in the package than fluffier, leafy ones. Consumers may also believe that a luxurious coat of orange hairs means a stronger strain overall. Adding PGRs to a plant can also increase the weight of the end product.

Of course, what determines quality in a bud is the levels of terpenes and cannabinoids contained in the plant’s trichomes, not the shape of the bud. Synthetic PGRs also have a large impact on trichome functions as well.

What Are Some Synthetic PGRs?

Besides being potentially dangerous for human consumption, synthetic plant growth regulators also affect the quality of the plant being grown. Some of the most common synthetic PGRs and their effects are listed below.


This PGR retards a plant cell’s ability to elongate. When used on cannabis, this means that the cells pack much tighter and denser on the flower. While this bud may look like a higher value product, Paclobutrazol actually hinders the development of key terpenes in the cannabis plant. This has a much greater effect on quality than just how the flower tastes and smells.

By hindering the creation of terpenes, it affects how well the cannabis functions on a psychoactive level with the user. THC and other cannabinoids bind much less effectively in their neurotransmitters without those key terpenes due to the entourage effect. Of even greater note, Paclobutrazol also kneecaps the plant’s ability to create the compound THC, which most in the weed community would rank as #1 in importance.


Also known as Alar, Daminozide is used by growers to maximize bud yields. It does this by minimizing the growth of stems and leaves so that the plant can put more resources into flowering. However, like Paclobutrazol, this PGR decreases the production of terpenes, as well as cannabinoids like CBD, CBN, and THC. Basically, it severely restricts resin production in the plant overall, meaning fewer trichomes.

Again, the appearance of a denser nug on a dispensary’s shelf comes at the expense of flavor, potency, and, in the case of PGRs, potentially the consumer’s health.

Chlormequat Chloride

Chlormequat Chloride actually slows down plant growth in certain areas, which in turn helps to encourage flowering. Adding it to plant also can make their size much shorter and more uniform, which makes growing plants indoors a lot easier.

Are Synthetic Plant Growth Regulators Bad for Your Health?

Long story short: yes. Exposure to high doses of synthetic PGRs can be very dangerous to people’s health in both the short and long term. In the late 1980’s, the EPA issued a recall of Alar (Daminozide) for food uses as testing found that it could be classified as a carcinogen in high doses. It’s been banned from human consumption since 1989 and has led to several agricultural recalls. Many synthetic PGRs have been similarly banned as further tests have been done.

The EPA also has concerns that Paclobutrazol might cause liver damage, and may also affect fertility in both men and women. While Chlormequat Chloride has not yet been shown to be hazardous to people’s health, testing is still being done.

Unfortunately, the fertilizers and PGRs used by growers in the cannabis industry are not as tightly regulated as in agriculture. Without a regulatory body overseeing the industry’s standards, unscrupulous growers can use PGRs to improve the appearance of their yields.

Still, even if you’re a heavy weed smoker, you don’t need to run to your doctor for a battery of tests right away. While you should undoubtedly try to avoid ingesting synthetic PGRs, the effects of short term of exposure are not fatal and the amounts in your cannabis are small. You’re at about as much risk from eating an apple with PGRs as you are from the flower you’re smoking through it. But with any potential carcinogen, it’s better to play it safe and avoid it. Over long periods of time, the damage can add up.

How Do I Avoid PGRs in My Marijuana?

The best way to avoid synthetic plant growth regulators is to ask your friendly neighborhood budtender. They should have some idea of their grower’s reputation. You can also call the producers themselves and request information.

If your budtender is uncertain or the producer uncommunicative, there are certain things to watch out for when buying your flower. The first is incredibly dense buds. Of course, dense buds can also be a mark of a master grower, which is why you should make sure they’re also dusted with trichomes.

Synthetic PGRs tend to decrease resin production. This means a less sugary bud overall, which also means a less potent one, since it’ll be lacking those necessary cannabinoids and terpenes. The bud may also be spongy and more brownish but lacking a strong smell. Luckily, with a little knowledge and these helpful tips, it can be easy to avoid buying weed grown with synthetic PGRs. Being a conscious consumer in this regard can go a long way – happy consuming!

What are your thoughts on the use of plant growth regulators in marijuana cultivation? Share them in the comments below.

Cannabis growers are always looking to cultivate the best crops. However, some growers and dispensaries are using plant growth regulators (PGRs) to bring out certain traits in their marijuana flower. Learn more about PGRs, synthetic PGRs, and if they are harmful for humans to ingest.