What Are PGRs?

Nov 30, 2023

Plant Hormones & PGRs  -  What the hell are they?

Welcome back to another blog post, this time we will be looking at Plant Hormones & Plant Growth Regulators (PGRs).

There are ultimately two classes of Hormones - Synthetic & Naturally Occurring 

These mysterious compounds can significantly impact plant growth, BUT thats not all...if used incorrectly, PGRs can have adverse effects on plants, the environment and even human health.

Do you know what's inside that bottle of nutrients you just bought?

Time to find out...

*Disclaimer - In this blog post we will refer to naturally occurring hormones as natural hormones and man-made/synthesized hormones as PGR's. Plant hormones and plant growth regulators (PGRs) are related concepts, but they are not the same. Plant hormones are naturally occurring chemical messengers produced by plants to regulate various processes within the plant while plant growth regulators (PGRs) are normally synthetic hormones that can mimic or trick the plant. It is essential to note that the research on this topic is complex and not all PGRs are associated with adverse health effects. We highly recommend that you do your own research and educate yourself so that you can make an informed choice.



PGRs What Are They?

Plant Growth Regulators, commonly known as PGRs, are a group of 'chemical' compounds that are SYNTHETICALLY produced. These chemical compounds influence and regulate plant growth/development and will impact growth by either promoting or inhibiting cell division, elongation, flowering, root growth and fruit development.

Common Plant hormones & The man made alternatives. 


These stimulate cell elongation and are responsible for branching & root initiation. Auxins play a crucial role in phototropism and gravitropism, directing plant growth towards light and gravity.

PGR Alternative: Indole-3-butyric acid (IBA) or naphthaleneacetic acid (NAA)


Gibberellins are involved in stem elongation, seed germination and the flowering process. Gibberellins are known to stimulate stem elongation. 

PGR Alternative: Paclobutrazol or chlormequat chloride


Responsible for cell division and lateral bud growth, cytokinins ensure balanced plant growth and prevent the aging of plant tissues. Cytokinins counteract the inhibitory effects of auxins (on lateral bud growth) which helps to regulate apical dominance. This contributes to a more balanced and even growth pattern.

PGR Alternative: Kinetin or zeatin

Abscisic Acid

Often referred to as the "stress hormone," abscisic acid regulates various stress responses like drought tolerance and seed dormancy.

PGR Alternative: Abscisic acid (ABA) 

Salicylic Acid

Known for its role in plant immunity, salicylic acid is essential for triggering defense responses. It induces Systemic Acquired Resistance (S.A.R), a defense mechanism that enhances the plant's ability to defend itself against a broad spectrum of pathogens or pests.

PGR Alternative: Acetylsalicylic acid


This hormone influences fruit ripening and plays a role in helping plants shed old leaves. 

PGR Alternative: Ethephon


Brassinosteroids aid in cell elongation and division which leads to increased growth. Brassinosteroids will also enhance stress tolerance against extreme heat, dry conditions and even resistance against pathogens.

PGR Alternative: Epibrassinolide or brassinazole (BRZ)


Jasmonates are involved in defense mechanisms, Jasmonates are triggered by stress such as insect attacks and will help plants launch their defense response.

PGR Alternative: Methyl jasmonate (MeJA)



Now that you know what PGRs do to benefit your plants, lets talk about some of the negative affects

(When looking at the negative affects of PGRs we will only be focusing on Synthetic PGRS)

The Impact of PGRs on Plants 

PGRs can be a useful tool in enhancing desired characteristics like fruit size, flower production, and disease resistance but like many things in life you cant just get all the pros without some cons...this is why it is advised that you use PGRS with extreme caution, excessive use of PGRs can lead to imbalanced growth, decreased fruit quality, and plant toxicity. 

Environmental Impact?

When it comes to the environment, the overuse of PGRs can have major negative impacts on the planet. Runoff from agricultural fields can contaminate rivers and water sources which can disrupt aquatic ecosystems. The persistence of synthetic PGRs in the environment raises concerns about their impact on non-target species which includes beneficial insects, birds, and other wildlife. PGR residues may disrupt the natural balance of ecosystems and even affect reproduction in insects and animals. 

PGRs and Human Health?

While PGRs are designed for plants, there is ongoing research that proves synthetic PGRs will have an impact on human health. There are concerns about their potential to disrupt endocrine function, which can affect hormone regulation in the human body and lead to adverse health effects. Concerns have also been raised about certain synthetic PGRs and their potential to cause cancer. Concerns exist about the potential impact of PGRs on reproductive health and development. Exposure during pregnancy or early childhood may have implications for fetal development and childhood growth. Some studies have raised concerns about the impact of PGRs on the central nervous system. Neurological effects, including cognitive and behavioral changes, have been investigated in relation to exposure to certain PGRs.


We are all on a mission to have thriving gardens and heavy harvests, but it's important to understand the role of Hormones both synthetic and naturally occurring.  As responsible gardeners, it is our duty to use (if we decide to use) PGRs wisely, making sure that when we use them, they contribute positively to our green sanctuaries and don't cause harm to the planet, environment, animals or our health.

At Growers Hub we suggest using products that contain naturally occurring Hormones like, Guano, Seaweed, Aloe Vera, Alfalfa, Beneficial bacteria and even compost teas. 

Lets try to garden sustainably and leave this planet in a better condition than we found it 

Stay tuned for more gardening insights



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