What's In Your Potting Mix?


Potting mix dates back to the Hanging Gardens of Babylon and the Pharaoh's palace of Ancient Egypt, if not earlier.  Ancient horticulturalists created specialized mixes for potted plants from ingredients on hand, like tree bark and manure, to create a lighter, more drainable mix of ingredients that kept roots (and plants) healthy in an enclosed environment.


Fast forward several millennia to the 1960s, upstate New York.  A group of scientists and horticulturalists at Cornell University invented the first commercial potting mix - a combination of peat moss, vermiculite, perlite and fertilizers.  This "Cornell Mix," as its known, has served as the basis of commercially-produced potting mix formulations sold in the USA since.

This invention - and its commercialization - changed the gardening industry forever.  Previous to the Cornell Mix, plants in nurseries were typically grown in the ground and dug up for customers as needed.  A stable, reliable potting mix consistent from batch to batch allowed nurseries and farms to grow plants in container off the jump, creating a more consistent and portable product for customers.  Potting mixes also allowed for more versatile use of space - plants that can be easily moved eliminates a number of obstacles, such as inclement weather and resulting loss, as well as easier stocking and merchandising options. 

The world has changed significantly since the 1960s.  Potting mix, however, has not.  

The main ingredients in potting mix still include vermiculite, perlite, gypsum, and peat moss - all mined resources that are finite and not sustainable.  The lineup of core ingredients in the Cornell Mix reflects a very different time in American history, when an understanding and appreciation of mining's impact on the environment was poorly understood and researched.  

Table published in the 1972 Cornell Information Bulletin of "Cornell Mix" variants designed for different plants. (via:  Garden Culture Magazine )

Table published in the 1972 Cornell Information Bulletin of "Cornell Mix" variants designed for different plants. (via: Garden Culture Magazine)


Since this time, both research and man-made natural disasters have shaped our understanding of mining's impact on local ecosystems and communities.  Libby, Montana comes to mind as a key example. 

Vermiculite, a key ingredient in potting mixes, was first discovered in Libby in 1919,  and was marketed under the commercial name Zonolite for commercial use in the construction industry.  Grace Mining Company took over the mining operations in the 1960s, and heavily marketed vermiculite as a consumer product for gardening.  

Throughout this time, Grace Mining Co. also knew that the vermiculite in Libby's mountains was laced with asbestos.  This co-mingling of minerals is common a natural occurrence in vermiculite deposits.  Typically, the amount of asbestos co-mingled with vermiculite deposits is low and within a safe zone for mining workers and surrounding communities.  In Libby's case, however, the amount of asbestos present was extremely high - 80% or greater of the vermiculite ore was asbestos.  

During its time running the Libby's mines, Grace Mining Co. actively denied there were issues with the mines despite the fact that a notable portion of the mine's workers started developing lung diseases and lung cancer caused by asbestos exposure.  To make matters worse, Grace Mining Co. distributed leftover vermiculite to the town's playgrounds, baseball fields, and other outdoor spaces, spreading the asbestos-contaminated vermiculite throughout the town and exposing its youngest citizens to dangerous levels of airborne asbestos.  

The level of contamination surrounding the town is, in fact, so high that asbestos fibers have permanently lodged themselves in the surrounding forests - an unprecedented challenge for the EPA when it comes to clean up and remediation.  When the EPA stepped in in 1999 and declared the town a superfund site in 2002, asbestos-related fatalities were 20-40 times greater than non-asbestos related deaths (2).

"Permaculture Principle 5: Use & Value Sustainable Resources"

The 12 Permaculture Principles offer an alternative paradigm to understanding modern issues and creating effective solutions.  The mainstream approach to gardening and agriculture is that nature is something to be contained and managed.  Permaculture takes an alternative approach, looking to nature's patterns for guidance.  

A key concept in the permaculture principles - zero waste systems.  In other words, creating environments and systems designed to be self-sustaining.  This concept is both tangible and literal - ie. design your garden to use edges and margins - as well as a philosophical guideline when it comes to sourcing products and materials.   

Take, for example, the ancient gardeners of Babylon and Egypt who used remnants of other industries in their community to create potting soil.  Unlike these predecessors, we live in a "flat" world whose boundaries exist only on maps.  We are all part of an international community and village, and need to shift our perspective appropriately.


One major opportunity - coconuts.  Coconuts are versatile, and used in consumer products ranging from Coco Water to shelf-stabilizers in packaged goods like cookies and crackers.  This versatility has increased demand for coconuts significantly over the last ten years.

The byproduct from harvesting and processing coconuts is coconut coir - the tough husks and mulch from the coconut and tree.  Coconut coir has the same benefits as peat, vermiculite, perlite and other amendments added to make potting mix light and arable - and also has many benefits over these commercial alternatives.  As a raw product, coco coir is extremely light-weight, and leaves a small carbon footprint vis a vis fossil fuel use for transport. 

As someone who works with clients daily to develop and source products, I understand (and can attest to) the issues inherent with making major sourcing changes.  Ideally, if you're planning on creating a product for mass distribution, you want to purchase raw materials years out to keep your pricing stable should a shortage occur.  Facilities are set up to create a specific product from specific materials, and employees are trained accordingly.  Making a major change to any aspect of your product's sourcing comes with large, up-front costs to change these systems. 

This said, we're at a point where the world is changing - and continues to change - rapidly.  Debates about causality aside, these changes require companies to be more adept and nimble when it comes to how they source and make their products.  The gardening and agricultural industry is far behind on this front, especially when it comes to potting soil. 



Gro-Intelligence Footnote (3)

Gro-Intelligence Footnote (3)


This issue is one example among many.  Industries tend not to change until they have to.  Consumers can play a vital role in this change.  No executive in the world will produce a product that has no market.  

Over the next year, we'll be exploring six ways to grow greener.  We'll also be developing six alternatives to common, commercially-sold products that are sustainable, natural, organic, and non-toxic that will:

a. Raise awareness by creating an educational, hands-on experience

b. Provides a product that's higher quality and performs better than commercial alternatives at a comparable price


If you hadn't already guessed, our first of six ways will focus on potting mix (stay tuned - we'll be launching next week).  We want your input on what we should do next:



Footnotes & Further Reading

(1) "Who Invented Potting Mix?" Garden Culture Magazine. 

(2)"Libby, Montana". Asbestos.com

(2) "Naik et. al.  "Mortality from asbestos-associated disease in Libby, Montana 1979–2011." J Expo Sci Environ Epidemiol. 2017 Mar; 27(2): 207–213.

(3) "Cuckoo for Coconuts: Demand Is Soaring, but Production Isn’t Keeping Up" Gro-Intelligence.