Soil recipes

40% Canadian Sphagnum Peat Moss or coco coir 

30% Compost and/or Castings (humus)

20% Perlite, Pumice, Scoria or Rice Hulls

10% Biochar

To the base soil above add per cuF:

1-4 cups Volcanic Rock Dust 

1/2 Kelp Meal 

1/2 cup Alfalfa Meal 

1/2-1 cup Neem and/or Karanja Cake 

Houseplant Soil Blend:

Base mix:

5 parts / 5gal sphagnum peat moss and/or coco coir

5 parts / 5gal perlite or pumice

2.5 parts / 2.5gal worm castings and/or compost 

1 part / 1 gal biochar

Amounts below are per the Gallon measurement, 13.5 gallons total base soil mix as noted above, adjust as needed for the amount you make.

Amendments (fertilizer):

1 cup rock dust

1/2 cup kelp/alfalfa

Recipe Notes:

1. You can use 100% peat moss, 100% coco coir, 50% of each or any ratio in between.  This portion is a light neutral base medium to any potting soil and is pretty crucial for initial root growth, air penetration and water retention.  Over time microbial life and worms in the soil will aggregate and homogenize all of the organic matter in your soil and within a year there won’t be any observable difference in the organic matter in your soil (compost vs peat/coir). 
2. In place of peat moss or coir you can make leaf mould at home, if you’re up for the challenge see our article below on peat moss vs. coco coir for more details!
3. If using Rice Hulls be aware it does decompose so it will not be a permanent source of aeration.  You might consider using 10% rice hulls with 10% perlite, pumice or scoria plus 10% biochar and that will provide an excellent 30% initially to get started and 20% long term is plenty.  As you can see from recipe 2, I am comforrtable with as little as 10% total long term (biochar).
4. Rock Dust is my main source for ongoing mineral/nutrients in these recipes, the amendments in recipe 1 can be interchanged with any number of amendments you might want to use or have better access to.  They are short term nutrient sources and I personally like starting with these to help kickstart growth for the following reasons:
   1. Kelp: Wide range of macro/micro nutrients, hormones and enzymes
   2. Alfalfa: High in Nitrogen, phytohormones
   3. Neem/Karanja: High in nurients, particularly Sulphur, and includes pest prevention compounds to help prevent soil borne pests like fungus gnats and root aphids.
5. The quality of your starting compost is the most important part of a potting soil! Starting with a high quality humus source will make the entire process that much easier.  The lower quality/quantity humus (compost and castings) one starts with can lead to poor plant growth whether it’s due to lack of nutrients, soil life, anaerobic conditions and so on.  Do your research, find out what is available locally and start with the best material you can! 
6. Making your own is an excellent choice and you can control exactly what goes into it including pre-composting your soil amendments. There are plenty of resources out there to help start your own composting projects and I at least urge everyone to keep a simple pile or bin for your kitchen and yard scraps!

Mixing Soil

How you mix your soil will depend on how much you need.  You can mix right in your container or bed with a shovel/rake. You can mix in a storage tote and pull from there as needed.  Larger amounts you can lay out a tarp and use a shovel and rake as well as folding the corners of the tarp towards the opposite corner to fold the material onto itself, in between rakes and shovel turns.  One can rent or borrow a cement mixer, I personally don’t like this method as you end up witih many pockets on unmixed ingredients inside the mixer but many people do prefer a cement mixer.

Reference our soil mixing video on instagram or tiktok but I like to mix the ingredients in this order.

1. Peat moss and/or coconut coir mixed with your perlite, pumice and rice hulls first.  Now you have your neutral base material together.
2. mix compost with biochar and amendments.  This is an important step for me as it is soil life in the compost that will break down the amendments and it is the biochar that will both house microbes as well as store nutrients.
3. Then mix these altogether and you’re ready to use your soil!
4. In the end, it really doesn’t matter which order you mix your ingredients but the process noted above has worked easiest for me but as long as all the ingredients get mixed together evenly is all that matters!

Sphagnum Peat Moss:

Sphagnum peat moss not only contains nutrients but is also full of beneficial bacteria and fungi including mycorrhizae. 

Compost/Castings:

This can be in the form of Thermophilic compost, worm castings/vermicompost or leaf mould.  Sourcing quality humus is key to growing vigorous and healthy plants from the beginning.  

Biochar:

Biochar retains 10-12 times its weight in water (think: drought tolerance), stimulates microbial growth and diversity in the all important rhizosphere (increased yields), acts as a ‘reservoir’ for nutrients thus reducing ongoing fertilizer requirements.  Incredibly porous increasing Oxygen content in the soil, and of course sequesters carbon.

Rock Dust:

Rocks and their eventual dissolution (hence, rock 'dust’) is the original source of ALL nutrition on earth, minerals!  

Rock dust is the source of nutrients, Humus is the delivery system. Soil life feeds off the rock dust and in turn makes it plant available.  The closer your source of rock dust is to the consistency of powdered sugar (like ours) the quicker they become available.  Through the exchange of plant root exudates the microbes living in the rhizosphere are able to deliver the elemental minerals derived from the rock dust directly into your plants.  

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1. If you are in North America I would suggest Canadian Sphagnum Peat Moss. In the rest of the world (South America, Asia, Australia, Europe etc) I would recomend coconut coir. This is in relation to reducing the distance the raw material has to travel to you.  In regards to peat moss, Europe has a very long history of using peat to heat homes, as fuel, and peat bogs are greatly depleted, I would check the source of your peat and make sure you are comfortable with where it is coming from.  In Canada the peat pogs are extensive, great environmental restrictions and guidelines are in place to not only prevent excessive harvesting but there is a limit to what can be harvested from one location and is then returned back to nature.  It has been shown that more sphagnum moss grows each year than is harvest making it a renewable resource at the current rate of harvest.
2. If using more than 50% of coconut coir it is suggested to add 1/2 cup gypsum (or other sulphur amendment) per cuF to account for the lack of S in coconut coir.  Coconut coir is also lacking in soil bacteria/fungi and other nutrients that sphagnum moss contains.  Good compost or castings will counteract this but it is something to take note of.
3. Coconut coir is often touted as the sustainable option to peat but it is important to understand the extreme rate of growth coconut farming undertook in the last 20 years to satisfy the coconut oil/water craze.  Many native rainforests were destroyed via slash n’ burn to acquire the land to grow the worlds coconut oil/water.  Insecticides and salt-based fertilizers are used to farm coconuts while none are used in the harvesting of peat.
4. “Canada has 113 million hectares (280 million acres) of peatlands, nearly one-quarter of the entire world’s production space. Of this, the industry, over its 60-plus years of activity, has used only 29,000 hectares (72,000 acres). This is .02% of the country’s peatlands.” 
5. In contrast there is currently about 12 million hectares of coconut in production, 12 million hectares of tropical ecosystems taken away to grow coconuts. That’s 413.8x more land dedicated to growing coconuts than of harvesting peat.  None of the land being farmed for coconuts is being returned to its natural state.
6. “Our use of best management practices to restore peatland is founded on the 30-plus years of research conducted by the University of Laval through the Peatland Ecological Research Group (PERG). This Group has developed, through peer reviewed research, a technique that will return the harvested peatlands to peat-accumulating ecosystems. Through the application of the moss layer transfer technique, the restored harvest sites:
   • Have typical bog plant biodiversity cover established within three to five years following restoration and is dominated by sphagnum mosses
   • Have organic matter values restored that are comparable to those of natural systems
   • Have their water table rise quickly, improving hydrological conditions. Research suggests that it will take between 15 to 20 years to accumulate a thick enough moss layer that will again regulate the water fluctuations. 

• Have carbon emission reduced and can return to net annual carbon sinks after a decade to 15 years post-restoration.”

1. I live in California and have determend Canadian Sphagnum Peat Moss is the best option for me to create potting soil.  I provide all of the above information not to persuade one to use this or that input but to hopefully provide better insight on the production of both products so that we can all make better informed decisions on what is best for our location.  
2. 70+ years ago, prior to the use of peat moss or coconut coir, pests, diseases and poor quality plants was often the result of digging up native soils and putting them into containers.  If one wanted to grow plants in containers they would enter their local forests and waterways and find the best quality softest, lightest soil they could find which was often in and around creeks, watersheds, forests where years and years of decayed leaves accumulated.  If we did not have access to Peat moss or coconut coir, we might have a more serious issue on our hands with over harvesting local ecosystems.  The extent that people at home would be able to garden and grow plants indoors would certainly reduce.  Every material we use in the modern world started as a raw natural material and energy/fuel was used to move it from it’s origin and into your home.  Of all the raw materials we use I think those used for gardening, growing our own food and plants, improving the soil in and around our homes and communities is a positive use of natural resources and the more we can all collectively grow plants naturally without the use of synthetic fertilizers and pesticides the even greater positive impact we can create.
3. If one lives in the right part of the world and has the patience….Leaf mould is an excellent substitute for peat and coir if you have access to it or the material and patience to  make it.  You woul essentially make a pile of fallen deciduous tree leaves in autumn and occasionaly turn it for 1-2 years and eventually it will be a lightweight, airy textured, rich humus similar to peat or coir.  If, for example, I lived on property in the Northeast United States or Canada I would certainly make this a home project next to the kitchen compost pile! 

https://www.thespruce.com/making-and-using-leaf-mold-2539475

https://www.greenhousegrower.com/production/media/how-the-canadian-peat-moss-industry-is-working-to-restore-peatlands/

https://peatmoss.com/restoration/

https://www.science.org/content/article/claim-coconut-oil-worse-biodiversity-palm-oil-sparks-furious-debate

https://rainforestjournalismfund.org/stories/coconut-products-gain-popularity-certification-essential-sustainability

https://rainforestjournalismfund.org/stories/palm-vs-coconut-oil-whats-more-sustainable-choice

https://www.agrifarming.in/coconut-farming

There’s consideral confusion about Perlite & Pumice in particular and that’s interesting because all three are the same material, amorphous volcanic glass. :)

Perlite

Also known as pearlstone, a natural glass and similar in composition to obsidian.  Perlite is formed from the rapid cooling of viscous lava or magma.  When crushed perlite is rapidly heated water held inside is converted to steam.  Tiny bubbles form in the softened rock and perlite is expanded up to 20x its original size.  

~5 million tonnes are produced annually with Greece, Turkey, Western US being the largest producers, alogn with Hungary, Italy and Georgia.  

There has been many numurous studies done on perlite dust to ensure worker safety and despite common rumors there is no glass pieces in the dust that cut and is legally classifed as “nouisance dust.”  Of course, if one is sensitive to dust in general they should wear a mask when mixing, but studies have shown it poses no harm. 

https://www.perlite.org/wp-content/uploads/2018/03/health-effects-perlite.pdf

Pumice

Volcanic glass formed during explosive volcanic eruptions when highly gaseious liquid lava is ejected into water or air as a froth containing masses of bubbles and rapidly cools. Pumice is light enough to float on water and usually light in color. Found wherever volcanos are with 21 million tonnes commercialy produced each year with highest amounts in Italy, Turkey, Greece, Iran, Chile and also in western united states.

 Mineral Comp.    Pumice / Perlite 

Silicon Dioxide:       76.2% / 70-75% 

Aluminum Oxide:    13.5% / 12-15%

Ferrous Oxide:          1.2% / .5 - 2% 

Sodium Oxide:          1.6% / 3-4%

Potassium Oxide:     1.8% / 3-5%

Calcium Oxide:         0.8% / .5 - 1.5% 

Magnesium Oxide:   0.05% / .2-.7% 

Scoria

Many might be more familiar with the names “volcanic rock” as sold in big box stores or “cinder” sold very cheap in landscape yards. Scoriaceous basalt, as its full name, is the heaviest of the three and usually darker red, brown or black in color depending on location.  Scoria is formed when gases in magma expand to form bubbles as lava reaches the surface.  The bubbles are retained as the lava solidifies.  There is greater variation in mineral composition of scoria because of its density but is also dominated by silicon dioxide like perlite and pumice.

Logistically speaking, pick whichever you prefer, whichever is convenient or local to you. Perlite is the lightest to handle and ship, pumice a pretty far second and scoria the heaviest.  While it provides sufficient aeration it provides the least, but if purchased from a local landscape yard (ask for cinder) it can by far be the most cost effective option.

Worth noting: More than 50% of all Perlite, Pumice and Scoria is used in construction with horticultural use being one of the smaller categories of use behind other industries.

Fun Fact:   LECA/Hydroton, or expanded clay (Haydite), was invented in 1917 when the clay was super heated to 2100F causing it to expand and become porous, it was this invention that later lead to the discovery of heating perlite to expand and become porous.