DIY Potting Soil Mixes

I have some of the worst soil on the planet right here.  I can look down at the valley below me and see cows grazing on respectable pastures.  Up above on the mountain, my soil science daughter says the dirt is ok.  Not fabulous, but ok.  But right here?  It can’t even be called crap.  Crap would be a significant upgrade.  Basically, the previous owner/builders scraped part of the mountain away to make a level pad for building the house, scraped a little more around the house for a yard and driveway, and filled in with something worse than crap as needed to level things out.  To their credit, they did put in a little fenced garden area with some nice topsoil. 

So last year as we replaced the very boring grass with edible landscaping, we also ran an experiment of sorts.  Becky’s professors told her that Nevada had some of the best soil in the country; it was just lacking water.  So to humor Becky, we planted a few shrubs and seeds in the worse-than-crap dirt and added water and fertilizer.  Having already gardened on the side of a mountain in our previous location, I knew better.  And I spent the spring and summer digging holes and removing the worse-than-crap stuff, filling the holes in with compost, and topping them with all kinds of potting soils and gardening mixes—whatever was discounted from Home Depot. 

It took Becky only a short time to see that at least as far as our little corner of Nevada was concerned, her professors had rocks in their heads. 

I got the amazing discounts on soil amendments and flowers because I was Home Depot at the right time every week.  Unfortunately, with the way things are going and the skyrocketing prices of fuel, I won’t be able to justify a weekly shopping trip into town.  I might be lucky to go once a month.  That means I better stockpile the soil amendments for making my own potting mixes here.  While they won’t be cheaper than the 90-95% off that I got with the pallets of broken bags at HD, it also won’t be like I’m paying $10 for a bag of Miracle-Gro and $50 for a trip to town. 

Before getting to the recipes for making your own, keep in mind that there is a difference between potting soil and potting mixes.  That difference is whether the blend contains soil.  Potting soil contains soil.  Potting mix does not.

The potential ingredients include the following:

·       Organic matter is used to add structure, nutrients, and beneficial microbes while helping to retain water.

o   Coconut coir—comes in bricks that need to be re-hydrated before using.  A bit expensive, but environmentalists consider it a better choice—if that’s important to you. 

o   Coffee grounds—if you have them, they add good structure to the soil and trace amounts of nitrogen.

o   Compost—lightweight, nutrient-rich matter that feeds plants and helps retain water.

o   Peat moss—common ingredient in commercial mixes, frowned up by environmentalists who believe the peat bogs shouldn’t be depleted.  Peat moss should be moistened prior to combining with other ingredients.  Peat moss helps aerate the soil and retain moisture.  Peat moss is also rather acidic and soils and mixes made with it may need to include limestone to adjust the pH.  Rotted sawdust and leaf mold are possible substitutes.

o   Worm castings—provide nutrients and help keep soil light and loose.

·       Inorganic matter is added to improve drainage and aeration.

o   Limestone— this alkaline mineral is critical to maintaining a proper pH when peat moss is used.  The ratio is 1/4 cup crushed limestone to 6 gallons of peat moss, or ½ teaspoon per quart.

o   Perlite—this volcanic glass poofs when heated and then is able to hold moisture really well.  And it also helps keep soil light and loose.  It really improves drainage.  Perlite should be moistened before combining with other ingredients to reduce the dust (which should not be inhaled). Sand is a good substitute. 

o   Sand—improves drainage and aeration.  This should be coarse sand (construction or building sand, not play sand).  Do not use sand with clay-ey soils.

o   Vermiculite—a mineral that helps retain moisture and keep soil light and loose.

·       Topsoil—from home improvement stores or your garden.  Make sure it is light and loose.  It should also be pasteurized to prevent weeds or diseases from killing seedlings.

·       Pelleted time-release fertilizer—feeds the plants in a controlled manner.

·       Organic fertilizer

 

Here are a few recipes.  There are “bare bones” recipes as well as more complex options.  An there are even formulas for seed starting and seed transplanting mixes.

Note:  A “part” is whatever you want it to be—a cup, quart, gallon, bucket, yogurt container—whatever.  Measurements do not need to be precise.

Also, all DIY potting soils and mixes, especially those using peat moss, should ideally be tested for pH before planting. 

Potting Mixes

·       1 part peat moss

·       1 part perlite or vermiculite

 

·       2 parts peat moss (or coconut coir for those concerned about peat bog mining)

·       1 part perlite (even though it looks like Styrofoam, it’s totally natural volcanic rock)

·       1 part finished compost

 

·       6 gallons peat moss

·       6 gallons compost

·       4.5 gallons perlite

·       1 ½ cups complete organic fertilizer

·       ¼ cup lime

 

·       20 parts coconut coir

·       10 parts perlite

·       10 parts vermiculite

·       1 part sand

·       1 part pelleted time released fertilizer

Potting soils

·       1 part pasteurized topsoil

·       1 part peat moss

·       1 part sand, perlite, or vermiculite

 

·       6 parts compost

·       6 parts pasteurized topsoil

·       2 parts perlite

·       2 parts spent coffee grounds

·       2 parts worm castings

Seed starting mix

·       2 gallons peat moss

·       2 gallons compost

·       1 gallon coarse sand

·       3 tablespoons lime

Seedling transplant mix

·       2 gallons peat moss

·       2 gallons vermiculite

·       1 gallon fine compost

·       3 tablespoons lime

·       2 tablespoons organic fertilizer

Links to related posts:

How to Pasteurize Potting Soil 

Stealth Gardening 

References:

https://www.theprairiehomestead.com/2015/04/homemade-potting-soil-recipe.html

https://www.motherearthnews.com/organic-gardening/how-to-make-your-own-potting-soil-zmaz08djzgoe/

https://www.almanac.com/how-make-your-own-potting-soil

https://oldworldgardenfarms.com/2020/04/09/potting-soil-recipe/

https://leafyplace.com/potting-soil-mix/

https://theindoornursery.com/blog/expert-tips-for-diy-potting-mix/

https://savvygardening.com/diy-potting-soil/

https://extension.psu.edu/homemade-potting-media

2 june 2024