I’ve always compared potting soil to a cake mix. Add too much salt, not enough flour, and the cake won’t rise. Add chocolate chips or cranberries, and it becomes fabulous. Potting soil is much the same.
Potting Soil Is Not Dirt
But, before discussing potting soil, let’s talk about soil. Go out into the yard, grab a shovel, and dig a hole. That’s soil. Soil can be sandy, loamy, or clayey. Soil can be acidic or slightly chalky. Soil contains organic matter and is inhabited by millions of living organisms, from earthworms to bacteria to mycorrhizal fungi. Soil is alive, in a way, and it’s the amalgamation of all this physical, organic, and biological chemistry that makes plants like to grow in it… or not.
No Soil in Containers!
On a balcony, it’s different. Container growing has its own challenges, and our good old garden soil isn’t equipped to handle those issues. That’s why we turn to potting soils or mixes. These expertly crafted blends allow the substrate to be both light and airy, able to retain an impressive amount of water while ensuring good drainage.
Basically, potting soil is mainly composed of a mixture of peat moss, perlite or vermiculite. Perlite is a lightweight volcanic glass, while vermiculite is a heat-expanded mineral; both help retain moisture and improve air circulation in potting mixes. Some manufacturers shamelessly replace perlite with polystyrene beads. Polystyrene serves no useful purpose in a potting soil mix. Its only purpose is to save money. Add 20% of polystyrene in a mix cuts the costs…
The Secret Ingredients… a Plus!
To this basic potting mix, serious companies add secret ingredients that, much like the chocolate chips or dried cranberries in my cake mix, add value to the product. These might include coconut fiber to better retain water, organic matter in the form of compost or manure, lime to stabilize the pH, a slow-release organic fertilizer, or any other ingredient that can improve the performance of a potting mix.
Although seed starting mix, potting mix, and container mix have many things in common, it is always best to choose soil specifically designed for container growing. The terms “veranda”, “vegetable garden”, “urban”, “patio and terrace”, “balcony” or “flower boxes” are the keywords to search for. In the case of a vegetable garden, most gardeners enrich the soil by adding a good dose of compost, either at the bottom of the pot or mixed with the potting mix.
Look for Quality, Not Quantity!
And my most valuable piece of advice for growing in containers is to not skimp on quality. A quality potting mix will help your plants survive the summer in style! And, back to the cake mix: yes, you can buy a 99-cent box of cake mix and it makes a decent cake. But there’s nothing that beats a good homemade cake, made with quality ingredients. This cake will make you want more.
Help. When I lives in the UK it was easy to get ericacious potting soil for my acid loving plants but herein BC I cannot find it anywhere. What alternatives are there?
Good morning, Thank you for this article. However, I do have two questions. I live in Vermont and do you have specific brands I could purchase here in the United States that you could reccomend for potting soil? Second question is I did not recall in the article once you have found your potting soil do you need to fertilize? If so, what do you use please? Thank you ever so much. Judith A. Meyncke unger@gmavt.net email