Understanding Soil

Updated: Oct 9, 2018

The Basics Series, as the name suggests, is a series of articles that lay out some of the basics of gardening and plant care – Soils, Mulches, Planting and Staking, Roots & Water, and Plant Fertilization. Our hope is that this series will be accessible to the beginning gardener while also offering some additional information that will prove valuable to those who have been digging in the dirt for a little longer (first lesson: dirt is what’s tracked onto your carpet, soil is what we plant into). If, along the way, you would like additional information on a particular subject, or if you have suggestions for additional blog posts please feel free to leave them in the comments below.


“It’s simple; just stick it in the dirt, green side up, and give it some mulch!” says the gardener who, in the coming weeks and months, will be losing some percentage of the plants they just bought.

Henry David Thoreau once wrote “Our life is frittered away by detail. Simplify, simplify.” The sentiment of such a statement is easy to grasp given the complex schedules, myriad appointments, and endless responsibilities that we all have this side of eternity. Simplify – you’ll probably live longer. But it’s not the full story, I’d argue. Simplicity, for most of the processes we engage in life, is only valuable when some understanding of the underlying complexity is dealt with. Joggers have a simple exercise regimen based on an understanding of the complex systems of the human anatomy. If they go beyond what that anatomy can handle, problems may arise. Airplanes simply fly, due to an understanding of the complexity of aerodynamics and propulsion. With no understanding of complexity, airplanes wouldn’t get off the ground.

So it is with soil for the gardener. “Green side up” is simple, but without some understanding of the underlying complexity of soil, that simplicity can lead to endless troubles and a lack of what we’re really striving for – great gardens and landscapes.


So, what is some of the complexity of soil that should be considered? Glad you asked!

It has been estimated that there are as many as 100 million bacteria and 800 feet of fungal threads in one teaspoon of garden soil (Who did the counting and measuring? I have no idea, but their patience and eyesight should both be commended). While these are numbers and stats that we can’t really get our mind around, their importance can’t really be over-stated.

Soil is composed of both organic and inorganic matter - sand, silt, clay, minerals, decaying leaves, weeds and debris, etc., and all of them play a significant role in keeping your garden plants happy and productive.

But back to the microbes. Those millions of bacteria and football field lengths of fungi that inhabit each teaspoon of soil in your garden can be thought of as little garden machines performing a simple task in a complex system. The fungi and the bacteria – the microbes, I’m going to start calling them – are the very machines that turn leaves and debris into the dark brown and black soil that our gardens long for. The microbes basically chew it all up and spit it all out. Beyond this, they continually break down many of the minerals that are naturally found in the soil and even those (fertilizer) that we add to the soil as supplements.

So what? Most of the minerals in the soil, whether they’re naturally occurring or synthesized (most store-bought fertilizers are synthesized compounds of naturally occurring elements), are locked in a form that is unusable to the plants that we are trying to feed. As they are, the plants can’t benefit from these fertilizers any more than they can benefit from a credit card or a pet goldfish. The microbes, however, hold the key. The microbes convert the nitrogen, phosphorus, and potassium into forms that the plant can take up and benefit from. As I mentioned earlier, the importance of soil microbes cannot be overstated. They are the little machines that make it all work.

Soil drainage is also an important factor to keep in mind when your mind is in the garden as most of us are trying to grow more tomatoes, coreopsis, and oak trees and fewer bog plants, rice paddies, and waterlilies. The sand and the minerals (think itty bitty bits of broken rock) allow the soil to drain well. This is important because the roots of the plants you are trying to grow require both drainage and pore space (the gaps between the soil particles). They need water, sure, but they also need to be able to breathe. Without good drainage, the pore spaces will remain filled with water and the roots of your heirloom tomato will begin to rot. The sand and minerals in our soils contributes reliably to drainage because they break down far slower than a leaf, thereby allowing water flow and keeping pore spaces open.

But good drainage isn’t only about how quickly the water moves through the soil. It’s about balance. Good soil needs to be able to drain but it also needs to be able to maintain - it needs to be able to hold some water. Do you know what helps to keep some of the water in the soil? Microbes again! Remember, it’s the microbes that are breaking organic matter down into their basic components and, as they do, they create a compost that not only nourishes our gardens, it also maintains water content. Long live the bugs!


Green side up? True. But an added consideration of the complexity of soil will go a long way toward more enjoyment in your gardening and landscape maintenance pursuits.

“But wait! What if I suspect my soil is out of whack? How do I bring the balance?” We’ll discuss balance and soil correction in our next post, entitled Balance in the Soil – Amendments and Their Kin. Until then, please leave any comments or questions in the space below.

Read More in The Basics Series

The Basics Series: Balance in the Soil - Amendments and Their Kin

The Basics Series: Planting and Staking

The Basics Series: Roots and Water

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