Tree Care Articles

Soils - 1

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Written by Kevin R. Lee Kevin R. Lee
Published: 15 December 2019 15 December 2019

Soils and watering, these two crucial aspects of life in your garden, form the essential basis from which everything else comes, either beauty and thriving health or a yard full of problems, with the trees doing poorly, infested with insect pests and the usual diseases associated with each tree.

It is well to speak of natural soil layering and use technical Russian terms for the various types and layers, but that has nothing to do with the modern suburban garden. If you explore soil science, you will find a lot of Russian words, as the Russian soil scientists were the first in the field, so to speak. Their names and classification systems are in use world wide. As you move around any given locale, these small-sized pieces of old pastures and woodlands, with their inherent natural soil zones, do still exist, but in the modern suburban neighborhood, they are long gone.

Gone where? When construction of a new subdivision begins, the first major change is the careful stripping away of all the surface soil, the loam. It is usually a blackish brown color, full of organic material and the vast microscopic community that is the life that inhabits all good healthy soils. It is carefully removed and hoarded; later it will usually be mixed with a variety of poorer soils, poorer from a tree’s perspective. that is, and will be available for sale. Soil is like any other valuable commodity. Let’s stretch the comparison to olive oil; on the one hand there is a first press organic extra virgin, on the other is a low grade later press, full of extractive chemicals and mixed with different cheap oils. They can be and are both called extra virgin olive oil, just as strange soil mixtures are called loam.

Let’s go back to our evolving new suburb. With all of the top soil gone, we are into the second natural soil layer, which in the Calgary area is a tawny sticky clay. This level is completely useless to plants, one they will rarely grow into. There are a number of reasons for this; firstly, clay soil particles are so small that the spaces between them, called pores, are so small that the natural movement of air, water and nutrients is severely inhibited. Roots that attempt entry into this zone meet with saturated, nearly airless, conditions, too wet and with little available oxygen for the normal sugar-burning respiration that the roots’ life processes require. During the process of a tree removal years ago, a homeowner had stripped away all the loam as part of the garden reconstruction. The roots of the small tree were exposed, plain to see. The roots ran out in various directions, all of them right above the clay zone with none penetrating into it.

With the valuable loam removed and squirreled away, construction can begin. The services are deeply buried, roads paved, and houses completed. The last thing, and it seems least important to the developer, is the landscape. Typically each property will be covered with some "top soil", turf installed and two trees planted.

What about that black soil? Ideally it would be 18 inches deep and be the soil that was initially removed. So we could dream. What happens is that high grade soil is sold to companies who will later resell it, but making their product go as far as possible. In some of the cheaper mixtures, all sold as loam or top soil, large chunks of nearly pure clay have been evenly mixed throughout. Have a good look, it’s like raisins in a pudding.

A quick visual soil test involves nothing more than picking up a handful and squeezing it. The darker black it is the better. We don’t want it too wet, moist is best. Grab a handful and squeeze it into a clump, now break up the clump. Does it crumble, showing that it has a granular structure or does it stay in a sticky ball? Good loam, the real stuff, needs to be fairly wet to form a clump. It has a granular nature that easily breaks up once clumped. Soils with higher clay content are grey or tawny in color and are sticky when wet. Form a clump of this in your hand; it will not crumble. It will just ooze like something you saw at your potter friend’s studio.

Good soil has a distinctive smell, very hard to describe, other than by saying it has the smell of good, rich, cultivated, loved soil. Soil that has a promise in it, that promise says you can grow wonderful plants with this soil. Damp, rich, earthy, once experienced, never forgotten, a smell like Grannie’s garden.

Once the house is finished a layer of "top soil" is spread over the clay, and on top of this a layer of sod. If you are fortunate to be the first owner and you want to get serious about gardening, have them skip the sod and install your own quality loam, about a foot deep, then plant and garden to your delight. There is no reason why the labor of removing the sod be done, bury it under your foot of new soil. It will die and become nothing more than a lower layer of organic material.

As low in cost as these poor mixes are, they are still grudgingly applied to new properties. There are areas in some of the newer sub-divisions, built quickly during the last boom, where the new homeowners have trouble even growing grass. Trees would not thrive. Some of these "top soil" applications were as shallow as six inches.


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