Trees and Calgary skyline

A client I have known for some time now lives on Joliet Avenue in upper Mount Royal. Today, there is nothing unusual about the house or property: inner-city suburbia, a well-kept area. What is interesting about this property are the historical photos, taken in the early 1900s when the house was just completed. The pictures prominently show three things: sky, prairie, and this one single house. These are good photos. From south of the house looking north, you can see the edge of the escarpment several blocks north and, far away across the river valley, the other escarpment where Crescent Heights would soon be built. But to me, the most arresting detail that these photos reveal is that there are no trees. Not one single tree to be seen. At that time, to find trees you would have had to look into the river valley or in coulees or have gone into the young city where the residents were working hard to grow some shade.

Calgary was built upon a treeless plain, the northwest corner of the Great Plains of North America. This isn’t to say that that trees won’t thrive here; all it says is that naturally few trees grew here. Those that did were near a natural water source.

The urban forest we live in today is a testament to earlier generations who wanted to soften the hard glare of the summer sun and the cutting edge of the winter winds. If you plant a lot of trees and keep dumping that Bow River water on them, a prairie oasis can be built. This is really the only strategy that works here: water, water, water.

When the first settlers arrived in the late part of the 19th century, they would have found four native trees. The river valley held three of them: the Balsam Poplar, a towering cottonwood, was a source of building material and fuel. The north-facing slopes of the river valley contain two evergreens, the Rocky Mountain Douglas Fir and the White Spruce. The last of the four, and perhaps the bravest, is the native Aspen, which grows up on the hills near coulees. That’s it. All other woody plant material in Calgary is either shrubby, not of tree stature, or introduced.

Soils in the Calgary area were good initially, but very little of our natural soil horizons now exist. The only place where our natural soils would now occur is in natural parks, such as Nose Hill, and other small, select, undisturbed areas. The native topsoil developing under our vast grasslands for over 10,000 years is excellent, but shallow, with an average depth of about a foot.

Once these soils are disturbed for farming or development they start to deteriorate. Unless a great volume of organic material is replaced annually, they lose richness and vitality. The undisturbed prairie always returned everything it grew, with a few dead bison thrown in for seasoning.

If only our topsoils were used, our gardens and lawns would be in much better shape. Demand far outstrips supply, and almost all of Calgary’s soils are mixed with varying amounts of our native subsoil, clay. This clay is made of tiny particles of glacial till. These particles are so small that no usable space exists between them, usable to plants, that is. Plant roots require oxygen for the process of respiration. Like us, they burn sugars with oxygen. Plant roots avoid pure clay. I have seen tree roots growing along the surface of a clay layer, but they never grow into it.

Most new districts are not supplied with enough topsoil. If you buy a property in one of these, it is a great opportunity to amend your soils with a thicker layer of better-quality soil.

As for Calgary’s climate, living close to the Rocky Mountain front can be a challenge. We live in a land of extremes, never boring, and sometimes downright dangerous. It is this set of extremes that make it such a difficult place to be a tree. Most treed areas have relatively stable conditions throughout the seasons and the winter usually stays cold. Trees hate the freezing and thawing, freezing and thawing cycle. A nice break for us, the warm Chinook winds play havoc with the trees. These winds have a powerful dehydrating effect. This is why a good, deep fall drink is so important. All considered, maybe we are lucky with our four stalwart natives!

(Photo credit: “Calgary from Tom Campbell hill" by davebloggs007, licensed under CC BY 2.0.)