Written by Grant Wood
Artists who paint are very familiar with the colour wheel, and its various segments. The wheel represents the colours we can see, and their relationship to each other. There are several variations of the color wheel, with some including the tones, tints, shades and hues. Colours speak to us, not in the traditional sense, but they instill feelings and emotions within us. For example: red is a warning colour, a colour that demands your attention. This is why ‘stop’ signs and emergency vehicles lights are red. Many companies use this to their advantage, using red in their company logos; do an internet search for the phrase, ‘food company logos’, and see how many use the colour red. Why – because it demands attention and draws your eyes to the logo.
Question - do the colours of trees and shrubs also apply to the colour wheel? You be the judge. When you are walking along the Meewasin Trail, or at any of the many Meewasin sites, look at the beautifully coloured trees and shrubs: which colour draws your attention the most? You got it – red, closely followed by orange and yellow; adjoining colours on the colour wheel. Orange, yellow, and really dark red (almost purplish) may not grab your attention as much, but they still get you to look at them. Hence, why ‘yield’ signs are yellow.
Saskatchewan is often too harsh an environment for many of the large trees that are known for their stunning red autumn colouration in the forests of eastern Canada. We do however have several native trees and shrubs with some amazing red, orange and purplish coloured autumn leaves. All of these can be seen along the Meewasin Trail, and include: chokecherry, dogwood, gooseberry, hawthorn, highbush cranberry, native roses, pin cherry, and poison ivy.
Why do some leaves change colour in the autumn, anyway? For most of the growing season, most trees and shrubs have green leaves. They are green due to chlorophyll, a pigment in the leaf that plants use for photosynthesis. In the autumn, there is poorer quality sunlight, shorter days, and cooler temperatures, all of which cause chlorophyll to break down and disappear. When this happens, other pigments in the leaves become more visible, the most common of which are orange and yellow and their hues. Red leaves are caused by a chemical reaction: sugars in the leaves and cool temperatures react to form a red pigment called anthocyanin.
The autumn colours of a leaf are genetically determined but environmentally modified. This means that although a trembling aspen or Manitoba maple’s leaves traditionally turn yellow, in some years you may find that some turn red. Genetics say that the leaf will probably turn yellow, but temperatures, day length, and quality of light may overrule, causing some leaves to turn red. Autumn colour depends a lot on environmental conditions.
If you are walking along the Meewasin Trail inside the city, remember that there are several introduced tree and shrub species which can be found growing along the river, and many of these can turn a beautiful red, orange, or purplish colour in autumn.
Keep enjoying the beautiful Meewasin Trail and keep watching for the red leaves.
GW
Grant Wood