Recent reports say that parts of Eastern Canada have spectacular fall colours this year, and the pursuit of “leaf peeping”, as it’s known back East – viewing and photographing fall colours – is in full swing.
With our temperatures dropping to single digits, and the season’s first snow dusting the North Shore Mountains this past weekend, it’s the right time to do a little local “leaf peeping.” While we don’t have whole mountainsides covered with deciduous trees – our dominant trees are evergreens – we still have some real beauty to enjoy. We just have to look a little closer.
Our native red-leaved species include the red-osier dogwood above – a common shrub in our parks, and the vine maple, a small tree which can be a spectacular contrast to the dark greens of our forest conifers.
So why do some trees’ leaves turn red, and others yellow? It’s all about the chemistry of leaves. As the amount of daylight declines in the fall, leaves stop making food through photosynthesis. The food maker, the green stuff of leaves, is chlorophyll. In fall it stops being replaced by the tree or shrub, and slowly degrades and disappears from the leaves revealing the yellow pigments previously hidden.
Here’s an example of a big-leafed maple – our large, native maple – showing the process in action. As the green chlorophyll disappears, the yellow pigment is revealed.
In technical terms, the degrading chlorophyll slowly fades to reveal the xanthophyll pigments in the leaves. For trees with red fall leaves, a slightly different, but related process takes place. The decline in chlorophyll is accompanied by the production of anthocyanins (red pigments) related to the end-of-season increase in sugar production and storage in the trees. Red-osier dogwood shows this process well.
Our bright red street trees undergo the same changes, but most of them are Eastern imports planted for easy maintenance, and of course for their spectacular fall colours.
So while we don’t have mountainsides of red, we have our fall beauty on a smaller scale.
And finally, just to show the birds haven’t been ignored this week, here’s a vine maple nicely setting off the blue of a Steller’s Jay. You’ll have to look closely to see it. Can’t see it? Click the image to enlarge it, and take another look. When I took the picture, I didn’t know I’d captured the bird too!