Changing Colour of Leaves in Gatineau Park

There are a number of interpretive programs that the Gatineau Park puts on. One of these that I attended in the fall was called Follies of the Fall Forest.

Peter Dudley also wrote about this a few weeks ago in his blog.

For several weekends during the most colourful season people are invited to find out more about the park’s trees.

Genevieve Pilon talked to children and adults first inside the visitor centre and then guided us through the Sugarbush Trail identifying various species of trees and talking about their adaptations for their various ecological niches.

Genevieve first explained that much of the colour of the fall leaves is actually there all the time but masked by the green colour of chlorophyll; the stuff that enables the leaves to create sugar out of sunlight.

Here she is showing some of the kids how colours are hidden using food colouring and water.

One of the reasons that trees like maples shed their leaves in fall is that leaves depend on water to be able to do their jobs.

In winter water is ice, leaves are useless to the trees and so the trees get ready to shuck the leaves by growing a thin corky layer at the base of each stem.

Once the tree begins to cut off circulation to the leaves the chlorophyll gets used up and the yellow and orange begins to show through.

The yellow and orange is from another kind of chemical called carotenoids that shows up all over nature making flamingos pink, lobsters red and carrots orange. The chemical gots its name through Latin from the same source that gave carrots their name.

The red leaves of the Gatineau Hills get their colour in a different way and it this colour that makes some years flamingly glorious and other years just bright and beautiful.

Especially in maple trees as the tree begins to shut down, some sugars are left in the leaves. When nights are cool and days are sunny these sugars undergo another chemical reaction turning them into something called anthocyanin; another chemical named for what it colours, this time from Greek meaning “flower blue.”

It’s looking up at a cold night sky, then getting most of the sunshine that makes the top part of maple trees sometimes more red than the bottoms.

I’ve heard several authorities say that the fall colours start based on the tree’s perception of shorter daylight hours, and Genevieve said so too. But it seems to me that in years when warm weather stretches deep into fall the colours come later. I don’t know if this is my memory playing tricks on me but it’s nice to know that there is a scientific reason why some years the fall foliage seems more beautiful than others.

Here’s a map of where we walked.