During the spring and summer, chlorophyll in tree leaves absorbs sunlight to transform carbon dioxide and water into carbohydrates such as sugars and starch for tree energy and growth.
Carbon is digested into the tree and oxygen is released from the leaves. Isn’t it amazing that plants absorb carbon dioxide and give off oxygen, and animals do the opposite? We should be incredibly grateful for this balance on Earth.
Water and nutrients flow up from the roots into the leaf veins. This food-making process, called photosynthesis, takes place in the numerous leaf cells containing chlorophyll, which gives the leaf its green colour.
Along with the green leaves’ pigment are yellow, orange and red pigments; the same pigments that colour our foods; yellow xanthophyll (as in corn and golden aspen leaves), orange carotenes (as in carrots and mountain ash leaves) and red anthocyanin (as in cherries and red sumac leaves). Most of the year these colours are masked in the leaves by the great amounts of chlorophyll’s green pigment.
But in the fall, after a dry summer, when daylight hours shorten, tree leaves stop their food-making process. The chlorophyll (green colour) stops being produced and fades away allowing the other colour pigments (mainly yellow, orange, and red) in the leaves to show off their brilliant autumn splendour.
Deciduous trees and shrubs shed their solar panels to hibernate through winter and take a break from photosynthesizing. The stems of the leaves weaken (without food) and the leaves fall from the trees blown by the wind or pelted by rain.
But what about the needle-like leaves of pines, fir, spruce and hemlock, or scale-like leaves of cedar and juniper – our evergreens? These hardy trees leaves have less surface area and have a waxy coating, plus they produce a type of antifreeze that stops the chlorophyll from drying up. Their needles or scales stay on the trees during winter and keep their green colour. An exception is our Western Larches. Their soft, unwaxed needles turn golden and fall – they’re deciduous (and coniferous).
The best time to enjoy autumn’s sun-kissed, brilliant colours is on a clear, dry, cool day. One of my favourite autumn colour-viewing spots in Vernon is on Rocky Ridge at Turtle Mountain on a sunny, late afternoon. Lumby’s Salmon Trail, just below the highway, is wonderful to hike in shimmering fall colour. So is Mission Creek in Kelowna’s Springfield Park.
I like to collect a small basket of autumn leaves to decorate my home‘s entry. My kids and I played a fall game when we went hiking; each of us tried to be the first person to shout “fall” when a leaf fell from a tree.
Enjoy the colour; it only occurs for a brief period each fall.
And remember — when you see those yellow, orange and red pigments — they’ve been there all along, and autumn is their time to shine.
Roseanne shares her knowledge of the outdoors to help readers experience and enjoy nature. Follow her on Facebook for more.