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The why and where of autumn leaves' cavalcade of colour (10 photos)

The fall colours are here and Back Roads Bill teaches us a leaf lesson

Deep in the forests, little lines of red, yellow and purple flames are kindling a fire of colour that sets ablaze the back roads.

Hearing the leaves fall with the wind and rustling the fallen ones while shuffling your feet is way better than TV, live streaming and all those digital pic apps put together. It is time to play in the leaves.

It is a spectacle for all to admire and one of the reasons why northerners look forward to the changing of the seasons. And contrary to popular belief it is not Jack Frost and his paintbrush that are responsible for the colour change. We need to go back to school for a colour primer.

Back to school

While you were playing in the hot sun during this summer past (top five warmest summers since 1948) trees were working hard to keep you cool.

To feed the shiny green leaves that make shade, trees use sunlight to convert water and carbon dioxide into sugar. This is called photosynthesis. A good many syllables in the word and we learned about the process in science class some time ago.

The teachers told us leaf colour comes from pigments. Pigments are natural substances produced by plant cells. The three pigments that colour leaves are: chlorophyll (green) carotenoid (yellow, orange, and brown) anthocyanin (red).

Chlorophyll is the most important of the three. Without the chlorophyll in leaves, trees wouldn't be able to use sunlight to produce food.

Carotenoids create bright yellows and oranges in familiar fruits and vegetables. Corn, carrots, and bananas are just a few of the many plants coloured by carotenoids.

Anthocyanins add the red to plants, including cranberries, red apples, cherries, strawberries and others.

Chlorophyll and carotenoid are in leaf cells all the time during the growing season. But the chlorophyll covers the carotenoid - that's why summer leaves are green, not yellow or orange.

Trees respond to the decreasing amount of sunlight by producing less and less chlorophyll. Eventually, a tree stops producing chlorophyll. When that happens, the carotenoid already in the leaves can finally show through. Is this all you will need to know for the colour change test?

There’s More Eh!

Broad-leaved or deciduous trees such as beech, birch, maple and birch have been growing since the spring but are now beginning to slow down before they reach a dormant stage during the winter. There are many factors as to why we don’t see those dramatic changes until the colours are upon us.

Guylaine Thauvette is a Registered Professional Forester, recently retired from the now Ministry of Northern Development, Mines, Natural Resources and Forestry at the North Bay District office.

"If we give trees human characteristics, we can say that individual trees assess their food production rate and decide when it’s best to start shutting down for the winter,” said Thauvette.

“Leaves have the brightest colours when the days are bright and cool, and night temperatures are just above freezing. Vivid colours are also the result of specific recipes of red, yellow and orange pigments. Different tree species have different leaf colours and change colours at different times. The colour and timing are also different between trees of the same species growing side by side.”

There is more to learn, she said.

“One of the factors that affect the red colour is the sugar content in the leaves, which is higher in maples. The sugar content varies from tree to tree and leaf to leaf."

"The red pigment itself is not bright. It’s the mixture of the red with the yellow and orange that produces the bright reds, deep oranges and pink reds," Thauvette said. "Oak and cherry can also have bright foliage, and these have lower sugar content. Oak, cherry and maples can also have deep purple leaves. These result from the mixture of brown pigments with the other colours.”

“If you see one red tree in a forest of green, pay attention to it. That same tree will likely be the first to turn red every year. It’s just the way it is,” she said. Based on her observations, both sugar/hard maple and red/soft maple develop deep reds. “I don’t believe that one is more brilliant than the other. Sugar maple, in general, grows larger crowns than red maple and this is what makes hard maple so attractive.”  

What about the bonus question.

'Wait a minute; teacher, is this a red maple or a sugar maple (where we get the real maple syrup)?'

As Canadians, we should know our maple leafs, right? After all, it’s on our flag (our 1965 Canadian flag, stylized). But do we know the differences between a sugar maple leaf and a red maple leaf?

The leaf margins tell the main story: sugar maples have smooth edges while red maples are toothed or serrated. The three lobes of a sugar maple’s leaf are separated by smooth, U-shaped valleys – think “U” as in “sugar.” The red maple’s lobes, meanwhile, are separated by serrated, V-shaped valleys. Overall, this makes the sugar maple’s leaves broader and more rounded than the narrower, pointier leaves of the red. And for colour, the sugar maple will turn to shades of yellow, orange and red sometimes on the same tree. Although you may expect the leaves of the red maple tree to blush a deep scarlet in autumn, some varieties blaze yellow instead.

Where to Go!

Where should you go to see a breathtaking symphony of reds, yellows (browns) and oranges?

Go for a ride on the back roads the colours will be just around the next corner.

As in the classic movie, ‘Casablanca,’ when Captain Renault (Claude Rains) says to his constables with Rick (Humphrey Bogart) close by, “… roundup the usual suspects...”

Some popular and dramatic locations across the north include Duschenay Falls/College trails accessed from both ends and the escarpment trails; a popular Highway 17 roadside stop just west of the regional hospital in North Bay.

In the southern corridor, there is a “real keeper” the Stormy Lake trail to the fire tower just before you enter Restoule Provincial Park.

You will view one of the most striking contrasts of colour with a backdrop of very white rock at the “Crack Trail” on the way into Killarney Provincial Park, south of Sudbury. You will come to the 'crack,' scramble up and at the top have one of the finest views in Ontario, including many lakes below, rock-knob hilltops, with Georgian Bay in the distance.

Onaping Falls is a well-known stop on Highway 144 within Sudbury and journey a little further on Highway 144 and discover the Osprey Heights Trail, a hidden gem, part of Halfway Lake Provincial Park on the east side of the highway.

If you are near Sault Ste. Marie, find Roberston Cliff on the Voyageur Trail system, just north of the “Soo;” further along Highway 17 is Lake Superior Provincial Park and its many trails.

Looking for yellow and browns, find the new High Falls trail within the City of Timmins and there is plenty of boreal colour within Esker Lakes Provincial Park east of “KL City.” Take your bikes to René Brunelle Reni Provincial Park at Moonbeam for a moving fall experience.

The Brits say autumn; fall is a magical time, follow the colour change online

Thanksgiving is upon us. It’s only for a few short weeks that our hillsides are alive with colour. The majesty of red, orange, yellow and purple should be understood and appreciated for their splendour.

It is a free show produced by nature to colour our world with its sights, sounds, feelings and emotions. Just lie down and cover yourself up with leaves like you did a while back.


Bill Steer

About the Author: Bill Steer

Back Roads Bill Steer is an avid outdoorsman and is founder of the Canadian Ecology Centre
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