By Jim Poling Sr.

The show is starting, but to see it you don’t have to fret about a Covid-19 threat inside a confined theatre. It’s all outside and the indications are it will be a great one.

Nature’s annual autumn leaf colour show depends on fine weather for success and this year is looking good. Weather forecasts into October predict ideal conditions for a colourful show.

Overcast skies, rain and hard frosts diminish fall’s forest colours, says Bill Parker, a research scientist with the Ontario Ministry of Natural Resources and Forestry in Sault Ste. Marie.

“So, if you love the fall for the change in leaf colour, hope for a prolonged period of sunny, dry, and cool but not freezing autumn weather,” he says.
That is exactly the weather predicted for the Haliburton-Muskoka region well into October.

Falling temperatures and less light from shorter days tell deciduous trees that winter is coming and it is time to shut down their food-producing factories, which are their leaves. The leaves contain chlorophyll, a green pigment that captures the light energy that helps to transform water, carbon dioxide and minerals into sugars and starches that feed the tree.
Chlorophyll is the dominant pigment that gives leaves their green colour, says Parker. So dominant that it masks other pigments in the leaves – carotene and xanthophyll and anthocyanin.

As fall advances and chlorophyll breaks down, the masking weakens and the other pigments start to show their colours – the yellows, oranges, reds, crimsons and purples.

Parker says that trees, like people, are genetically different. Their genetic makeup determines the colours they display in fall.

For instance, white birch lack the anthocyanins that produce varying shades of red, so their autumn colours are more in the yellow range. Oaks carry anthocyanins that make for autumn leaf colours ranging from rusty brown to red. Maples have a nice mix of yellows, oranges and reds.
Hillsides offering the most spectacular autumn colours have a good mix of different trees.

How long the autumn leaf show lasts also depends on the weather.
“Hard frosts, and periods of high winds and intense precipitation can accelerate trees losing their leaves,” says Parker.

Environment Canada predicts a gorgeous fall leaf show in Ontario and lots of sunny blue-sky weather for viewing it.

“But don’t procrastinate,” David Phillips, senior climatologist for Environment and Climate Change Canada, has been telling askers. “We’ll be seeing a later-than-usual normal colour change season, but when you get later, you run the risk of getting into some fall storms …”

The risk is real. Data recorded by an Environment Canada site in Haliburton shows rain – a trace or larger amounts – falls on more than half the days in October. In the last five years, rain fell an average of 17.6 days.
However, October is not known as a cold month. The average median temperature for Haliburton over the last five years was 8.08 Celsius.