Fall colours expected to be 'drab' in southwestern Ontario

The vibrant colours of southwestern Ontario's fall foliage will be less than spectacular with hot, dry conditions affecting tree cover.

Vibrant reds likely to fall short with hot and dry conditions

Yellows and browns will likely dominate as the weather continues to be hot and humid. (David Donnelly/CBC)

The vibrant colours of southwestern Ontario's fall foliage will be less than spectacular this autumn, according to a biology professor.

It's because the recent hot, dry conditions in the region are having an affect on the tree cover.

"You're probably going to be seeing much more drab foliage and that's not exactly what we get in our cars to look at on the weekend," said Danielle Way, assistant biology professor at Western University. 

Sugar maples likely won't be producing the brilliant red leaves. Instead, expect yellow and brown leaves to dominate the landscape this year.

Way told CBC's London Morning that multiple days of near record-breaking high temperatures are causing trees to continue producing chlorophyll at a time when production is usually slowing down, 

When the weather gets cold, a tree produces the red colour pigment that makes for eye-popping foliage. But Way explains the tree it is actually doing it to protect leaves from the cold and bright sunlight. 

"Early in the morning on those cold fall days, you need the [red] pigment to help protect photosynthesis because the leaf can't cope with the light." 

15 days of no rain

Dry weather is also a factor in the well-being of a tree, Way said, noting some will be stressed by September's drought-like conditions.

Data from Environment Canada shows there have been 15 days of no rain in the London region and across much of southwestern Ontario.

"It's the little trees that are more at risk of drought stress because they don't have a big stem or a big root system."

Way recommends giving smaller trees a good soak with a hose, letting it run for up to an hour, allowing the water to penetrate the root system. 

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With files from London Morning