In this The Scene in TO article, John Ransom from Davey’s Toronto area discusses the factors that played into Toronto trees changing color early this year. 

Posted: September 24, 2025

Vibrant red leaves very close in frameAs summer fades and Toronto cools down, the city’s tree canopy begins its annual transformation. From High Park’s oaks to the maples along the Don Valley, one of the most beautiful sights in our city is the shift from lush green to fiery reds, oranges, and yellows.

“Many people think the first cool night is what makes the leaves turn,” says John Ransom, a local ISA Certified Arborist with the Davey Tree Expert Company in Toronto. “In reality, it’s a mix of conditions, like moisture, sunlight, and tree health all coming together to create the brightest colours.”

So, what’s really behind the show? It comes down to four key pigments: 

Chlorophyll: The source of green throughout the growing season. As it breaks down in the fall, hidden colours emerge.
Carotenoids: Responsible for the yellows we see in maples and birches. Present all year but masked by green until autumn.
Anthocyanins: Produce the vibrant reds and purples, especially after sunny days followed by cool nights.
Tannins: The pigment that turns leaves brown just before they drop.

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The Davey Tree Expert Company provides research-driven tree services, grounds maintenance and environmental and utility infrastructure consulting for residential, utility, commercial and environmental partners in the U.S. and Canada. Established in 1880 and headquartered in Kent, Ohio, Davey has over 12,000 employees who create and deliver sustainable solutions. Davey continues to grow through expertise with the SEED Campus, its newest commitment to training, research and safety. Become part of the Davey legacy by applying today and join one of the top ten largest employee-owned companies in the U.S.

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