Why Do Leaves Change Colour in the Fall?

Introduction

Ontario’s fall colours aren’t just pretty—they’re science in action. Here’s why the forests burst into reds, oranges, and yellows each autumn.

The Science

• Chlorophyll, which makes leaves green, fades as daylight shortens.
• Carotenoids, responsible for yellows and oranges, are revealed.
• Anthocyanins form in cool nights and sunny days, giving brilliant reds.

Insider Tip

Red maples in Algonquin show anthocyanins most vividly, while Niagara’s vineyards glow gold from carotenoids. Hamilton offers late bursts of both, making each region unique in colour variety.

Reader’s Questions

Q: Do all trees change colour at once?
A: No—maples peak earlier, oaks often hang on later.

Q: Why are some years brighter?
A: Weather. Sunny days and cool nights enhance reds; dull seasons usually mean cloudy or wet weather.

Closing Thought

Knowing the science makes the show even more special. Experiencing it across Ontario’s landscapes—from Algonquin’s reds to Niagara’s golds—is the best classroom nature can offer.