Trees are complex organisms. And the reason why leaves turn colour in the fall involves some advanced biochemistry. Through the process of photosynthesis, a tree will absorb energy emitted by the sun and use it to convert carbon dioxide and water into sugars and oxygen. Leaves contain a pigment called chlorophyll (chloro is the Latin word for green) which gives them their verdant colouring. When autumn's colder weather comes around the chlorophyll starts to break down, and new colours start to surface. Yellow and orange leaves appear due to the emergence of pigments called carotenoids (carrots get their orange colour from a pigment known as carotene). Some trees, like the maple, produce a pigment called anthocyanin, giving their leaves an intense red colour. The stronger any of these pigments are within an individual tree, the stronger the colours.
“There’s a clear correlation between environments that get colder in the fall and the amount of red produced,” says David Lee, a botanist from Florida International University in Miami. “Red maples turn bright red in Wisconsin. In Florida, they don’t turn nearly as bright.” This fall you can impress your friends when you tell them how autumn colours come to be.