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Why Does North America Have Bright Red Fall Leaves?
October 10, 2025 at 01:17 PM EDT
By WeatherBug Meteorologist, Andrew Rosenthal
Prime leaf-peeping time is here for some! And who doesn`t enjoy watching the trees change from green to yellow, orange, and red? But, did you know that red-colored leaves are unique to North America and eastern Asia, and aren`t found in Europe? Why is that?
According to a 2009 study, even though the same maple and oak trees exist in both North America and Europe, the New World trees have evolved over the years to fend off various predators causing a veritable rainbow of colors to develop.
All leaves, no matter where they are, produce chlorophyll and carotenoids throughout the summer. Chlorophyll is a chemical produced by the leaves from sunlight, and its concentration is reduced as daylight shortens and the colder temperatures take control. As a result, the carotenoids - the same chemical responsible for the orange color in carrots - start to dominate the leaves, changing the colors from green to yellow and orange.
What`s different in North America is the presence of yet another chemical, anthocyanin. This is only produced during the fall when the trees are at their weakest. Anthocyanin helps to limit the sunlight reaching the weaker parts of the leaves, but more importantly may be unwelcoming to pests such as insects and animals. Anthocyanin dominates over the carotenoids, changing the leaf color to a gorgeous and fiery red.
The 2009 study says that as mountains developed across the continents, the trees started to evolve. The mountain chains on this continent - the Appalachians and Rockies - are both north to south oriented, allowing insects and animals to travel from warmer to colder climates and back again. Thus, the trees adapted the anthocyanin to fend off those pesky pests. However, in Europe, mountain chains such as the Alps and Pyrenees are west to east, keeping predators where they were and reducing the need for a protective chemical.
Check the WeatherBug Fall Foliage report each weekend, and when you`re out viewing the brilliant colors, be sure to remember the gift that science has provided you!
According to a 2009 study, even though the same maple and oak trees exist in both North America and Europe, the New World trees have evolved over the years to fend off various predators causing a veritable rainbow of colors to develop.
All leaves, no matter where they are, produce chlorophyll and carotenoids throughout the summer. Chlorophyll is a chemical produced by the leaves from sunlight, and its concentration is reduced as daylight shortens and the colder temperatures take control. As a result, the carotenoids - the same chemical responsible for the orange color in carrots - start to dominate the leaves, changing the colors from green to yellow and orange.
What`s different in North America is the presence of yet another chemical, anthocyanin. This is only produced during the fall when the trees are at their weakest. Anthocyanin helps to limit the sunlight reaching the weaker parts of the leaves, but more importantly may be unwelcoming to pests such as insects and animals. Anthocyanin dominates over the carotenoids, changing the leaf color to a gorgeous and fiery red.
The 2009 study says that as mountains developed across the continents, the trees started to evolve. The mountain chains on this continent - the Appalachians and Rockies - are both north to south oriented, allowing insects and animals to travel from warmer to colder climates and back again. Thus, the trees adapted the anthocyanin to fend off those pesky pests. However, in Europe, mountain chains such as the Alps and Pyrenees are west to east, keeping predators where they were and reducing the need for a protective chemical.
Check the WeatherBug Fall Foliage report each weekend, and when you`re out viewing the brilliant colors, be sure to remember the gift that science has provided you!