How do we know?
↻ One of the pages with a moving picture
Scientists are still working out the best colors.
- Summer leaves are full of green chlorophyll. It catches sunlight so the tree can make food.
- Yellow and orange are in the leaf all summer, but the green hides them.
- As fall days get shorter, the tree stops making chlorophyll, so the green fades.
- Some leaves make new red and purple in fall, using bright light and extra sugar.
Scientists don’t fully understand every reason for the best colors. They know pigments, night length, the kind of tree and the weather all play a part.
Warm sunny days and cool, but not freezing, nights seem to bring the brightest colors.
In the Great Smoky Mountains, colors start up high and move down. Vermont is famous for its sugar maple colors.
Wow number
3× Most plants have about 3 times as much green chlorophyll as yellow and orange colors.
Myth or fact?
Leaves need a freezing night to turn bright colors. Myth. Warm sunny days and cool, but not freezing, nights seem to bring the brightest colors.
The yellow in fall leaves was there all summer. Fact. The green chlorophyll was just covering it up.
Think about it
Why do you think some trees, like pines, stay green all winter?
Where in the world?
Great Smoky Mountains, Tennessee and North Carolina, USA where fall colors start up high and move down. Vermont is famous for its sugar maple colors — 35.6118° N, 83.4895° W.
Where these facts come from
Every number on page 63, and who measured it
This page tells us about the green, yellow and red colors in leaves, and what makes the best fall colors.
A U.S. Forest Service fact sheet, kept in the U.S. government's online library
govinfo.gov/content/pkg/GOVPUB-A13-PURL-LPS95750/pdf/GOVPUB-A13-PURL-LPS95750.pdf
We checked it on 31 October 2026
This page tells us that leaves have about three times more green than yellow and orange.
Autumn Colors — The Texas A&M Forest Service
tfsweb.tamu.edu/education-outreach/learning-about-trees/autumn-colors
We checked it on 31 October 2026
This page tells us how fall colors move down the Great Smoky Mountains.
Fall Colors — The U.S. National Park Service
nps.gov/grsm/planyourvisit/fallcolor.htm
We checked it on 31 October 2026
This page tells us about Vermont's famous sugar maples.
Rise and Fall of Foliage (U.S. National Park Service) — The U.S. National Park Service
nps.gov/articles/the-rise-and-fall-of-foliage.htm
We checked it on 31 October 2026
Has this changed?
Yes, this one may grow. Scientists don’t fully understand every reason for the best fall colors.
The colors also change from year to year with the weather.
Words from this page
- chlorophyll
- The green stuff in leaves that catches sunlight.
- pigment
- A natural coloring in a leaf, a flower or skin.
Try it!
Sort fallen leaves by color.
1. With a grown-up, collect fallen leaves from the ground (don’t pick them off trees). 2. Sort them into piles: green, yellow-orange, red-purple and brown. 3. Which pile is biggest? Check again next week and see if it changes.
What happens: as fall goes on, the green pile shrinks and the other colors grow, as chlorophyll fades and hidden colors show.
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