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Growing things · Ages 3–9

Why do leaves change color?

In autumn, many deciduous trees stop replacing the green chlorophyll in their leaves. As it breaks down, yellow and orange pigments become easier to see. Some leaves also make red pigments.

Read or listen to the story

For little wonderers, ages 3–5

Many leaves have yellow and orange colors hidden by their green. In autumn, the green fades and those colors show. Some leaves make red colors too.

A little deeper, ages 6–9

Chlorophyll helps leaves capture light for photosynthesis. Shorter days help trigger seasonal changes in many trees. When chlorophyll breaks down, other pigments become visible; some trees also produce anthocyanins that look red or purple. Different trees and weather conditions give different autumn colors.

A Whylo Sample Story

Maple's autumn surprise

Samknewthetreebesidethegate.Itslowestbranchlookedlikeacrookedelbow,anditsleavesmadegoodshadeforareadingrug.AllsummerSamcalleditthegreenumbrella.Oneautumnmorning,theumbrellahadayellowpatch.

SamaskedGrandpawhethersomeonehadspilledpaint.Theyinspectedafallenleaftogether.Ithadgreennearthestemandgoldalonganedge.‘Leaveshavedifferentcolor-makingsubstances,’Grandpaexplained.‘Thegreenoneiscalledchlorophyll.Whenitfadesinautumn,someoftheothercolorscanshow.’

Samturnedtheleafover.‘Theyellowwastherealready?’‘Somecolorswere.Sometreesmakeredpigmentsinautumntoo.’Theylookeddownthestreet.Onetreewasgold,anotherreddish,andatallevergreenwasstillgreen.Treesdidnotallchangeinexactlythesameway.

Everyfewdays,Samdrewthetreefromthesamewindow.Thedrawingsbecamealittleflipbook:green,green-and-gold,thenbrancheswithfewerleaves.Samlikedthebarecrookedelbowtoo.Itwaseasiertospotthebirdsperchedthere.

AttheendofthebookSamwrote,‘Mytreechanges,butIknowit.’Grandpahelpedspell‘autumn.’Theyspreadthereadingrugindoorsbesidethewindow,wherethelastgoldleavescouldjointhestorywithoutcominginside.

Sam and Grandpa discover red, yellow, and orange leaves beneath a maple tree.
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Read the full story

Sam knew the tree beside the gate. Its lowest branch looked like a crooked elbow, and its leaves made good shade for a reading rug. All summer Sam called it the green umbrella. One autumn morning, the umbrella had a yellow patch.

Sam asked Grandpa whether someone had spilled paint. They inspected a fallen leaf together. It had green near the stem and gold along an edge. ‘Leaves have different color-making substances,’ Grandpa explained. ‘The green one is called chlorophyll. When it fades in autumn, some of the other colors can show.’

Sam turned the leaf over. ‘The yellow was there already?’ ‘Some colors were. Some trees make red pigments in autumn too.’ They looked down the street. One tree was gold, another reddish, and a tall evergreen was still green. Trees did not all change in exactly the same way.

Every few days, Sam drew the tree from the same window. The drawings became a little flipbook: green, green-and-gold, then branches with fewer leaves. Sam liked the bare crooked elbow too. It was easier to spot the birds perched there.

At the end of the book Sam wrote, ‘My tree changes, but I know it.’ Grandpa helped spell ‘autumn.’ They spread the reading rug indoors beside the window, where the last gold leaves could join the story without coming inside.

What we learned

When green chlorophyll fades, other leaf colors show. Some red pigments are made during autumn.

One more little discovery

Collect a few fallen leaves with a grown-up, without pulling leaves from trees. Sort them by color, then sketch them. Notice whether every tree nearby is changing.

Talk about it together

Why might two trees on the same street look different in autumn?

Our characters and adventures are fictional. Explore the science behind this question:

US Forest Service: Why Leaves Change Color (PDF)

Keep wondering

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