Questions kids askLiving things
Why do leaves change colour in autumn?
Leaves change color in the fall because, as the days shorten and cool, trees stop making chlorophyll, the green in a leaf, and the yellows and oranges that were there all along show through.
How to explain it, by age
This is how Pukki answers the question, once for each of the five age bands it speaks to. Pukki is a voice-first AI encyclopedia for kids: a child asks out loud, and it gives a short spoken answer made for their age.
For a 3- or 4-year-old
Leaves change colour because trees stop making the green in their leaves in autumn. Then yellow shows, like hidden paint, and some trees add red. Which leaf colour can you spot?
Edited. Pukki said “Leaves change colour because trees stop making their green food in autumn. Then yellow and red colours show, like hidden paint.” The green is not food: it is chlorophyll, which helps the leaf make food. And only the yellows were hidden. Red is made new in autumn. (SUNY College of Environmental Science and Forestry)
For a 5- or 6-year-old
Leaves change colour in autumn because trees stop making the green that helps them make food. The green fades, revealing yellow and orange colours that were already hiding inside the leaves.
Edited. Pukki said “Leaves change colour in autumn because trees stop making as much green food.” The green is not food. It is chlorophyll, the part of a leaf that uses sunlight to make food. (SUNY College of Environmental Science and Forestry)
For a 7- or 8-year-old
Leaves change colour in autumn because trees stop making as much green food-making pigment when sunlight gets weaker. The green fades, revealing yellow and orange colours that were already inside the leaves. Some trees also make red pigments before their leaves fall.
For a 9- or 10-year-old
Leaves change colour in autumn because trees stop making as much chlorophyll, the green substance that helps them use sunlight to make food. As the green fades, yellow and orange colours that were already in the leaf show through, and some trees make red pigments too. A leaf can contain several colours at once.
For an 11- or 12-year-old
Leaves change colour in autumn because shorter days and cooler weather make trees stop making as much chlorophyll, the green substance in leaves. As the green fades, yellow and orange colours that were already there become visible, and some trees make red pigments too. The fallen leaves help return nutrients to the soil.
A little more, for you
A leaf is green because of chlorophyll, which takes in sunlight and uses its energy to turn carbon dioxide and water into sugar. All summer the leaf also holds yellow and orange pigments, hidden under the green. When daylight shortens and the weather cools in the fall, the leaf stops making food and the green fades.
Reds come from pigments the leaf makes new in the fall, which is why some trees turn scarlet while others only go yellow.
Questions to ask them
- What colors are the leaves outside right now?
- Which tree near us changes color first?
- Where do you think the green goes?
These two parts are ours. In the app, Pukki writes its own for every answer, under “Explain it to me” and “Ask them back”.
Try it together
Find leaf coloursLook for fallen leaves and spot yellow, orange, red, and brown.
Pukki’s own idea, given to the parent with one of the answers above.
One more why
Where these answers come from
We asked Pukki this question ourselves, once for each age, on 2 October 2026. No child’s question is published here. The answers are written by AI, and we read each one against the sources below. Two of the five are marked Edited, with what we changed and why.
Pukki’s answers vary from one asking to the next, and can be wrong. It answers in the English its device is set to; these were asked in British English. Today Pukki also ends most answers with a short question on the same topic, which a parent can turn off.
Read against these sources on 5 October 2026.