Why do leaves change colour in autumn?

In one line

The rule

Leaves change colour in autumn because the green pigment (chlorophyll) breaks down, revealing other colours that were hidden before.

Let's understand it simply

Imagine you have a green crayon and you colour over a yellow drawing. You only see green. But if you erase the green, the yellow shows up. In leaves, the green colour comes from a stuff called chlorophyll (the part that helps plants make food from sunlight). When autumn comes, days get shorter and cooler. The plant stops making chlorophyll. The green colour fades, and other colours—like yellow and orange—start to show. These colours were always there, just hidden under the green.

How it works

1. In summer, leaves make lots of chlorophyll, so they look green.
2. When autumn starts, days get shorter and cooler.
3. The plant stops making new chlorophyll because it prepares for winter.
4. Old chlorophyll breaks down and disappears from the leaves.
5. Yellow and orange pigments (carotenoids) that were always in the leaf now become visible.
6. In some trees, red or purple colours (from anthocyanins) also appear.

The story behind it

Scientists have studied leaves for a long time. They found that chlorophyll is needed for photosynthesis (making food). In the 1800s, scientists learned that other pigments like carotenoids and anthocyanins are also in leaves. These pigments help protect the leaf and give it colour. The study of why leaves change colour helps us understand how plants get ready for winter.

Where you see it in real life

• Maple trees in parks: Leaves turn bright red or yellow in autumn because chlorophyll fades away.
• Gulmohar trees: Their leaves turn yellow before falling off.
• Neem trees: Leaves become pale and then brown as the green fades.
• Fallen leaves on the ground: You see many colours—yellow, orange, red—because the green is gone.
• Gardens in North India: During October-November, many trees show colourful leaves before winter.

Why it matters

• It shows how plants prepare for winter and save energy.
• It helps farmers know when trees will shed leaves and when to plant new crops.
• It makes parks and gardens look beautiful in autumn.
• It is a sign that the plant is stopping food-making and getting ready to rest.

Common mistakes

• Thinking the colours appear because something new is made in autumn. (Correct: The colours were already there, just hidden.)
• Believing all trees change colour. (Correct: Only some trees, like deciduous trees, do this.)
• Thinking the leaf dies as soon as it changes colour. (Correct: Colour change happens before the leaf falls.)

Remember it

When green fades, hidden colours in the leaf appear—autumn is nature’s magic show.