Why do some leaves turn yellow or red in autumn?

In one line

The rule

In autumn, many plants stop making chlorophyll (the green pigment), so other pigments like carotenoids (yellow/orange) and anthocyanins (red) become visible in the leaves.

Let's understand it simply

Imagine you have a green roti made with spinach. If you wash away the green part, you might see the yellowish colour of the wheat underneath. In leaves, the green colour comes from a chemical called chlorophyll (makes food from sunlight). When the plant knows winter is coming, it stops making chlorophyll. The green fades away, and the yellow and red colours, which were always there but hidden, now show up.

How it works

1. In summer, leaves are full of chlorophyll, so they look green.
2. When autumn comes, days get shorter and cooler.
3. The plant stops making new chlorophyll because it is preparing for winter.
4. The old chlorophyll breaks down and disappears.
5. Yellow and orange pigments (carotenoids) and red pigments (anthocyanins) become visible.

The story behind it

Scientists studied why leaves change colour for many years. They found that chlorophyll is not the only pigment in leaves. The other colours were always there, just hidden by the strong green. This discovery helped us understand how plants get ready for winter.

Where you see it in real life

• Mango tree in autumn: Leaves turn yellow before falling off — chlorophyll is gone, yellow shows.
• Gulmohar tree: Leaves may turn reddish or orange — anthocyanins and carotenoids show up.
• Maple trees (in hill stations like Shimla): Leaves turn bright red or orange in autumn.
• Neem tree: Leaves turn pale yellow before dropping.
• Fallen leaves in parks: You see many colours — each leaf shows its hidden pigments.

Why it matters

• Helps plants save energy for winter by stopping food-making.
• Shows us how plants adapt to seasons.
• The colours make parks and gardens beautiful in autumn.
• Used in school science to explain plant life cycles and adaptation.

Common mistakes

• Thinking leaves "get" new colours in autumn — the colours were always there, just hidden by green.
• Believing all leaves turn red — some only turn yellow, some brown, and some do not change much.

Remember it

When green goes, hidden colours show — autumn leaves reveal their true colours.