Why do some leaves turn red or yellow in autumn?

In one line

The rule

In autumn, many plants stop making chlorophyll (the green pigment), so other pigments (colours) in the leaf become visible, making leaves turn yellow, orange, or red.

Let's understand it simply

Imagine you have a green roti with a little bit of haldi (yellow) and lal mirch (red) mixed in. As long as the green chutney covers everything, you only see green. But if you wipe away the chutney, the yellow and red colours appear.

Leaves are like this. In summer, leaves are green because of chlorophyll (the green colour chemical). When autumn comes, the plant stops making chlorophyll. The green fades away, and the yellow and red colours (which were always there, just hidden) start to show.

How it works

1. In spring and summer, leaves make lots of chlorophyll to catch sunlight.
2. Chlorophyll gives leaves their green colour.
3. When days get shorter and cooler in autumn, plants stop making new chlorophyll.
4. Old chlorophyll breaks down and disappears from the leaf.
5. Other pigments like carotenoids (yellow/orange) and anthocyanins (red/purple) become visible.
6. The leaf now looks yellow, orange, or red instead of green.

The story behind it

Scientists noticed this colour change long ago, especially in places with cold autumns. The study of why it happens helped us learn about plant chemistry and how plants get ready for winter. The word "chlorophyll" comes from Greek, meaning "green leaf."

Where you see it in real life

• Mango trees in autumn: Leaves turn yellow before falling off — the green fades, yellow shows.
• Gulmohar trees: Leaves can turn reddish or orange before dropping.
• Maple trees (in cold places like Kashmir or Himachal): Bright red and yellow leaves in autumn.
• Neem trees: Leaves may turn yellow as they dry up.
• Fallen leaves in parks: You see many colours, not just green.

Why it matters

• Shows how plants prepare for winter by saving energy.
• Helps farmers know when trees will shed leaves and rest.
• Used in gardening to choose colourful plants for parks and gardens.
• Important for understanding plant life cycles in science.

Common mistakes

• Thinking the leaf "gets" new colours in autumn — actually, the colours were always there, just hidden by green.
• Believing all trees change colour — only some do, especially in places with cool autumns.

Remember it

When green goes, hidden colours show — that's why leaves turn red or yellow in autumn.