Why leaves change colour

Why does a green forest turn gold and red?

In summer, leaves are bright green, and in autumn they blaze with yellow, orange and red.

The green comes from a tiny helper inside every leaf called chlorophyll.

• Green = chlorophyll

Chlorophyll catches sunlight, and the leaf uses that light like a tiny kitchen to make food for the tree.

The yellow and orange colours were always hiding in the leaf, but the strong green covered them up.

In autumn the days get shorter and cooler, so the tree gets a signal to get ready for winter.

With less light, the tree stops making new chlorophyll, and the old green slowly breaks down.

As the green fades away, the yellow and orange colours finally show through.

• Yellow and orange were hidden

Reds and purples are different, because the leaf makes new red colour in autumn from sugar left in the leaf.

• Red is made fresh

Bright sunny days and cool nights make the reds even stronger, which is why some years look better than others.

Brown comes from leftover waste in the leaf, so it is the dull colour at the very end.

Then the leaf drops off, and the tree rests through winter, saving its energy.

Here is the colour story in order, from a green summer leaf to a fallen autumn leaf.

Quick check: what makes yellow and orange leaves appear in autumn? So leaves change colour because the green fades, hiding colours appear, and some new reds are made.