Why Leaves Change Colour in Autumn

Vocabulary and key concepts explaining the chemical and biological processes behind why leaves change colour in autumn.

Chlorophyll

The substance that keeps a leaf green all summer and hides every other colour inside the leaf until shorter autumn days cause production to stop.

Yellow and orange (in leaves)

Colours that were always present inside the leaf and finally show when chlorophyll production stops and the green fades.

Red pigment

A newly formed pigment created on cold, bright autumn days when the leaf makes sugar faster than it can transport it away, converting the trapped sugar into colour.

"Autumn is a subtraction, then a single new line"

A phrase describing the process of leaf colour change: first losing green to reveal existing yellow and orange pigments (subtraction), followed by the creation of new red pigment.