We all enjoy the colours of autumn leaves. The changing autumn foliage never fails to surprise and delight us. Did you ever wonder how and why an autumn leaf changes colour and why a maple leaf turns bright red? Where do the yellows and oranges come from?

The mixture of red, purple, orange and yellow is the result of chemical processes that take place in the tree as the seasons change from summer to winter.

During the spring and summer. when leaves appear green, it is because they contain an abundance of chlorophyll. Chlorophyll changes energy from the sunlight into food for the plants. There is so much chlorophyll in an active leaf that the green masks other pigment colours. Light regulates chlorophyll production, so as autumn days get shorter and shorter, less chlorophyll is produced. The decomposition rate of chlorophyll remains constant, so the green colour starts to fade from leaves.

As soon as the bright green pigment fades away, other colours revealed and we begin to see yellow, orange, red and purple colours. (Don’t forget that small amounts of these colours have been in the leaves all along. We just can't see them in the summer, because they are covered up by the green chlorophyll.)

Xanthophyl gives leaves their yellow colour.

Carotene gives leaves their orange colour. It also gives the orange colour to a carrot.

Anthocyanin gives leaves their red colour.