Where Autumn Colour Really Comes From

A quiet road through a forest in full autumn colour is one of the simplest pictures there is, and one of the most satisfying. The science behind those colours is worth knowing, because it tells you when to go looking.

Yellow and orange were there all along

Through the summer, leaves are packed with green chlorophyll. As days shorten and temperatures fall, trees stop making it and start breaking it down. That uncovers yellow and orange pigments, carotenoids, that were in the leaf the whole time, masked by the green.

Red is made to order

Reds and purples are different. They come from anthocyanins, pigments many trees produce fresh in autumn. Their strength depends on the weather: sunny days and cool (but not freezing) nights tend to give the most vivid reds, while a wet, overcast autumn gives more muted colour.

A leading line

A road or path gives an autumn scene somewhere to go. Letting it curve out of sight under the canopy draws the eye into the frame and hints at what's round the bend. Soft, overcast light keeps the colours rich and even, without harsh shadows.