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The colour of autumn

Brett Westwood

Naturalist and broadcaster

Image by Colin Dixon

Across the UK in our parks, gardens and woodlands, trees are glowing in their brilliant autumn colours. The green chlorophyll pigments, which help the leaves produce sugars from sunlight, break down to reveal a dazzling rainbow of yellows, oranges, reds and russets.

Image by Kez West

Some of our commonest trees such as beech, birch and field maple produce bright yellow leaves in autumn. The yellow colour comes from carotenoids which help the tree to capture sunlight and protect leaves from antioxidants. We see it in autumn when the green chlorophyll breaks down.

Image by Della Lack

Red colours are made by anthocyanins which the tree produces in autumn. Rowans often have red or bright orange leaves, but the brightest scarlets and crimsons are made by Canadian and Japanese maples which burst into flame in parks and gardens.

Image by Brett Westwood

Green patches of chlorophyll in autumn leaves often surround the mines of insects which tunnel between the top and bottom layers of the leaf. The chlorophyll is kept nourished by the insects' waste products while the rest of the leaf turns colour. This beech leaf contains the squiggly mines of a tiny moth larva.

Image by Simon Dell

Scientists now believe that autumn colours are produced to protect the tree foliage from intense light as the green chlorophyll breaks down. Anthocyanins produce brighter red pigments in leaves that are more brightly lit than shaded ones. Areas with cold sunny autumns such as North America have many more species of red-leaved trees.

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