Autumn leaves (photo: Keith Huggett)
The colours of autumn
Kate Lewthwaite, Woodland Trust
Kate Lewthwaite of the Woodland Trust talks about autumn colour and why our trees change colour at this time of year.
Autumn is nature’s way of treating us to one last burst of colour before the winter cold sets in. Trees across the UK are now going into full colour creating displays of wonderful yellow, gold and red shimmering leaves for all ‘leaf peepers’ to see. As summer turns into autumn, the shorter days and cooler nights trigger changes in the leaf to prepare it for leaf drop, and as a side-effect, change its colour.
Autumn woodlands (Photo: Ilene Sterns)
But why does this happen?
Lower light levels stop production of chlorophyll - the green pigment in leaves which captures sunlight energy. The tree uses chlorophyll to convert carbon dioxide and water into sugars and oxygen. The tree uses sugars for food.
A yellow pigment, carotene, also has a role in photosynthesis and has been present in the leaves all summer but is usually masked by green chlorophyll in the leaves. As the green chlorophyll fades, yellow carotene is the colour that's left behind, making the leaves yellow.
When autumn days are sunny and dry, sugars trapped in the leaf - leftovers from when the tree was photosynthesising to make its own food - become concentrated in the leaf and can produce a further pigment known as anthocyanin,which is red/purple, giving a further range of glorious colours.
Weather conditions also have an effect
In a normal British autumn with plenty of rain we expect to see classic yellows and golds as carotene in leaves is revealed and the trees prepare to shed their leaves. When autumnal weather is sunny, warm and dry (our “Indian summers”) anthocyanin production in the leaves may occur, giving us a North American type autumn with yellows and golds supplemented by deep reds and purples.
Autumn colour (Photo: Nick Spurling)
For the greatest variety and intensity of autumn colours, sunny, dry autumn days with cold but not freezing nights are best, especially if preceded by a dry summer.
People all across the world from Japan and the USA flock to see the autumn spectacle, and we’ve got our own on our doorstep. The best place to see autumn colour in Essex is at Hainault Forest near Romford - owned by the Woodland Trust – has wonderful colour. But be quick it won't be long before we're kicking through piles of fallen leaves.
To find you nearest Woodland Trust Wood visit www.woodland-trust.org.uk and follow the woods link
last updated: 13/11/07