It’s peak leaf-turning time all over the Northern Hemisphere. Here are five of our favourite leafy destinations in Europe, plus a little bit of the science behind changing leaf colour.
1. The Picos de Europa National Park in northern Spain
2. The rolling hills of Tuscany in Italy
3. The beech tree covered Chilterns, in the UK
4. The French Alps in autumn are prefect for hiking before the snows come
5. The countryside near Munich in Bavaria, Germany
What makes leaves turn from green to yellow, red and orange?
Leaves are little “food factories” full of a compound called chlorophyll, which gives leaves their green colour in spring and summer. The leaves also contain carotenoids (the chemicals that gives carrots their orange colour). During the spring and summer the chlorophyll’s green colour masks the orange carotenoids, and so we see green leaves.
At the onset of autumn, with its shorter days and cooler temperatures, the leaves slow down and eventually stop their food-making process and no longer need the chlorophyll. It begins to break down, allowing the orange carotenoids to shine through.
The late summer-early autumn weather also affects another group of chemicals in the leaves called anthocyanins. This is the group that makes plums and red grapes red. The bright, warm weather during typical September days stimulates leaves to produce lots of sugar, but the cooler September nights inhibits the trees from using it. That leads to a build-up of sugars in the leaves, which triggers anthocyanin production, which in turn produces the impressive array of red colours.