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What happens in Autumn: Days shorten and get colder, the tree begins to slow. The leaves become less efficient and there is less food for the tree. The oak shuts down, first dropping the acorns and then the leaves. Shutting down takes less energy than fighting the winter. Why does the colour change? Summer leaves are green because they are full of chlorophyll. In autumn chlorophyll production slows and other chemicals in the leaf and the structure of the leaf itself show through. What you see is carotinin - the yellow colour in carrots, cyanothin - the colour in red apple skins and the brown of the leaf . The chlorophyll disappears last from the veins. Why do the leaves fall? Leaves are pushed rather than fall. As the chlorophyll flow slows the tree starts to create a set of cells that separate the leaves from the tree. These push the leaves away and the wind and rain do the rest. As the photos show, leaf fall is fast. Most of the leaves fall within a week - dependant on wind and rain. Some fall earlier others hang on with a few still there in January. Link to relevant part of blog,
Start of photo sequence...Oak Paintings . About the oak tree .. Oak Blog ...Oak Links and books ....Oak home page and movies ..... Mellersh family home page ..Oak Exhibition News . ......Email Nick Mellersh