Keats called this time of year the `season of mists and mellow fruitfulness.’ Whilst we have only had a few mists and fogs so far, the lack of the usual October strong winds means that many leaves are still on the trees. As the days shorten and the trees close down their food production systems, the reduction in the chlorophyll in the leaves is leading to the beautiful colours this Autumn. The reds, ambers and yellows are due to the chemicals Carotenoids, Flavonoids and Anthcyanins. A recent study suggested that the red colour is intended to stop aphids attacking certain trees, as the yellow colour is attractive to sap sucking insects. The leaves fall as a layer where the tree meets the leaf, called the abscission zone, swells. This slows the transport of nutrients from the tree to the leaf. Once this zone is locked, a tear line forms and grows downwards, until the leaf is blown away or falls off.