Updated: Nov 17, 2019
Recent years have been characterised by particularly vivid autumn colours and there are a number of reasons why our trees have provided such wonderful displays. Some of these reasons are climatic; this year weather patterns of preceding months – particularly the delayed spring (remember the Beast from the East?) and long, dry summer – have been conducive to this splash of colour. More generally, warmer autumns have persuaded trees to retain their leave just that little bit longer. In some cases, this has occurred at different rates meaning that trees, which normally lose their leaves at different times, are now doing so almost simultaneously. This makes for an explosion of colour.
Climatic conditions also influence the vividness of autumn leaf colours. Once the leaves have gained their leaves in the spring, they start to store carbohydrates that are required for growth the following year. Chlorophyll is the chemical that give the leaves their green colour; it is constantly replaced throughout the growing season. As the autumn nights increase in length, cells divide in such a way so as to eventually block the supply of chlorophyll to the leaves. The lack of chlorophyll allows for yellow, orange and red pigmentation to become visible (the amount of each of these depends on the species of tree). It is this pigmentation that is responsible for leaves changing colour in autumn. Our late and short spring followed by a long hot summer – ideal for vigorous tree growth – was succeeded by mild (and, largely, sunny) conditions in early autumn – perfect for the development of colourful pigments. These mild conditions have persisted with the result that leaves have been able to produce their vibrant pigmentation unhindered by much in the way of overnight frost. Freezing temperatures prevent this process from occurring – thus, an autumn with early frosts is unlikely to be an exceptionally colourful one. The forecast cooler breezier conditions are likely to put an end to this explosion of colour. Enjoy it while you can!