As Autumn approaches the days shorten and the temperature begins to drop. To survive the next season, every year the deciduous trees transform themselves and a dramatic process unfolds. Hormones are produced by the trees to prepare themselves for Autumn and they drive the process of breaking down the pigments and nutrients in the leaves to store over the Winter. Trees undertake a colossal redistribution of their resources and as Autumn takes hold a hubbub of chemical messages are sent through their branches. They sense the impending change.
Oak, beech and ash predominate at Ashridge, whilst the oak remains the icon of the British countryside. The Estate supports many veteran oaks, and some ancient specimens. The hormonal changes taking place throughout the trees means in effect that they begin to eat themselves. The result is a spectacular change in the colour of the leaves. Once the pigment chlorophyll is taken out, the green leaf colours turn to a palette of reds and yellow. With the nutrients extracted the trees will then shed their leaves to conserve water and energy. The pigment phytochrome will have measured the hours of sunlight and darkness and acting like a chemical stop-watch, it kick-starts the autumnal process.
Not only will trees shed their leaves in Autumn, but they also release their offspring to the outside world – in the case of the oak it is the acorn. Inside this little capsule is not only the genetic code to produce an ancient oak, but it is packed with food and protection from the elements, to survive the Winter. The trees rely on the work of jays and squirrels to spread their seed, as these little helpers often plant them underground and then forget where they are hidden! Acorns are a masterpiece of evolution. The oak like the beech has an ingenious trick to improve the seeds’ chance of survival as it varies the number of seeds it produces from year to year. In some years there are just a few, and in other years there are thousands – a mast year. This means that the jays and squirrels cannot rely solely on acorns and must find other food to survive. A mast year produces so many fruits that the little helpers cannot cope with the volume so some acorns will germinate the following year. That’s nature for you!