London is currently in the cradle of autumn. My cycle to work is flecked with crispy leaves and in polite conversations people find comfort in talking about how it’s ‘suddenly got colder’.
Some trees succumb to the cold faster than others and have already bloomed into a rainbow of reds, oranges, pinks and yellows. Some are more eager to hold onto their youthful green leaves. The chaotic mix of different colours creates a lovely dappled effect, a bit like one of Georges Seurat’s paintings.
This spectacular change of colour happens when a pigment called chlorophyll (which makes leaves green) starts to break-down and is reabsorbed by the rest of the tree. The tree sucks the nitrogen out of the chlorophyll and the remaining nutrients are stored as a winter fat reserve so the tree has enough energy to jump into action the following spring.
The autumnal tints are thanks to the presence of other pigments called carotenoids and flavonoids that become more prominent in the leaf. Chlorophyll absorbs red and blue light meaning it reflects green but these pigments absorb different colours, meaning the tree reflects yellow and orange hues. Different temperatures favour different pigments so every autumn creates its own jostle of colours.
Email me your autumnal pictures or tweet them with #rewildinglondon. Here are a few of mine from this week.