Why do leaves change colour in Autumn?

Autumn colours Credit: @TractorWalking on Twitter

Autumn - its arguably the most colourful season. As we leave the warm summer days behind and head into the autumn months, the natural colour pallet changes across the landscape. The trees swap their lush green leaves for burnt orange, deep purples and rich reds. But why does this happen and can the weather impact which colours are displayed?

Autumn leaves and sunshine Credit: @TheSuffolkMan

Tree leaves are green due to a chemical within the leaves known as Chlorophyll, which is vital for tree growth as it turns sunlight into food. Interestingly the colours that we associate with Autumn are always there in Summer, but as the chemical Chlorophyll is so intense, the leaves appear green.

As the weather begins to cool and the days start to draw in after the equinox, the trees sense this and begin the yearly process of shutting down for winter. The nutrients stored within the leaves are sucked back into the trunk, later to be released in spring to start the new growth. As a result, the chlorophyll begins to break down, allowing the array of autumn colours to be displayed.

Leaves changing colour Credit: @TractorWalking on Twitter

Sunny Autumn days break down the Chlorophyll more quickly, whereas cool chilly nights encourage more red and purples to develop. Meanwhile, frost and drought make the leaves drop more quickly whilst strong winds and autumn storms pluck the leaves from the trees before they’ve had time to change colour.

So what weather would give the perfect display of autumn colours?Ideally, warm wet spring will help to encourage new growth, followed by a sunny summer superseded by warm sunny autumn days and cool chilly autumn nights.

Autumn trees Credit: Cliff Salt