Flaming autumn

'The summer-flower has run to seed,
And yellow is the woodland bough;
And every leaf of bush and weed
Is tipt with autumn's pencil now.

And I do love the varied hue,
And I do love the browning plain;
And I do love each scene to view,
That's mark'd with beauties of her reign.'

Autumn, from The Village Minstrel by John Clare, goes on for many more verses, but those first two sum up really nicely how I feel about autumn.

Yellow, orange, red, purple, brown

I love this time of year. I love watching the trees turn from green, through oranges and reds, to brown.

Every morning as I come into work, the scene is slightly different from the day before.

But nature doesn't put on this spectacle for us.

Here comes the science

It's in my nature to try and understand things that I see, so if I remember my GCSE Biology correctly, as days get shorter and winter approaches, there is not enough light and water for photosynthesis to take place. Photosynthesis being the process that turns - via sunlight - water and carbon dioxide into oxygen and glucose, which plants use as food to help them grow. This basically means that during winter, trees have to live off the food they've already made.

But how does that explain the amazing range of colours?

It turns out that orange and yellow hues are easy to explain. The pigments that are responsible for these colours were always present in the leaf, but you couldn't see them because they were masked by the green chlorophyll (the chemical that helps make photosynthesis happen). As the tree breaks down the green chlolphyll and redistributes the nutrients to their trunk and roots it exposes these colours.

Red hues, however, aren't so easy to explain. The pigment that makes red has to be made fresh each autumn. But why would trees want to expend energy making this when the leaves are about to fall off? Turns out no-one really knows!

It could be that the red pigment, called anthocyanin, helps trees keep their leaves a bit longer, and therefore they can eek out even more sugars, nitrogen and other valuable food before the leaves fall off. Or, the pigments could protect the leaves from the sun, and lower their freezing point, giving some frost protection. Another possible reason is that when the leaves decay, the anthocyanins seep into the ground and prevent other plant species from growing in the spring - leaving all the nutrients in the soil for the tree.

It's amazing that something that happens every year is still such a mystery! But what isn't a mystery is that autumn creates some truly beautiful colours, and it's definintely a brilliant time to get outdoors.

And it seems I'm not the only one who loves autumn: Mark Avery loves the colours of autumn, Katie talked about it in her recent autumn delights post, while some of our reserve staff are experiencing their first proper autumn! In the US, 'leaf peeping' is big business. People travel from all around the world just to marvel at the mixture of hues that autumn brings

You can experience autumn colours for yourself on many of our reserves.  You can also celebrate autumn by posting your photos on our Flickr group.

Enjoy flaming autumn!