The Science of Fall Folliage

Western Maryland
Originally uploaded by Ewwwww.

It's old news that trees don't 'turn' colours in fall. The green (cholorophyl) just goes away, and the colours that we see (reds, yellows, oranges) were there all along. This much is true. However, beyond that is still not understood.

Current work is showing that the soil that the trees are rooted in makes all the difference. The less nutrients in the soil, the more red the leaves will turn, as the trees try to mine as much energy as it can from the leaves heading into the winter.

So it makes sense that trees of similar colour are usually grouped together, as they share the same type of soil, as illustrated in this wide photo.