by Johnny Caryopsis People don't think much about leaves until autumn. Then, for a brief time, we revel in the multitude of colours that emerge from what was previously a plain green background. Of course, there were subtleties of shade and texture in the greenery that surrounded us all summer, but after the first flush of green in the spring, we quickly grow accustomed to the green backdrop of plant leaves and focus our attention elsewhere. The coming flowers or ripening fruits seem to be all that we care about, however small these components may be when compared to the entire, leafy plant. We often see leaves only as a background to set off the more attractive parts of plants. But when days shorten and grow crisper, leaves come into their own, though it is only in death that they finally attract our attention. As the golds, yellows, reds and browns of autumn emerge we come to realize the diversity of the plants that once made up the summer greenery. Where many different plants or trees grow together, the green background is transformed into a mosaic of individual plants in varying hues. Plants often turn colour "out-of-sync" with their neighbours so that even in single species plantings, they stand apart from the others. For a few short weeks before winter's white coat arrives, Mother Nature shrugs off her dowdy greens, throws fashion sense to the wind and bursts forth with a season ending explosion of colour. And then we get out the rakes! But what is the cause of our fall splendour you ask? Where do the yellows, golds, reds and browns come from? The complete answers to these questions involves some pretty hefty science, with lots of plant biochemistry and physiology. I don't pretend to fully understand the myriad of processes involved, but I think I've got enough of a handle on it to help you grasp it, too. But, just in case you're in a hurry, and want it in a nutshell, here's what happens. Fall colours explained in under 100 words: As plant leaves begin to die in autumn the green photosynthetic pigment, chlorophyll, decays rapidly while other photosynthetic pigments, yellow carotenoids, decay more slowly and still other pigments, red anthocyanins, are produced as byproducts of the death of the leaves. The green colour fades to reveal the underlying yellows, reds and browns (from tannin and other compounds). The exact colour and vibrancy that develops are influenced by plant genetics and the environment. For a little more information, please read on.