By Philip Eden
Autumn used to be my least favourite season. Then one year, while working in the Middle East, I returned home for some leave towards the end of October. The drive home from Heathrow was a revelation: the brilliant autumn colours set against a crystal clear blue sky, the early-morning sunshine slanting brightly through the trees. Why had I never noticed this before?
It was, perhaps, an illustration of the truism that you have to be deprived of something to appreciate it properly. After months in the desert, the sky white, the sun glaring, the ubiquitous sand a dreary dun, nearly all colour bled out of the environment, the sudden change to late-October in England could hardly have provided a greater contrast. Ever since, I have looked forward to these few weeks when the autumn colours are at there best.
Where do these autumn hues come from? The fact is that a variety of pigments, including greens, yellows and reds, are present during the spring and summer, but the greens are so dominant that they completely mask the other colours. This is the result of chlorophyll production which is essential to the conversion of carbon dioxide and water into the nutrients necessary for the trees to grow. In autumn the process ceases, the chlorophyll in the leaves breaks down, the green pigments disappear, and the other colours become dominant. The change is triggered by the progressive drop in light-levels, and in particular by the shortening daylength. The temperature of a particular season may accelerate or delay the process by a few weeks and a warm autumn, as in 1978 or 1994, may see the autumn colours last until mid or late-November.
To my eyes, at least in my neck of woods, autumn 2000 has been a very average season for colour. And in any case our autumn tints are bland compared with those found in Canada and the USA. They, of course, have developed a tourist industry around what they call the "fall foliage season"; New England is probably the best region to visit but the shortness of the season guarantees high prices.
The best colours occur during cool sunny autumns with little rain and light winds, and without severe frosts. The best recent year in the UK was probably 1996. The leaves are still alive at this stage, but a hard frost will cause the supply of nutrients to the foliage to cease and the leaves will drop almost immediately. The displays are more dramatic in North America, not because of climatic differences, but because of the different trees which are native to the area. Many maples produce stunning scarlets and crimsons, as do some American oaks, hornbeam, some laurels, sorrel, sassafras, tupelo and sumach. White ash and wych hazel are known for their purple and maroon tints. In the UK our most startling colours are seen on introduced species.
© Philip Eden