Mystified by leaves changing colors?

Like most people, I've always wondered how leaves could change colors in the fall, and while I got the biochemical information I needed about the process itself, I still wondered as to what really made color turn early or late and in a huge variety of colors.

Conventional wisdom puts everything on the back of weather and it might in fact be truer than the chemists would think. For instance, more vivid colors are said to be the result of weather conditions that occur before and during the time the amount of chlorophyll contained in the leaves is diminishing. As most people believe, temperature and moisture are also highly influential.

For instance, a series of warm, sunny days and cool, crisp but not freezing nights seems to bring about the most spectacular color displays. At these moments, large amounts of sugars are produced in the leaf but the cool nights and the gradual closing of veins inside the leaf prevent these sugars from moving out. These combined extreme proportions of sugar and light seem to promote the production of brilliant anthocyanin pigments, which create these reds and crimson colors.

Because carotenoids are always present in leaves, the yellow and gold colors that we get in aspen trees remain fairly constant from year to year. Moisture in the ground also affects autumn colors; that amount varies greatly from year to year.

The myriad of combinations of these two factors assure that no two fall seasons are exactly the same. A late spring, or a severe summer drought, can delay the start of fall color by a few weeks. A warm period during fall might also dim the intensity of the colors. Now remember this: A warm, wet spring, a good summer and a warm sunny fall with cool nights should produce the most spectacular autumn colors.

 Time for me to go out an shoot some more pictures!