The days are growing shorter and New England comes alive with color. Why such great color here? The answer lies in our mixed deciduous hardwood forests and our climate. First - Why Color? Leaves are the food factory of a plant. During the summer the leaf's green chlorophylls are working hard to produce food for the plant's survival. They are so abundant, they mask out the other pigments in the leaf. But chlorophylls are very unstable and they must be constantly replaced. As the sunlight diminishes, they are replaced at a slower and slower pace. Eventually the other pigments called caroteniods start to become unmasked. These appear yellow or orange or many hues in-between. The birch or beech trees have an abundance of these.
As time progresses less water and nutrients can enter or exit the leaf. This causes a backlog of chemicals. In some plants, these trapped chemicals, plus light causes anthocyanins to form. These create the reds and purples. The brighter the light during this period, the greater number of anthocyanins are produced and the brighter the color. Some plants like sumacs have so much anthocyanins that they mask the caroteniods completely. While others like the sugar maple slowly produce it so that their leaves first turn yellow, orange then red. But some like the birch can't produce it at all.
Dry sunny days followed by cool dry nights enable the above processes to create the brightest colors. The best variety of color comes from hardwood deciduous forests which contain a wide assortment of trees. New England's climate and forests meet both requirements for world class fall foliage.