Phenology is the study of timing in nature, whether it’s crocuses emerging in the spring, leaves falling from trees, or Canada geese heading south for the winter. And it’s tricky business for fall foliage. The budding of plants each spring is tied almost exclusively to warming temperatures, while fall’s changing colors are linked to cooling temperatures, decreasing sunlight and soil moisture. The brilliant colors associated with fall happen when production of chlorophyll, the green pigment in plants that’s crucial to photosynthesis, slows down as the days get shorter and the nights grow longer. That exposes leaves’ yellow, red and orange pigments that are normally hidden from view. How and when that happens depends on temperatures and moisture levels. In some years, the colors are more vibrant than others. Further complicating matters: A tree that’s stressed may simply drop its leaves, with no color change, or brown leaves.All that to say, autumn is such a beautiful season, let’s take care of the environment to make sure it comes on time every year! 銀座校インストラクター Martin