The Science of Fall Foliage: An Exploration of Why Leaves Change Colors

As the days grow shorter and the temperatures start to drop, the leaves will begin to burst with color. The yellow, orange, gold and red hues will awe us as the trees and shrubs prepare for winter. Some of us may wonder why the leaves change color. This article will explore this topic, using science to explain the phenomenon of fall foliage.

The Importance of Weather and Biology

Weather and biology play two important parts in the scientific explanation of the changing colors. Weather has a strong impact on the foliage season. For the best, most timely colors, a warm and wet spring is desired. As autumn approaches, warms days and cool nights are needed conditions to produce the most vibrant colors. Temperatures below freezing and frost make for delayed changes, and less bright colors.

Biology is perhaps the most important part in determining fall foliage. Basic biology reminds us that plants use photosynthesis to make food for themselves. Leaves change sunlight into energy. Plants use both chlorophyll and carotenids to absorb light. Yet, green light is not absorbed or is reflected by chlorophyll, resulting in leaves appearing green. As fall approaches and the amount of sunlight decreases, plants begin to slow their production of chlorophyll, eventually stopping it altogether. When chlorophyll is not produced, the other pigments in the leaves appear. Pigments such as anthocyanins create blue, red and violet color. Tannins appear brown. Carontenoids and Carotenes make leaves turn orange and yellow. Xanthophyllis also creates a yellow hue. The result is the appearance of leaves changing color, which should actually be considered leaves losing color in the fall.

The Fall Foliage Season

For the most part, fall foliage begins to show itself in September, starting in the more northern areas. Websites like the Foliage Network allow viewers to see where the colors are the brightest or the best, using local “spotters” to find the optimum fall foliage. The Foliage Network covers the areas of the Northeast, Southeast and Midwest United States. The information is then passed on the television stations and newspapers. During autumn months, The Weather Channel also has information and regional maps online and on the air of peak, past peak, near peak and patchy fall foliage.

Plan a fall foliage excursion, taking a day trip to spot the autumn colors. Use maps, online resources and travel books to map out your route, letting you explore the surrounding hills and mountains during the early autumn months. Fall foliage first appears in the more northern areas and higher elevations.