Pigeon Forge truly is a remarkable place. Sitting on the outskirts of the Great Smoky Mountain National Park has given the area an incredible backdrop. During fall, that backdrop changes to stunning colors of red, yellow, orange and brown. The changing of the leaves is one of nature’s largest events in the area and draws in a multitude of visitors.
When do the leaves make the transition to the new colors?
It depends on many factors. For the most part, the leaves should be in full changing mode by the second week of October. Some years it may come earlier or later, depending on rainfall, temperature and other natural elements.
How and why do the leaves begin to change colors?
When the days begin to grow shorter and the air grows cooler, the trees reduce the amount of photosynthesis they are willing to do. This causes a reduced level of chlorophyll which is the green pigment in leaves. Chlorophyll works by absorbing sunlight and using it for photosynthesis. Since the tree is not requiring as much of the photosynthesis process, chlorophyll begins to deplete.
During spring and summer, chlorophyll masks the yellow and orange pigments (carotene and xanthophyll). Once fall arrives and the chlorophyll begins to dissipate, the other colors are no longer masked and become highly visible.
The red color comes from anthocyanin. While carotene and xanthophyll are present in the leaves year round, anthocyanin does not appear until the chlorophyll begins to break down and the plant will then synthesize anthocyanin. Anthocyanins are believed to help protect the plant from sun damage, lower the plant’s freezing point, and help keep the leaves on the tree longer which allows the plant to absorb more nutrients from the leaves. The shades and hues of the reds in a tree is based on the pH of the leaves’ cell sap. If a leaf has acidic sap, the leaf will yield a bright red color. If the leaf is more basic and less acidic, the red tends to be more purple in color.
Leaves are likely to have more reds if the weather is sunny during the day with cool nights. If the weather is cloudy, yellows and oranges are more prevalent. This is because the anthocyanin production is not as necessary to protect the leaves from the sun.
Brown is the least exciting part of the transformation. The brown colors come from the waste products that become trapped within the leaf.
The leaves will fall when the veins that transport the nutrients and water to the leaf from the rest of the tree are sealed off.
