If you live in the north then you already know why Fall is a fantastic time of year. First and foremost, the cooler temperatures are bearable with little extra clothing cover up, such as a sweater and pants, and the air conditioning can be placed into hibernation. Among other advantages this gives temporary reprieve from those ghastly air temperature control costs before the heat is switched on for winter. If you have children, then they are likely back to school and the residence probably collects on its serenity for a few extra hours per day.
But one of the absolute best parts of fall is the sight-seeing. Whether you are driving down a country road or engaging in an outdoor activity, nothing beats the aesthetic appeal of leaves vacating their greenery and electing to give us a dazzling spectacle of rustic nature. While we often take in this seasonal change with little afterthought, every once in a while our curiosity beseeches us with the question, “Why do leaves change colors?”
It is first imperative to understand why trees need leaves. Trees, like other plants, feed their growth through the same photosynthesis process that gives the green color to various vegetation. This, as many are familiar with, is the process of turning water and carbon dioxide into sugar by using sunlight.
While various vegetation does reflect a greenish hue, there are actually three main natural substances called pigments that make up leaf colors. The first, and the most important, is chlorophyll. This is the dominant pigment and is the primary director of sunlight to create a tree’s sustenance. The second, which create yellow and orange, is the carotenoid. These can be seen in fruits and vegetables like corn, bananas, carrots, and many others. The final pigment is called anthocyanin. This produces a rosy tint and colors red apples, strawberries, and red peppers.
Next we need to understand the cycle of the earth. At this point it follows common knowledge. As the northern hemispheres tilt away from sunlight, trees are finishing their summer supper and are preparing for the long winter ahead. When the hours of sunlight in a day begin to decrease, trees will diminish in their supply of chlorophyll, thus losing the rich greens we have grown accustomed to viewing the past few months.
When these greens retreat does that mean carotenoid begins its production process? Actually no. Carotenoid has been prevalent in the leaves the entire time, but because chlorophyll is a stronger pigment and much more vital to the growth process, it trumps those glorious yellows and oranges we see only in fall-time.
That leaves the final pigment, anthocyanins. These typically are created in the final days of a leaf’s life cycle. During nights where the temperatures drop too deep, sugar sap cannot efficiently flow from the stems to the trunk of the tree. Therefore anthocyanins step in and make that final squeeze, fueling the tree just enough to make it through the impending cold spell.
The final process is for the leaves to detach from the leaf stem and give us one last astounding dancing spiral to its final resting spot on the ground below the tree. A special layer of cells will develop to make this severance, and a leaf scar will mar the tree.
There are factors that affect the appearance of colors in a tree during autumn. For example, a drought can delay the coloring process or an early frost can kill leaves overnight. Research shows that when we have a warm, wet spring, an average summer that is not too hot or dry, and a dry fall with clear skies, we will see the most beautiful and abundant coloration in the fall.
Of course, the type of tree plays a part also. Oaks tend to be red or brown, birch will showcase a vivid yellow, and maple trees tend to vary across the spectrum. Don’t forget there are also evergreens such as pines, spruces, and firs that defy the odds, but nonetheless whether the tree is young or old, an oak or a hemlock, or the summer is too wet, or a frost sets in too early, we can always rely on catching some spectrum of beauty spread across the region every autumn.
