Falling for fall

What makes a Lowcountry autumn special to you? Is it the cooler weather, the lower humidity, or swatting at fewer mosquitos?  

 

Fall is this writer’s favorite season, and he would probably put college football, oyster roasts and the changing of the leaves down as the top reasons why. That first autumn day when one can wear a sweatshirt all day long and not actually sweat is the finest weather day of the year!

 

Some things are so “natural” and so predictable that we simply take them for granted. When autumn comes, the leaves on many of our trees change color and fall to the ground. It’s like the sun rising in the east and setting in the west. We don’t really even wonder why. But the science behind “fall” is interesting, if not fascinating, and

a little insight into why things happen the way they do may generate a little more appreciation for this annual season of change.

 

One surprising fact is that, while things like temperature and moisture can affect the brilliance and hue of fall foliage, the main driver of when fall begins is simply the amount of daylight per 24 hours. Early cold snaps, rains, droughts, etc., don’t affect the timing of fall nearly as much as how much light plants get each day.

 

It is also interesting that most of that brilliant fall color that ultimately adorns our autumn leaves before they drop has been there all along. It has just been overshadowed. During the spring and summer, trees are working furiously to grow, to compete for sunlight, and to get prepared for the next fall and winter. Chlorophyll is the

substance plants use for photosynthesis, or the process of absorbing light, making food and releasing oxygen. Chlorophyll is a robust green in color and when it is at work most other leaf colors are covered up and undetectable.

 

As the days get shorter, plants prepare for winter. The veins and midrib (the large central vein feeding the plant) shut down and close off. Chlorophyll begins to disappear, revealing whatever natural colors the particular leaf has. 

 

Carotenoids are pigments found in most leaves, and they produce the oranges and yellows common on most trees. Anthocyanin is a pigment associated with residual sugars remaining in some leaves, and it generates the vibrant reds and purples that really fire up our fall foliage. Some trees, like elms, have little natural leaf color.

Their leaves simply fade to a dull, woody brown and fall to the earth.

 

This amazing planet of ours is full of complexities we seldom consider. But whether or not one spends much time thinking about why a leaf was a certain color or why it fell off of the tree when it did, fall and its colors seem to delight nearly everyone. So don your favorite sweatshirt and head outside for a walk. The beauty of what

you’ll see outside this month will likely eclipse anything you miss on the television or computer screen.