Arborist Explains Why Trees Shed Their Leaves in the Fall
Fall is a favorite season for many people. The cool dry air is a welcome relief from summer\’s heat and mugginess. At some point, nature seems to show off with a brilliant display of brightly colored foliage that only the blossoms of spring can match in beauty. Then sadly, the color fades and the leaves drop from the trees. However, this process seems like an extravagant waste. Why not keep the leaves throughout the winter so that they don\’t have to be regrown again in the spring? Why do deciduous (broad-leafed) trees do this?
One reason is that the freezing cold of winter would damage the broad leaves and prevent them from producing \”food\” for the tree from sunlight and carbon dioxide (via photosynthesis). Another reason is that the days are shorter and the sun is lower in the sky during the winter. This means the leaves get little sunlight and can\’t produce much food for the tree in any case.
Rather than hang on to dying and dead leaves during a time of year when there isn\’t much food-producing sunlight, trees cut off their leaves by growing abscission cells at the point where the leaf stem meets the branch. As these cells grow, they separate the leaf stem from the branch. At some point, a bit of wind does the rest of the job of getting rid of the leaf. By the time the leaf falls off, a protective layer of cells has grown over the exposed area.
Signs of Autumn
This entire process starts when the shorter days and colder temperatures of fall trigger a hormone that causes the abscission cell growth.
Note that the tree doesn\’t wait until the leaf dies because this dead tissue would provide an avenue for disease to take hold. It\’s a kind of preemptive self amputation. During this process, chlorophyll production stops. The absence of green colored chlorophyll leaves the other brightly colored pigments behind, which is the reason for the foliage colors of fall. The tree then hibernates during the winter until the spring.
If you require pruning or tree removal or have tree health problems, an arborist from Advanced Tree Care can help. You can follow along on Facebook and Instagram, or you can contact us here if you have any questions.
