Fall Leaves

Now that it's fall, I'm noticing a lot of questions about the leaves. Namely, what makes the colors change and why do trees lose their leaves?


Inside the leaves of trees are many phytochemicals. Most of the year, green chlorophyll is the most prominent one. But there are others, and these come in many colors! They are actually always there, but in the main growing season, they are simply drowned out by the chlorophyll.

When the weather cools and days shorten, the chlorophyll begins to break down as the tree starts to enter dormancy. This is what causes the change in color. Once the chlorophyll isn't covering up the colors of the other phytochemicals (natural plant chemicals), they shine out, sometimes with great beauty! How beautiful? That depends on what species of tree, and on the weather. Rainfall, or lack of it (depending on which weatherman is talking) can cause the other colors to end up kind of drab. I personally notice that the display is lackluster if there has been a lot of drizzle and humidity.


Between each leaf's stem and the woody stalk it is attached to, is what is called an ABCISSION LAYER. This is a barrier of cells. During the main growing season, this functions like part of the leaf stem, allowing nutrients and water to pass much like the stem itself. But, in response to the same changes that trigger the change in leaf color, the cells of the abcission layer begin to die. When most of them are dead, they can no longer hold the leaf to the tree, and it falls. This layer is what you see when you look at the place where the leaf just fell from in the fall. You will see a shape on the woody stem (where the leaf was) which is the shape of the end of the leaf stalk. This "leaf scar" is what's left of the abcission layer. The layer's continued presence on the tree helps to keep infection from the tree by preventing an open wound from resulting from the leaf's fall. It's like an immediate, natural band-aid.


HA! HA! Just joking! Give 'em a few passes with the mower and they'll go away, no work at all if you have a riding mower, and even if you don't, it beats raking!!!

ENJOY the colors!


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