What Causes the Leaves to Fall?
What causes the leaves to fall? The answer isn’t as simple as the leaves change colors. There are a lot of processes going on in the tree.
The Changing Colors of the Leaves
In the autumn, days become shorter, and nights become longer. It is not the shorter days that affect the trees as much as it is, the longer nights. When the darkness increases, the leaves slow down their production of chlorophyll.
What is Chlorophyll?
Chlorophyll is the pigment in the leaves that makes them green. It is located inside the cells in the leaves and is responsible for absorbing energy from the sun. This energy is then broken down during photosynthesis to make food for the tree.
What Happens When Chlorophyll Slows Down?
The longer nights signal the tree to decrease its production of chlorophyll. The increase in darkness and decrease in sunlight tells the tree that winter is coming. When the chlorophyll production slows down, the colors (carotenoids) underneath the chlorophyll are visible. The oranges and yellows of the leaves are now coming through.
Try this neat experiment to see the colors lurking behind the green in the leaves.
Where Do Red Leaves Come From?
Red leaves come from a pigment called anthocyanins. Sunny days and cold nights aid in the production of anthocyanins in the leaves of trees. During sunny days, the leaves make sugars. When the cold nights hit, the sugars can not go into the tree. They stay in the leaves. These sugars cause the red pigment you see in the leaves.
Why Do Leaves Fall From the Tree?
Just as autumn’s shorter days and longer nights tell the tree to stop chlorophyll production, it also signals that it is time to release its leaves. The tree forms a layer of cells that sever the tissues which hold the leaves to the stem. The tree also heals the spot where the leaf and the stem connect. When the leaf finally falls from the tree, a leaf scar will remain.
Why are Some Autumns Better Than Others?
Weather, not only during the autumn months but also during the summer, affects the brilliance of fall foliage. Summers with dry conditions stress trees, causing them to turn brown and lose their leaves early.
On the flip side, adequate rainfall in the summer aid in keeping trees healthy, producing excellent fall color. Early frosts and rainy and windy days will also cause leaves to turn brown and fall from the tree prematurely. Sunny, cold days produce the best colors in the fall.
Now when fall rolls around, and you ponder, “What causes leaves to fall?” You will know the answer.
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What Causes Leaves to Fall?
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I’ve always loved gardening and recently started gardening full-time. I also enjoy tending to our chickens, dogs, and other family pets (a bird, a snake, and rabbits).