The best fall colors are produced by warm, sunny days and cool but not freezing nights. |
Why Do Leaves Change Color?
Decidious trees have a chemical clock which tells them when days get shorter and nights longer. This is a sure sign that it's time to prepare for winter weather and alter their leaves.
How do they do it?
Leaves have several types of pigments (chemicals in charge of color). The one we are most familiar with is chlorophyll, which makes the green color we see in leaves all spring and summer. It's also responsible for photosynthesis (turning sunlight, water, and carbon dioxide into sugars that feed the tree). In the fall, trees shut down and stops making chlorophyll. As the chlorophyll disappears, another pigment in the leaves become visible: carotenoids. These pigments make the yellows, oranges and browns that we see in sugar maple, aspen, birch, and ash trees.
In late summer, some trees also produce pigments called anthocyanins in their leaves. These combine with the carotenoids and create the bright fiery reds and oranges of red maple, oak, sumac, and dogwood trees.
Why do leaves fall?
As cool weather approaches, a special layer of cells called the abscision layer forms between the leaves and where they attach to the branch. The abscision layer seperates the leaf from the branch and allows it to fall. Oak and beech trees are an exception: their leaves often stay on the tree throughout winter.
Learn more: Why Leaves Change Color
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