Fall is a season of change, and changing weather --mild days, cooler nights, sharp blue skies, the glorious colored leaves.
Why do leaves change color in the fall?
The green of summer leaves is the result of an abundance of chlorophyll. In an active leaf, the chlorophyll masks the other pigment colors. But as days grow shorter in the fall, chlorophyll production diminishes. The green fades, revealing the underlying colors in the leaves.
Carotenoids produce the yellow and orange colors in leaves and also appear in peppers, corn, carrots, daffodils, buttercups, and bananas.
Carotenoid production is not dependent on light, so levels aren't diminished by shorter days.
Yellow leaves are characteristic of sycamore, birch, ash, hickory, yellow poplar, some oaks and maples, and many other trees.
They are found in the reds of sugar maples and red maples, sumac, oak trees, dogwoods, and many other woody plants.
Tannins are the browns in the leaves of some oaks and other trees. They are always present, but only become visible as chlorophyll and carotenoids disappear. Tannins are also what gives tea its color and flavor.
How does weather affect the intensity of leaf colors?
Anthocyanins are dependent on light and temperature. Sugars remaining in the leaves on warm sunny days and cool nights increase anthocyanin production, creating the most intense reds.
Rainy and/or overcast days decrease anthocyanin production, resulting in more yellows and browns.
The amount of moisture in the soil also affects leaves. A severe summer drought can delay the onset of fall colors.
A wet spring, normal summer rainfall, and warm and sunny fall days with cool nights are the ideal conditions for the most spectacular fall colors!