The Science Behind Autumn Leaves Changing Color Explained!

Autumn is known for transforming deciduous trees into magnificent displays of red, yellow, and orange leaves. Unlike evergreens which can endure cold climates because of their foliage’s thick wax coating and the freeze resistant substance within allowing them to hold onto their leaves, deciduous trees have their own way of adjusting to changes in climate.  The leaves of a deciduous tree changes color and eventually falls off, but there is more happening than a change in appearance.  To understand the science behind the change in color of autumn trees, it is important to take a look inside the leaves of a deciduous tree.

The colors of red, yellow, and orange in the leaves of deciduous trees are the result of organic pigments known as carotenoids and anthocyanins.  Carotenoids, a pigment present in the chloroplasts within the cells of leaves, results in the yellow, orange, and even brown shades.  Anthocyanins are produced through exposure to bright light and excess plant sugars in the leaves and they are responsible for the various tones of red in a leaf. During the spring and summer, chlorophyll, which is found in every plant, masks these other pigments with its green color.  Chlorophyll is an important part of photosynthesis, a chemical reaction in the plant that converts energy from sunlight into chemical energy and is essential for plant life.

In autumn, when the nights tend to become longer and colder, deciduous trees senses this change and begin to prepare for the upcoming winter by slowing down and eventually stopping the production of chlorophyll in it's leaves. The absence of chlorophyll exposes the carotenoids and anthocyanins, making the autumn colors of the other pigments visible!  When the chlorophyll is all gone, the tree is able to rid itself of its leaves. This is important because otherwise the leaves would freeze and the tree would not survive.

The changing colors and dropping of the deciduous tree's leaves is key to it making it through the winter.  Without chlorophyll to hide the other pigments, the traditional autumn colors of red, yellow, and orange can be easily seen.  This change in color is not only a beautiful sight, but also a process that has more to it than meets the eye!