Autumn is upon us once again! To celebrate, we’re exploring the science behind our favorite fall foliage.

To understand what causes leaves to change color, we must first discuss what makes them green in the first place! Inside leaf cells, there is something called chloroplasts. Chloroplasts produce food for the leaves and serve as a place for photosynthesis to happen. Chloroplasts collect light energy from the sun and use photosynthesis to convert it into chemical energy. Chloroplasts use the captured sunlight to convert carbon dioxide and water into oxygen and sugars. The chemical energy that was created through photosynthesis is then stored in the sugars. This is the force that allows plants to grow and reproduce.

But what is it that determines the colors of leaves?

A pigment called chlorophyll absorbs sunlight to give leaves their green color. In the spring and summer months, chlorophyll overpowers all the other pigments contained within leaves cells. However, chlorophyll requires sunlight and warmth to produce the green color. In the fall and winter, when days become shorter and colder, other pigments within leaves are unmasked. This is what brings out the orange and yellow colors in leaves that we associate with the changing seasons.

Other factors that can impact fall leaves include wind and rain. If a tree is not exposed to great amounts of wind and rain, the leaves will stay on the tree longer. This will cause the leaves to become more vibrant. However, if it is a particularly rainy season, the leaves will not remain on the trees very long and their colors will not be as bright.

We’d love to see photos of your fall leaves!


Learn more about the processes mentioned in this post here.