Why leaves change color in the fall

Everyone admires the splendor of fall color but very few know why trees turn brilliant shades of red, orange, yellow and purple. We thought you’d appreciate knowing more about the process that’s responsible for the stunning show, in a summarized explanation for the non-scientist.

If you recall back to biology class, photosynthesis is the process that allows plants to turn water and carbon dioxide into oxygen and glucose – the latter which is used as food for energy and as building blocks for growing.  This food-making process takes place in the leaf in numerous cells containing chlorophyll, which is also the chemical responsible for giving leaves their green color.

While this process hums along during the spring and summer, autumn brings about shorter days which serves as a heads up to trees that it’s time to get ready for winter and they respond by shutting down their food-making systems. This is when the green chlorophyll starts to break down and the green color disappears from leaves.

Once the green starts to fade away, we start to see yellow to orange colors which have always been present but covered up by the green chlorophyll.  At the same time other chemical changes may occur, which form additional colors through the development or red anthocyanin pigments.  Some mixtures give rise to reddish and purplish fall colors while others give us stunning oranges. It is important to note that this process only happens in deciduous broad leaf trees, not evergreens.

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