Why do leaves change color in the fall?

Updated: Oct. 11, 2022 at 12:00 PM CDT
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QUAD CITIES, Iowa/Ill. (KWQC) - As we get deeper into the month of October, the leaves on the trees will continue losing their green color, leading to different shades of yellows, oranges and reds throughout the fall season.

But why does this happen?

During the growing season, trees produce chlorophyll which gives the leaves its green pigment.

The pigment absorbs light which is then turned into energy that feeds the trees, a process known as photosynthesis.

During the autumn months when there are big changes to the length of daylight combined with the cooler temperatures, the chlorophyll breaks down, leading to the change in colors of the leaves.

Yellow leaves are due to zanthophyll.

Orange leaves are the result of carotene, the orange or red pigments also found in carrots and other plants.

The reds on leaves are from anthocyanins, which are also responsible for the colors blue and purple other plants.

The brightness of the colors in autumn depend greatly on the weather.

A warm and wet spring, combined with drier weather in the later parts of summer tend to lead to more vibrant colors during the fall, with sunny autumn days and cool night, but not cold enough for frost, which can lead to less vibrant colors.

The amount of moisture in the soil can affect the colors of fall.

A late spring or a severe summer drought can delay the onset of peak fall colors by a few weeks.

After the leaves change the stems develop a layer of cells that breaks down the tissues that supports the leaves, leading to the leaves fall off the tree.

As you plan your leaf peeping trips this season, the last week of September through the second week of October is usually when fall colors peak in northern Iowa.

For most of the TV6 viewing area north of Interstate 80, the first through first weeks of October generally see the most vibrant colors.

In southern portions of the viewing area, the second through fourth weeks in October produce the greatest fall colors.

Click here for the latest Iowa Fall Color Report.

Click here for the latest Illinois Fall Color Report.