A Breakdown of How and Why Local Trees Change Colors

Every fall we see the leaves change color, but what’s the science behind the process?

With fall comes pumpkins, scarecrows and fields full of corn, but what makes Wisconsin truly special during the fall season is the color change in the trees.

Every year, the leaves change from their typical green color to various shades of red, orange and yellow bringing beauty that inspires hikes throughout Milwaukee or even a drive up to Door County.

But what is the science behind the change of color?  It’s all so mysterious, and yet, so routine. Here’s the scientific scoop on why our local trees change colors like they do:

Trees By the Color


Why Green?


Throughout the summer and spring seasons, the majority of trees have a green color to them. This is due to Chlorophyll. Chlorophyll is essentially a pigment that takes in sunlight and turns it into the tree’s food sources.

The warm temperatures and sunlight of Spring and Summer are used to produce chlorophyll, so when the fall and winter months come along, not as much chlorophyll is being produced. This results in the absence of the green color.

“So when we get to fall, the fall season, short days mean the sunlight is less intense,” said Colleen Matula, an ecologist for the Department of National Resources. “Chlorophyll produces that green color in the leaves but when we get to fall, we have less Chlorophyll in the leaves … when there’s less chlorophyll, the green fades away and the other pigments are revealed such as the reds, yellows and so forth.”

Why Red?


Some trees turn a red color at the beginning of fall and this is due to the breakdown of the chlorophyll. When the chlorophyll is leaving the leaf, we are able to see a different pigment called anthocyanin causing the red color. The shade of red may vary depending on the tree, some even having a purple or brownish-red tint to it, according to Matula.

Some trees that are notorious for their red color include the red maple, scarlet oak and the staghorn sumac.

Why Orange?


Did you know that if you eat too many carrots that your skin can turn an orange-ish color? Carotenoids are part of the colorization reasoning behind carrots and pumpkins. Knowing that, it should be no surprise that one of the reasons why leaves turn orange is due to the carotenoid pigments, too.

Carotenoids tend to leave the leaf at the same time as the chlorophyll; however, the rate in which it leaves the leaf is much slower. This allows the orange color to be shown after the green leaves the leaf.

“Trees such as aspen and birch, have the carotenoids colorization in their leaves,” said Matula.

Why Yellow?


So like the other colors, it only makes sense that there is another pigment that will make the leaves turn yellow. According to Matula, that pigment is called Xanthophyll with a combination of Carotenoids.

 Where and When to See Fall Colors

YOU SHOULD be able to see the colorful leaves soon. According to Travel Wisconsin, Milwaukee County will be at peak color-changing season during the third week of October, which gives you plenty of time to find all of best spots to take in the fall scenery

One of which is Harrington Beach State Park in Belgium. Harrington is approximately 45 minutes north of Milwaukee by car, but is worth every minute of the drive. There are plenty of ruins from a former mining community, including buildings and a railroad – which you can see remains of in the quarry.

If you’re not looking to travel so far, Lake Park in Milwaukee is always an option too. There’s lots of space and trees to see the changing leaves while not having to commit to a commute. Not to mention, Lake Park is close to the water, meaning the leaves will start to change sooner.

“Trees along wetlands tend to produce colors first because they are getting a little stress from all the moisture they have been getting,” said Matula.

For a comprehensive list of places to check out leaves this summer, check out Milwaukee Magazine‘s top picks.



Corey Schmidt was an editorial intern for Milwaukee Magazine in Fall 2020. Currently, Corey is a junior at DePaul University where he majors in both French horn performance and communication & media.