The Buzz

Five fun facts about the season's much-anticipated color show

The fall color display at Goodenow Grove Nature Preserve
Goodenow Grove Nature Preserve. (Photo courtesy of Lorenzo Pesce)

There's plenty to love about fall — the chill in the air after months of heat and humidity; visits to apple orchards and pumpkin patches and corn mazes; and pumpkin spice everything. But perhaps the most anticipated event each fall is the changing of the leaves, a final dazzling display courtesy of Mother Nature before our too-often drab and dreary winter settles in.

Taking time to enjoy the yellow, orange and red hues that color the fall landscape is so popular it's even generated its own term — leaf peeping. Here in Will County, the peak season for fall color is typically in mid-October.

Before you plan a leaf-peeping adventure of your own, check out these five facts you might not know about the annual fall color display.

Those fall colors are always there; you just don't always see them

The pigments that create the vivid yellows and oranges that paint the fall landscape have been present since the trees leafed out in spring; they've just been masked by chlorophyll, the pigment that gives leaves their familiar green color. The colors in the leaves — whether the cool green shades of summer or the warm hues of fall — are all the result of pigments, and different pigments produce different colors, according to the National Oceanic and Atmospheric Administration.

Chlorophyll is responsible for the green color in leaves, while xanthophylls create yellows, carotenoids make oranges and anthocyanins make reds, the NOAA reports. In spring and summer, leaves produce a lot of chlorophyll because it is necessary for photosynthesis. The other pigments are also present, but not in the same quantities as chlorophyll, so the other colors are not expressed in the leaves.

When the amount of daylight each day begins to get shorter as summer turns to fall, it signals the leaves to stop making chlorophyll. When this happens, the green color fades away, and those other pigments are expressed in the familiar yellows, oranges and reds we love to see each fall. The particular color of a particular leaf results from how the different amounts of the yellow, orange and red pigments combine with one another, according to American Forests.

Weather is key

Pigments are responsible for the changing color of the leaves, but how bright and vivid the display is each year has a lot to do with the weather. Temperature and moisture are the two main weather factors that affect the annual fall color show, according to the U.S. Forest Service

If a dazzling display is what you hope for each year, keep your fingers crossed for periods of warm, sunny days and cool — but not freezing — nights. During warm, sunny days, leaves produce a lot of sugars, but the cool nights prevent the sugars from leaving the leaves, the forest service reports. This will create a more dazzling color show. 

Even the weather many months before autumn can affect the fall display. A late start to spring or a long period of summer drought can push back the peak period of fall color by a few weeks, and warm weather in early fall can make the display less vivid than usual, according to the forest service. And rainy and windy days during the peak color period can shorten the display because the leaves will quickly be swept off the trees.

Different trees produce different colors

Fall color varies from year to year, but mostly only in the vividness and intensity, which is due to the weather. The actual color of the leaves — whether yellow or red or even purple — is determined by the pigments, and certain trees have leaves that turn certain colors. 

Our local trees that produce deep red and orange and bronze-colored leaves include red oaks, sugar maples, flowering dogwoods, persimmons, sweet gums, sumacs and tupelo gums, according to the Illinois Department of Natural Resources. Bright yellow and orange leaves are seen in ash, birch, black cherry, cottonwood, hickory, sassafras and tulip trees. The deep purples and reds are typically seen on vines like poison ivy and Virginia creeper.

After the fall color starts to fade away, we're left with a lot of brown leaves. This late autumn color is the result of chemical substances called tannins that are present in all leaves, as well as other plant matter, including bark, buds, fruits, roots, seeds and stems, according to the forest service. The tannins are found in cell membranes, and in combination with the pigments in the leaves, they can influence the fall colors. However, after all the pigments break down at the end of the season, only the tannins remain, which is why the final color for the leaves is brown.

The color change is part of trees' winter prep

The changing color of leaves in fall is part of how deciduous trees — the trees that lose their leaves each year — prepare for winter. After the leaves change to their familiar fall hues, the next step is for them to drop. This shedding of leaves allows the trees to conserve water and energy during winter, when conditions are harsh, EarthSky reports. 

In late fall, when winter is imminent, changes in hormone levels in the tree begin the process of abscission. Through abscission, the tree will block off its connection to the individual leaves by creating a layer at the leaf base called the abscission layer. This stops the flow of nutrients and chemicals back and forth between the leaves and the tree. Eventually, the leaves will fall from the tree.

Losing their leaves in autumn is unique to the temperate forests in North America. In tropical forests, deciduous trees do shed their leaves, but they do it at the start of the dry season, EarthSky reports. Tropical trees shed their leaves for the same reason as the ones close to home: Conditions during the dry season are harsh, and the leaves can be damaged or destroyed.

Leaf peeping is big business

Will County produces its share of show-stopping fall color, but it's certainly not the leaf-peeping destination that New England is, or, a little closer to home, Door County, Wisconsin, or even the Starved Rock area are. For these places, leaf-peeping is big business — to the tune of millions and even billions of dollars a year.

New England is perhaps the biggest fall foliage hot spot, with many states in the region issuing fall color forecasts in an attempt to draw tourists in for leaf-peeping adventures. And with those tourists come dollars spent on hotel stays, restaurant visits, recreation and more. 

Exact figures are hard to come by, but it's safe to say leaf peeping is big business for communities in New England, the upper Midwest and beyond. In 2013, the forest service estimated fall foliage tourism brought in $8 billion in revenue for New England. And Vermont alone brings in about $460 million annually thanks to fall foliage tourists, according to the National Environmental Education Foundation.

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