Who doesn’t love fall? There’s pumpkin patches and corn mazes and, of course, trick-or-treating on Halloween. One more thing people look forward to each year is the changing of the leaves and the colorful display we can enjoy before our dreary winter settles in.
Taking time to enjoy the yellow, orange and red hues that color the fall landscape is so popular it even has its own term: leaf peeping. Here in Will County, the peak season for fall color is typically in mid- to late October.
Before you plan a leaf-peeping adventure of your own, here are five facts you might not know about the annual fall color display.
Those fall colors have always been there
The pigments that create the yellows, oranges and reds that paint the fall landscape have been present since the trees got their leaves in the spring. Until fall, the colors are masked by chlorophyll, the pigment that gives leaves their familiar green color. The colors in the leaves are all the result of pigments, and different pigments produce different colors.
Chlorophyll is responsible for the green color in leaves, and xanthophylls create yellows, carotenoids make oranges and anthocyanins make reds. 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.
When the amount of daylight each day begins to get shorter as summer turns to fall, the leaves 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.
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.
Words to know
Abscission: The process by which leaves and fruit detach from a plant.
Anthocyanin: A blue, violet or red plant pigment.
Carotenoid: A yellow, orange or red plant pigment.
Chlorophyll: A green pigment used by plants for photosynthesis.
Deciduous: Shedding its leaves annually.
Photosynthesis: The process by which green plants and some other organisms use sunlight to synthesize foods from carbon dioxide and water.
Tannin: An organic substance found in plant tissue.
Xanthophyll: A yellow plant pigment.
For a more dazzling display, we need periods of warm, sunny days and cool nights. During warm, sunny days, leaves produce a lot of sugars, but the cool nights prevent the sugars from leaving the leaves. 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. Warm weather in early fall can make the display less vivid than usual. And rainy and windy days during the peak color period can shorten the display because the leaves will quickly fall from 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 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. 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 other plant matter. 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 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.
In late fall, 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.
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. There, leaf-peeping is big business, generating millions or 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.
Exact figures are hard to come by but, according to the forest service, fall foliage tourism brought in an estimated $8 billion in revenue for New England. And Vermont alone brings in about $460 million annually thanks to fall foliage tourists.
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