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Local Fall Colors Reaching Their Peak

By Todd Von Ehwegen, Natural Resource Manager – Environmental Education, Cerro Gordo County Conservation Board –

The transformation of leaves into a beautiful array of colors is an annual phenomenon anticipated by many, but few understand what actually causes the change.

As the length of daylight decreases, trees produce a chemical called phytochrome, which triggers them to begin gearing up for dormancy. The production of chlorophyll, a compound in the leaf that manufactures food for the tree, begins to slow and eventually ceases.

Chlorophyll gives leaves their green color. As the production of this compound decreases, other colors begin to show up in the leaves. These colors are always present, but the green chlorophyll covers them throughout the growing season.

Another factor that causes color change is a sugar build up in the sap as water flow in the tree decreases. Pigments then form in the sap that cause the leaves to turn red or purple depending on the acidity level. There can be many variations of colors in trees due to variations in pigments and acidity.

Some generalizations of colors you can expect to see, how the colors are formed, and what trees have them are as follows:

1. Yellows/oranges (pigments appear as chorophyll production decreases): soft maples, elms, ashes, hickories, aspens.

2. Reds/purples (sugar build up in sap, forming pigments): hard maples, oaks, sumacs, dogwoods, Virginia creeper.

3. Brown (pigments appear as chlorophyll production decreases): bur oaks.

Bright sunny days followed by cool nights produce the best fall color viewing. Dryer weather enhances red pigment formation because there is a greater buildup of sugars in the leaves. Cloudy days and warmer nights cause the chlorophyll to break down more slowly, and pigments are not formed as quickly, diminishing fall color.

Contrary to popular opinion, frost does NOT enhance fall colors, but instead causes premature dropping of leaves. Below-freezing temperatures also inhibit the production of red pigments. Lots of wind and rain are also undesirable because they cause the premature dropping of leaves.

On most trees in autumn, an abscission layer is formed where the leaf stalk connects to the branch, eventually causing the leaf to drop off and initiating the annual fall chore of raking leaves.

The Fall Color Report on the Iowa Department of Natural Resources website predicts peak fall color weekends in North Central Iowa to be October 6 & 13. A leisurely drive around Cerro Gordo County past several conservation board areas can provide excellent local viewing.

Start at the Lime Creek Nature Center just north of Mason City. Take a short hike along one of the woodland trails, or on a prairie loop to enjoy the prairie and views of the colorful woodland edge.

From Lime Creek follow blacktop B-20 to Rock Falls. Take S-62 north out of Rock Falls one mile to White Wildlife Area. This wooded area along the Shellrock River is a colorful spectacle in the fall. It has a boardwalk that traverses a wetland area to the woodland trail.

From White Wildlife Area go back south to Wilkinson Park in Rock Falls. A drive south through the park will provide beautiful views of the river, colorful trees and shrubs, and a native prairie in its fall splendor.

Continue travelling south along the Shellrock River into the Shellrock River Greenbelt and Preserve. This four-mile stretch along the Shellrock River leads through woods, meadows, and ponds for a variety of colorful landscapes.

The Greenbelt road will exit onto Highway 122 just west of Nora Springs. Take 122 east to blacktop S-70 and proceed south 5 miles, then take 225th Street west three miles to Claybanks Forest. This 56-acre forest contains a locally rare stand of hard maple/basswood timber, which provides a stunning autumn show.

From Claybanks go east one-half mile to Wren Avenue and turn north, cross the Winnebago River, then go west on 230th Street for a scenic four-mile drive along the river to blacktop S-56 and Portland. From there take S-56 north back to Highway 122 and Mason City.

As a part of our “Recreational Experiences Close to Home!” promotion, the Cerro Gordo County Conservation Board has developed a flier on fall colors and where to view them. This flier can be downloaded from our website: (click on outdoors), or call 641-423-5309 to request one.

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