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Fall colors finally emblazon Iowa

Odd weather across the nation altered peak times

Leaves along the Mississippi River in Marquette show off their fall colors. (Rebecca F. Miller/The Gazette)
Leaves along the Mississippi River in Marquette show off their fall colors. (Rebecca F. Miller/The Gazette)
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This started out as a complicated season for leaf peepers.

As the East Coast sweated through record October heat, parts of the Rockies were buried under wildly early snow. In the Midwest, plains were flooded as levees burst and man-made barriers collapsed. Late heat and early cold can stifle some of the most photo-worthy foliage, but soon enough, large swaths of the country will be engulfed in the brilliant yellows, oranges and reds that herald winter.

And that time in Iowa has finally arrived.

“Most of Iowa is at its peak viewing stage right now and will be for the next week or so,” the Iowa Department of Natural Resources reported Monday in its weekly fall color guide. “Be sure to get out this week to take in the beauty of Iowa’s fall landscape.”

Fall color typically peaks in Northern Iowa around Oct. 10 — with peak colors coming later farther south — but bad weather conditions delayed that a bit this year.

That peak now has been hit in Northeast Iowa and is very close — maybe by this weekend — in other parts of the state, according to the Iowa DNR.

“With the oaks just getting underway and some yellow lingering from the earlier trees, prime fall colors are happening right now and will persist over the next five-10 days,” the agency said about Central Iowa.

Forested areas in the United States host a variety of tree species. The evergreens shed leaves gradually, as promised in their name. The leaves of deciduous varieties change from green to yellow, orange or red before letting go entirely.

During the summer, trees produce chlorophyll, the pigment that turns leaves green and allows trees to harvest light to make food sugars. At the same time, trees manufacture carotenoid, a yellow to orange pigment that is masked by the green chlorophyll during the summer.

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When the production of chlorophyll slows with the onset of fall, the carotenoid’s bright color can emerge. This yellow pigment also helps the leaf absorb different wavelengths of light that the chlorophyll cannot.

Certain species begin to produce another pigment, anthocyanin, when the seasons begin to change. That is what turns forests red and orange. Anthocyanin is also responsible for the red, purple, black and blue colors in certain foods high in antioxidants — think raspberries, purple cauliflower and black rice.

This crimson pigment allows trees to continue storing a little more sugar and nitrogen to have on hand for the next year, according to Paul Schaberg, a research plant physiologist with the U.S. Forest Service.

Some areas of the country are more likely to experience those bright red and orange leaves than others.

New England is a perennial fall destination because of its abundance of tree species contributing bright colors.

But dazzling colors can be seen in plenty of regions outside New England. Wisconsin, Michigan, Minnesota and Iowa along the Mississippi River are great places to go.

Farther south, a mix of oak and hickory forests in Arkansas provides stunning views, especially at higher elevations where there is less development.

Even as far south as New Mexico, yellow oaks can be seen on mountainsides, along with sporadic flashes of red maples.

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Western U.S. forests are predominantly evergreen, where species of juniper, spruce and fir are better adapted to the more extreme temperature and moisture shifts. The deciduous trees in the West, including aspens, tend to display strong yellows.

Across Alaska, yellows and some reds begin to appear as summer comes to an end, lighting up mountain sides with bright colors.

When it comes to tracking down those optimal fall colors, some years can be good, and some years can be bad.

Moderate stress, such as changing seasonal temperatures and the amount of daylight, helps induce the onset of leaf-color change, but more severe stress can mute the vibrancy of autumn’s palette. Drought causes leaves to close up their pores to retain water, limiting their ability to produce sugars and leading the tree to jettison the leaves. Too much water can promote fungal pathogens that can infect leaves, which can also lead to early leaf drop.

But besides the science behind it, the most important thing about fall color, according to the Iowa DNR, “is having the time to enjoy it.”

The Washington Post contributed.

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