SIOUX CITY | Colors of fall generally reach their zenith this time of year in Siouxland, around the first couple of weeks of October.
That is, if Mother Nature, is on schedule.
"The timing varies," said Jody Moats, park manager at Adams Homestead & Nature Preserve across the river in southeast South Dakota. "The best is when the days are mild and nights are cool, but not freezing."
Moats looked out her window in mid-September and said she could see the colors were already changing.
"It is temperate and weather dependent," added Dawn Snyder, education program director for the Woodbury County Conservation organization. "We're not behind this year. When you see early color, it might be because of stress on the plants.
"A rule of thumb says that the first couple of weeks in October is the peak for color in our region," Snyder said.
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The Loess Hills Scenic Byway remains a popular destination for visitors and residents who aim to get some sort of sensory overload with the bright reds, oranges and yellows autumn can offer.
Those vistas can stretch from the upper reaches of Northwest Iowa (Westfield north to Hawarden and beyond) to the far southern tip of the Loess Hills at tiny Hamburg, Iowa, due east of Nebraska City, Nebraska, "Home of Arbor Day."
"Along major river corridors you'll see good color as that's where trees are more prominent," Snyder said.
Naturalist Charlene Elyea of the O'Brien County Conservation Board asked travelers to refrain from discounting the fall beauty the prairie can offer. While the oaks blaze shorelines throughout the Little Sioux River Valley, one need not look far to noticed the amber-colored prairie grass, as well as hues of purple and yellow.
The Iowa Department of Tourism monitors the timing of fall colors, as does the Iowa Department of Natural Resources. Both agencies share the hottest spots for autumn views on their respective websites.
What, exactly, does cause a leaf to turn color? Basically, the leaf's impending death, that's what.
The green of cholorphyll, through the growing season, dominates the leaf, allowing green to override other pigments. By fall, deciduous plants prepare for a dormant period of winter. Those plants protect themselves by sealing off prior to winter. In doing so, the plant restricts nutrients and water from reaching the leaves. The leaves, which start to die, allow other pigments to show.
"Because (a leaf) doesn't actively have plant water and nutrients coming in, the other colors become more visible," Snyder said.
In species native to Siouxland -- think cottonwoods, silver maples, green ash, basswood and walnut trees -- the dominant fall color might be yellow.
"You go east from here and you'll have more black and sugar maple," Snyder said. "Those are hard trees and they have lots of oranges and red. We don't have them growing wild, but people will plant them and they'll do fabulously well."
Snyder cautioned leaf lovers to do some investigating before they pick up an orange or red leaf for a collection. That leaf might actually be from a poison ivy plant.
"It's tempting for kids to pick up poison ivy leaves," she said. "It's a big leaf that's red and orange. Even though it is dying, it could cause a reaction because it still has the oil in it."
