SIOUX CITY | The transformation of leaves on most trees in Siouxland from green to orange, reds and yellow is happening later than normal this fall.
Kevin Pape, a ranger at Stone State Park, said the fall colors in in the Sioux City park are about one to two weeks behind a typical year. In northern Iowa, the change typically begins in is the last week of September or first half of October.
"I think this weekend is going to be prime time," said Jeff Seago, area forester for the Loess Hills Forest in Pisgah, Iowa, amid the distinctive hills that only exist in Iowa and China.
Barb McGee, of Peterson, Iowa, in the Little Sioux River Valley, said trees there only began to turn on Monday.
"The leaves are starting to change and it looks like the ash trees are getting beautiful, are turning real yellow. The rest of the trees are still green in the valley," McGee said.
The seasonal change also has started in a range of plants, including poison ivy, which hikers take pains to avoid.
"(Poison ivy) is probably my favorite fall plant," said Seago.
Seago acknowledged people are always quite surprised to hear poison ivy changes to yellow, orange-mango and deep red.
"Everybody is afraid of it, but it is an absolutely beautiful plant. One vine can have all the colors at one time, and they do right now," he said.
Area byways draw people on motorcycles, cars and bicycles for what are often called fall color tours. The Travel Iowa state agency touts options for people to journey through.
The Loess Hills Scenic Byway, which extends from Plymouth County south to the Missouri border, is a popular route. Additionally, Iowa Highway 12, which runs past the entrance in Stone State Park on the west edge of Sioux City, often has golden leaves on both sides of the road, thereby earning the the Golden Corner nickname.
The annual Artisans Road Trip that goes through the Little Sioux River Valley took place Oct. 14-15. It is a self-guided tour of byways and back roads for people looking for art treasures in that vicinity of Siouxland. The road trip route goes along some of the Glacial Trail Scenic Byway in Buena Vista, Cherokee, O'Brien and Clay counties along the Little Sioux River.
McGee owns McGee Gallery and Framing, which is on the road trip. She said the event is held annually on the second weekend of October, when the fall colors often are in bloom. This year the colors hadn't turned. In other years, a killing frost may have resulted in leaves plummeting off trees by the time of the tour, so the best time can be a moving target.
"It gives them an incentive to go, because the leaves are going to be pretty," McGee said.
The change from green to other colors is spurred by a chemical called phytochrome, which allows chlorophyll production and makes trees go dormant. The loss of chlorophyll allows other colors to push through the green. Leaf pigment is influenced by the amount and acidity of sap in trees; more acidic sap gives more reds and brighter colors.
Seago works in the forest that covers 11,600 acres in Harrison and Monona counties. He said Preparation Canyon State Park near Moorhead, Iowa, is a popular fall spot.
"Preparation Canyon, when I drove through it on Monday, it was beautiful, Seago said. "We have seen an increase in visitors in the last two weeks. I think that is correlated to fall colors."
Seago noted the tree colors change as the days move further into October. One of the later changing trees are silver maples, which will soon become more yellow. Others will become a blah brown.
"The oranges and reds people like to see for contrast, I think we will lose that in the next week," he said.