Some scientific types want to understand it while the more existential and hedonistic among us just enjoy it. No questions asked.
It's nature's Kodacrome kaleidoscope—the fall changing of foliage epitomized in places like the Rocky Mountain West, New England and Patagonia.
"I figure it's nature's way of saying she loves us," said Jen Smith.
She's a woman who knows her trees. Smith is a supervisor with the Ketchum Parks and Recreation Department, as well as the city arborist.
"It (the color change) happens at different times every year, and the length of it lasting depends on the year," she said.
Many details of the fall foliage color change are still a mystery to scientists. Environmental factors like moisture, day and nighttime temperatures and even the recent Castle Rock Fire can all play a part, Smith said.
The U.S Department of Agriculture, the umbrella agency for the U.S. Forest Service, has a Web site with an informative section titled, "Why Leaves Change Color."
Color change and the timing of when leaves fall from their branches are primarily dependent on the date on the calendar.
"None of the other environmental influences—temperature, rainfall, food supply, and so on—are as unvarying as the steadily increasing length of night during autumn," the site says. "As days grow shorter, and nights grow longer and cooler, biochemical processes in the leaf begin to paint the landscape with Nature's autumn palette."
Smith said she has heard the autumn display could come earlier this year, perhaps due to last year's relatively dry winter. Aspens are already donning their golden garb in the Wood River Valley and the surrounding mountains and valleys.
But will this year be a peak color year for foliage?
"I think every year's a good year," Smith said. "This year's looking good."
If you see a greater color spectrum in Ketchum's trees there will be good reason for it.
"We are trying to diversify Ketchum and add more color," she said.
Smith and her cohorts have been planting different tree species around town including the areas along the completed and future sections of the Fourth Street Heritage Corridor. Blaze maples will be planted along that thoroughfare.
"Hopefully we will have a variety of color palettes in the fall," she said.
In addition to the many aspens in Ketchum, two or three types of green ash have been planted, and they are changing to yellow right now. There are Manchurian ash, also brilliant yellow, in front of Wrapcity and Desperado's restaurants. Autumn blaze maples can be seen near the Ore Wagon Museum, where they explode in orange-red. There are also birches, willows, other types of maples as well as tamarack, also known as larch, which lend their bright yellows to several Ketchum yards.
In Hailey, where it's 600 feet lower than Ketchum, the leaves have started to change.
"Some have changed in a few places. It's just started," said City Engineer Tom Hellen.
When certain climate conditions are in synch they can produce a "perfect storm" of spectacular color.
"A succession of warm, sunny days and cool, crisp but not freezing nights seems to bring about the most spectacular color displays," says the Forest Service Web site.
Those kinds of days produce lots of sugars and light, and that accelerates the production of anthocyanin pigments that burst with crimsons, purples and reds. The golden and yellow part of the show is fairly constant over the years because cartenoids are always present in the leaves.
Seeing the changing colors here is easy and impressive where there are large stands of trees. Smith suggested Eagle Creek and the 756,000-acre Sawtooth National Recreation Area to the north, and Colorado Gulch and East Fork to the south.
The SNRA should provide some brilliant foliage, perhaps because of recent moisture and cold nights, said Ed Cannady, the SNRA's backcountry recreation manager.
"My guess is that it's going to be a very good year," he said. "I haven't figured out what really turns them on ... and boy they are starting to come on."
Cannady said taking the boat two or three miles beyond the inlet at Red Fish Lake is great for non-aspen foliage. Low-growing scrubs and alders burst with brilliant reds, he said.
If you are going farther afield you may wish to call the Forest Service's Fall Color Hotline at (800) 354-4595. For more background you can go to the agency's Web site at: http://www.na.fs.fed.us/spfo/pubs/fs/colors/colors.htm.
Why trees change color in the fall
Autumn color needs pigment, and Mother Nature provides three: chlorophyll, carotenoids and anthocyanins. According to a U.S. Forest Service Web site here's what those substances do and how they react to weather and climate conditions to make a colorful fall.
Chlorophyll gives leaves their green color, and chemical reactions allow leaves to turn sunlight into sugar for food.
Carotenoids are the yellows, oranges and browns of the color palette exemplified in bananas, corn, carrots and so on.
Anthocyanins produce the reddish-bluish hues of concord grapes, blueberries, plums and cherries.
Chlorophyll and cartenoids are found in what's called chloroplasts of leaf cells during the growing season. A chloroplast is a specialized part of a leaf cell that converts light into plant food. Responding to bright light and excess plant sugar, the majority of anthocyanins are produced in the fall.
As the nights get longer in autumn the chlorophyll production slows down and stops, and all the chlorophyll is destroyed. Then as if at a masked Mardi Gras Ball waiting for their grand entry the carotenoids and anthocyanins take their cue from their friend, chlorophyll, and unmask, revealing brilliant yellows and reds.
The Rocky Mountains in Idaho can be one of the prime spots for fall foliage viewing, but you don?t need to leave the Wood River Valley. This photo was taken near the Sawtooth National Recreation Area, north of Ketchum, and shows a golden stand of aspens. Aspen trees have the widest distribution of North American tree species.
Photo by David N. Seelig
