Technicolor Time in New England as Neon-Bright Leaves Fall : Autumn : The foliage shows of the ‘fifth season’ are rarely matched elsewhere, thanks to variables of temperature, rainfall and Mother Nature’s magic.

To everything there is a season, Ecclesiastes tells us. On Earth, we have four -- mostly. In a very few places, especially New England in the United States, there is a brief but spectacular fifth season. It is leaf season--a short, late-September/early October interlude that transmogrifies hardwood trees into an amazing technicolor dreamscape.

The late Vermont columnist Louise Andrews Kent, through a fictional protagonist, had this to say about the beginnings of that change: “Her favorite foliage season is not the full burst of blazing color. She likes best the time when beech and birch leaves are still green among the reds and yellows of the maples, when there is still green on the maples themselves and when elms are great arches of gold.”

Botanists and other tree folk generally agree that, although fine autumn displays may be found as far afield as Japan, the fall foliage shows of a few blessed American states are rarely matched, never exceeded. This is due mainly to the phenomenal, neonlike reds of the sugar maple. These glowing colors have brought fame, and a degree of fortune, particularly to Vermont and New Hampshire.

Sugar maples that produce these beautiful colors are not limited to the New England states. South-Central Pennsylvania is also home to sugar maples, as are small “sugarbush” areas in Virginia and West Virginia. In New York state, the Finger Lakes region and the Adirondack Mountains put on gorgeous shows with a variety of colorful maples and other hardwoods.

A growing number of Europeans are among the tourists to these and other Northeastern and Midwestern states. “They have no idea about fall colors,” said Dr. John Wurdack, botanist emeritus at the Smithsonian Institution’s National Museum of Natural History in Washington, D.C. “European maples are pretty drab affairs in the fall. In fact, most European trees are pretty drab.”

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“It’s unnatural,” one autumn visitor to New Hampshire was heard to exclaim at the sight of a hillside display of fall foliage.

“Well,” Wurdack responded, “it has something to do with our climate. That’s about all you can say--that these tree species developed that way.” Other than the basic chemistry, he said, no one knows precisely which variables of temperature, rainfall and other factors are most important in producing the yearly palette of colors.

But they do know that there are threats to this beauty. Last year, for example, tiny insects known as pear thrips began attacking sugar maples in Vermont. Throughout the “sugar-maple belt” of New England--one in every four trees is a sugar maple--pear thrips have caused significant defoliation, said Dr. Bruce Parker, a professor of entomology at the University of Vermont.

More than 2 million trees have been infested, Parker said, an infestation that is expected to have an impact on Vermont’s tourism and sugar-maple industries. Scientists and many other people hope that a fungus, which kills the soil-borne insects, can be introduced to slow or halt the spread of pear thrips.

So far, the pear thrips problem has been limited, Parker said, and plenty of trees remain in New England for the annual tourist crowds. Healthy trees wait until the shorter days and cooler nights of late September and early October to signal their annual color change.

Along with the pear thrips, observers have warned that maples, yellow birch and white pine are starting a slow move northward into Canada. Global warming, the result of a buildup of carbon dioxide and other gases in our atmosphere, may be behind this shift of the trees to cooler latitudes.

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With cooler autumn temperatures, chlorophyll in tree leaves, which is responsible for their green color, starts to break down. Carotins and tannins--yellow and orange pigments in the leaves--are slowly revealed. Chip Tynan, who oversees the Answer Service of the Missouri Botanical Garden in St. Louis, explains that carotins and tannins are found in the leaves all summer, but are usually invisible to the human eye because they’re masked by chlorophyll.

Vivid pink, red and purple pigments, Tynan said, are the result of anthocyanins, a byproduct of sugars. Warm sunny days produce sugar in a tree’s leaves. When autumn nights fall below 45 degrees, the sugars are trapped in the leaves, causing the accumulation of anthocyanins and brilliant foliage.

The audience is never sated. Public enchantment with the leaves of autumn reaches across the country, into areas where ecosystems differ widely from that of the northeast.

Tynan reports that people start calling the Missouri Botanical Garden in June to prepare for their fall vacations, asking whether there will be fall color in the Ozark Mountains.

“We always like to tell folks here, even more so than in New England, that here in Missouri we may have a truly outstanding year maybe only one or two years out of five,” Tynan said. “But we always have some color.”

While Missouri’s leaf seasons don’t have “the neon and the flash” of New England autumns, they’re lovely in their own right, he adds.

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“Better an oak than a sycamore,” he said, referring to the contrast between red oak leaves and the yellow leaves of sycamores. “We take what we can get.”

Fascination with the scenic turning of the seasons is a relatively recent phenomenon. Before World War I, the return-to-nature movement, symbolized by the building of rustic camps throughout New England, focused almost entirely on the joys of summer. Fall tourism came into its own with nearly universal ownership of the automobile. As Vermont, New Hampshire and upstate New York were to discover, there’s more than the autumn gold of aspen and birch in them there hills.

Tiny Vermont is still largely rural and, with a population of fewer than 600,000 people, ranks 48th among the 50 states. But sugar maples account for 34% of all Vermont hardwoods. This purely serendipitous byproduct of a profitable maple-sugar industry swamps the state with 800,000 tourists--known as leaf peepers--each year. They come by car, by tour bus and by plane. They reserve hotel and motel rooms months ahead, and they leave behind a whopping $80 million.

Such bonanzas are not lost on tourist development offices of other states with claims to fall beauty. Kentucky, Montana, Texas and Arkansas, among others, now woo leaf peepers with all the accoutrements of development: publications extolling the beauties of the season; toll-free telephone updates tracking the progress of emerging color and predicting when the display will peak along a given road; suggested motor tours; recommended hiking and biking routes, and advice on accommodations.

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In the Northeast, campaigns are no less assiduous. New York state’s information packet takes prospective visitors to obscure vantage points, like the Shawangunk (pronounced SHON-gum) Mountains, and advises leaf peepers to savor the fall color from canal boats and vintage railroad cars. New Hampshire provides an official guidebook that includes color pictures to help identify leaves, from sumac to large-toothed aspen. The Massachusetts Fall Foliage Guide recommends, under the heading “Unusual Ways to View Fall Foliage,” balloon and glider trips and chairlift rides.

Some leaf seasons are muted, others incandescent. The vividness of a given autumn, scientists admit, is something of an imponderable. The Missouri Botanical Garden’s Tynan comments that “lurking in the back of my mind, I know that I’ve seen exceptions to all the standard, commonly assumed series of events that must occur.

“There are some years when we have had very dry summers, poor growing seasons and yet, very, very good fall colors,” he adds. “Something else kicks in--timely rain and just the right combination of sunny days and cooler nights. I don’t think that anybody really knows the answer. It’s a mix of all these factors.”