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Autumn begins: Will weather pattern leave leaf-peepers blue?

On first day of autumn, thoughts often turn to the coming blaze of fall foliage. But in New England, an unusually hot and dry summer may portend a shorter, and paler display this year.

By Sara AfzalContributor / September 22, 2010

Tree branches laden with the multicolored leaves of fall are seen in Portland, Ore., Wednesday. Today is the fall equinox and first day of autumn.

Don Ryan/AP

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Boston

Autumn has arrived, and with it visions of leaf-peeper caravans snaking their way by brilliantly colored, sun-lit trees along tranquil rural roads, of crisp nights spent at cozy country inns and B&Bs.

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That is certainly the image promoted by state departments of tourism, inn keepers’ associations, and countless travel websites, which eagerly anticipate every fall’s rush of business.

But fall foliage seasons, and the leaf chemistry that creates them, are notoriously vulnerable to weather conditions, and this year may be a case in point after a summer of extreme heat and dryness in the Northeastern US, where some of the more vibrant displays of color can usually be found.

“This year we had an exceptionally dry and warm August and early September,” said Richard Primack, a professor of biology at Boston University in Massachusetts, “so this caused a lot of birch trees and other trees to lose their leaves prematurely.”

The best autumn foliage follows growing seasons with ample water followed by cool and dry weather in early fall. With dropping temperatures and less daylight, the leaves lose the chlorophyll that makes them green, leaving underlying pigments of red, yellow, and orange.

The diversity of tree species in New England make it the region best known for peak foliage, explains Andrew Richardson, an assistant professor of biology at Harvard University in Cambridge, Mass.

“The reason the colors are so strong in New England is that many native species [red and sugar maple, red oak, dogwood, cherry, and ash] produce anthocyanins,” he said. Anthocyanins are pigments found in plants that are believed to protect plant tissues from some wavelengths of light, such as ultraviolet. “Species which do not produce anthocyanins – birch, beech, and poplar, for example – don't have such colorful foliage.”

New England industry

In the northern New England states of Maine, New Hampshire, and Vermont, foliage season occupies an important place on the tourism industry calendar. On the website of Vermont’s Department of Tourism and Marketing, a map shows that Vermont’s foliage will peak throughout mid-October.

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