As I write this column on a late September morning in the wooded country of Bowdoin, I’m distracted by the view from my kitchen window. Outside, where this hiker would rather be, walking the paths among the trees, I can clearly see the steady progress of autumn.

Across the field, the leaves of the ash and birch trees are turning golden yellow. Edging the swamp, the maples are starting to show their classic crimson red, and the alders are blushing as well. On the hillside, the still bright-green canopy of sugar maples is splashed with oranges and yellows.

Curious about what’s happening with the onset of fall in other parts of the state, I check the Maine Foliage Report at www.mainefoliage.com.

Maintained by the Maine Department of Conservation, the site is a great resource for hikers wanting to plan their treks to coincide with the best of the fall colors.

The foliage map, segmented into seven regions, confirms that the season is in full swing, with high and peak colors from western and central Maine through Aroostook County, and moderate coloration in southern and coastal Maine. The shift will be dramatic over the next few weeks as the waves of color move southward.

“Every year, Maine Forest Service forest rangers collect the data and report back,” said Gale Ross, Maine foliage spokeswoman. “That’s how the fall foliage map is put together.”

Enthusiastic leaf peepers are encouraged to share their experiences by posting comments and photos on the conservation department’s new Facebook page, “Maine Fall Foliage,” Ross noted.

Tracking the progress of the foliage is fun, and getting out into the woods on foot to view the kaleidoscope of bright colors is delightful. But what about the science behind this phenomenon? What actually causes the leaves to change color?

“The process is triggered by the shorter daylight hours and cooler temperatures,” said Peter Lammert, a state forester.

The combination causes a cork-like substance to form at the base of the stem, or petiole, of the leaves of hardwood trees. This abscission layer stops water from moving up the stem to the leaf.

“That’s when the chlorophyll factory shuts down,” Lammert said.

Through the process of photosynthesis the chlorophyll in the leaf converts carbon dioxide, water and light energy into sugar (food for the tree) and oxygen (a component of the air we breathe).

Without water to do its job, the green chlorophyll gets broken down by sunlight, revealing the carotenoid pigments underneath — the yellows, oranges and browns. And as fall progresses, another leaf pigment called anthocyanin is revealed. These are the reds and purples.

Lammert said this year’s low rainfall and dry soils are affecting the foliage. Sugar maples, for example, are turning as much as a month early. And many red maples are displaying an unusual bicoloration of red and green, not only over the entire tree, but often on the same leaf.

Poplars, notes Lammert, are typically the last to turn color (yellow). And those brown leaves that hang on through the winter? Those are white, pin and scarlet oaks, which along with beech, have a different type of abscission layer. They typically won’t drop their leaves until spring.

Hardwoods aren’t the only trees showing their colors now. Look closely at the white pines and you’ll see a golden brown tinge where one of the three sets of needles has died and is about to be shed. And soon the tamaracks, one of the few deciduous conifers, will also turn gold and shed their needles.

When the colors start to peak, Lammert likes to bushwhack into a stand of sugar maples — his favorite tree species — to enjoy the mix of brilliant reds, oranges and yellows.

“I like the sugar maple for its beautiful shape, its strong trunk and limbs,” Lammert said. “And it provides maple syrup and good firewood.”

Hikers have their own favorite fall hikes. I like to mix it up with hikes that remain beneath the forest canopy, where I can feel fully immersed in the rich hues and smells of autumn.

Other times I prefer to hike up high, to the peaks and ridges, to get a good look out over the seas of colorful woods.

But really, no matter where you hike right now, it’s going to be great.

 

Carey Kish of Bowdoin is a freelance writer and avid hiker. Send comments and hike suggestions to: [email protected]