Sometime between now and the middle of November, the trees in North America's eastern broadleaf forests will reach their full fall glory. From Vermont's Northeast Kingdom and New Hampshire's White Mountains to the Shenandoah Valley and beyond, leaf peepers will bring traffic to a standstill on beautiful fall weekends. By the carful and busload, they'll come to gawk at the beautiful countryside. But what will they be seeing?
To begin with, leaf color arises from various chemicals within trees. It's the strength as well as the presence or absence of compounds like tannins, xanthophylls, and carotenes that determines fall hues in the scores of tree species found in the East.
Back in the spring and summer, when the millions of trees in these same woodlands were busily growing and producing food, their leaves were chock full of chlorophyll, and it was the chlorophyll that colored the forests varying shades of green. But chlorophyll is a mask, and once trees sense the change in the weather and start to stop chlorophyll production, the mask drops and the other colors of the leaves come to the forefront.
The fall colors can be so distinctive in some tree species that it's possible to identify these trees from a distance merely by noting their hues. The brilliant red leaves belong to the Red Maple, American Mountain Ash, and Black Tupelo, plus sumacs, blueberries, and Virginia Creeper in the understory. Richer red foliage is typical of Red Oak, Scarlet Oak, and White Oak. Birches and beeches sparkle with bright yellow foliage, while Witch Hazel and Striped Maple are a less intense yellow, and walnuts, hickories and aspens attain a truly golden glow.
Of course, not all trees settle on a single color. Sugar Maples, for example, blaze in green, yellow, orange, and startling red, and Sassafras comes in various shades of red, orange, yellow, and purple.
If you want to enjoy the fall colors yourself, plan ahead and, if possible, venture out during the week as opposed to on a crowded weekend. No matter when you go, though, spend a little time outside your car. The trees are even prettier close-up, along a quiet trail or down a less traveled side road.