Grit – September 01, 2019

(^32) September/October 2019

Fall

Foliage

Each

year, the lush green of summer turns into the drabness of winter as

trees lose their leaves. But the transition in fall typically offers a spec-

tacular panorama of color. For some New England states, it’s a major economic

factor. “Leaf peeping,” where tourists gather to see the fall colors, is a multibillion

dollar industry. The shift from summer green to warm autumn hues is purely bio-

logical, so the beauty is serendipitous.

Although there’s variation from one autumn to the next, an overall pattern

repeats itself every year because the display is part of a tree’s annual life cycle.

Deciduous trees, primarily the hardwoods, are only active during the warm,

freeze-free growing season. Leaf buds will expand in spring, and new leaves will

emerge as the air warms. The “job” of the leaves is to gather the abundant sunlight

of summer and use this energy to produce food: sugar. The leaves have a large sur-

face area, better for collecting more light, and are typically thin to reduce weight.

But these leaves can’t withstand the freezing temperatures of winter. Internal water

would freeze, rupturing the vascular transport system. With the shorter days and

cooler temperatures of fall, these trees “know” it’s time to shed their leaves and

shut down for winter.

Learn how the life

cycles of deciduous

trees contain the key

to the brilliant

autumn colors that

grace us annually.

By Dr. Ed Brotak