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 chlorop