A sure sign of fall, the vibrant red oaks show their color down in the valley of nine mile creek, Bloomington, MN (just south of Minneapolis, home of the Mall of America).
Did you know that leaves only turn yellow in Europe? I found this out at Riga Daily Photo (see his yellow-leaf photo). A recent discovery has lead scientists to speculate that the red coloring is a defense mechanism. When the green chlorophyll in leaves disappears in fall, the yellow color that was always there becomes visible. The trees that turn red actually go out of their way to do so. It seems that they do it to ward off insects. In Europe, the combination of Ice ages and the barrier of the Alps managed to kill off all the insects that would threaten the trees, so they don’t need to make the effort. For the full explanation, read this article I found At Science Daily: Why More Autumn Leaves Are Red In America And Yellow In Europe: New Theory