This year around Colorado we have a remarkable number of bright red Aspen leaves. This is unusual, as most of our Aspen tend to be the standard “gold” types.
The timing of leaf coloring til leaf fall is dependent on the increasing length of night. As the days grow shorter, a tree’s biochemical process shifts and its production of chlorophyll slows and eventually ceases. As the leaf’s chlorophyll is used up by the tree, other color pigments—carotenoids and anthocyanins—become visible. According to the Forest Service “Both chlorophyll and carotenoids are present in the chloroplasts of leaf cells throughout the growing season. Most anthocyanins are produced in the Autumn, in response to bright light and excess plant sugars within leaf cells.”
It is almost as though the trees are celebrating this gorgeous end of summer, trying to postpone the inevitable long and cold winter days ahead.