Every fall deciduous trees put on a wonderful show of color before dropping their leaves in preparation for the winter months. Although the trees of the Inland Northwest aren’t quite as famous for this display as their cousins of the Midwest and East Coast, the colors that blanket the land each autumn are still impressive.
As most people know, deciduous trees are those that drop their leaves annually. Although primarily hardwoods, there is one local conifer, the western larch, that partakes in this ritual. Larch trees have been known to meet an early demise when landowners not familiar the species notice that “the beautiful evergreen tree in the yard seems to be dying!”
Why do some leaves change color in the fall? It is often assumed that colder temperatures are the cause; whereas in reality, a phenomenon called photoperiodism, or the relative amounts of day and night, regulates this and a number of other biological processes in a tree. As days become shorter, the amount of chlorophyll, the substance that gives leaves their green color, is reduced. In addition, there is a broad spectrum of other colors present in all leaves, but green is reflected so strongly by the chlorophyll that it is the color most visible to the human eye. As the amount of chlorophyll lessens, other colors become apparent, producing the wonderful colors that we enjoy each fall.