Aspen Trees

aspens changing color at the base of the Absaroka Range

The stunning yellow leaves of aspen rustling in the wind add a soft, pleasant sound to the autumn landscape. Rightfully named the quaking aspen (Populus tremuloides) – this deciduous tree has the widest natural range of any in North America, stretching from the foothills to the subalpine zone, typically found in ravines and valley bottoms.

Aspen are easily identifiable by their narrow trunks covered in smooth greenish-white bark. Although the aspen loses its leaves in the fall, there is chlorophyll in the bark – easily seen after scratching the bark. This allows the tree to continue to photosynthesis during the winter months. The tree is a sun loving, shade intolerant species. As the aspen grows larger, creating a canopy of shade, it will self-prune branches leaving behind black markings almost always in the shape of an eye.

Some ecologists will argue that aspen holds the title of the largest living organism. This is because aspen grown in stands, called clones and reproduce primarily through sending up sprouts from their roots. This means that virtually all the trees in a clone are connected and genetically the same. The fall is one of the only times of year one can tell the difference between multiple stands. Members of one clone will all have the same shade of color transitioning from green to yellow at the same time. By examining this different color patchwork along a mountainside you can distinguish individual clones from each other.

Dana Andersson | University of Montana | Geography Department