Tree Eye on a Quaking Aspen tree trunk in Grand Teton National Park, Wyoming - Photos

Aspen tree eyes are dark markings on main trunk of the trees where side branches used to be. Quaking aspen are shade-intolerant and as they grow taller lower branches become shaded. The tree cut off the flow of nutrient (sap) to these lower branches to conserve energy making these branches fall off eventually. These leave a mark looking like dark eyes.