Catch a glimpse of "shimmering" Aspen along the Aspen Vista Trail in the Santa Fe National Forest. Photograph by Tira Howard.

ASPEN LEAVES ATTACH TO BRANCHES with long stems, called petioles, that allow them to rotate to catch the sunlight. In aspens, both leaf and petiole are flat, and they join each other at a 90-degree angle, an offset that gives the appearance of “quaking” or “shimmering” in autumn breezes.   

Aspen trees sprout from an underground root system, a single organism that can survive for thousands of years, making aspen groves some of the largest and oldest life forms on earth. A grove in Utah that has been growing for roughly 80,000 years is thought to rank as the very largest, covering 100 acres.