Could Yosemite's iconic "Ahwahnee Meadow Cottonwoods" be Aspen trees instead?

I recently made another series of photos of the Ahwahnee Meadow Cottonwoods in Yosemite Valley. I’ve photographed this cluster of trees, commonly called “The Ahwahnee Meadow Cottonwoods,” many times spanning several years. A few days ago, I posted a new photo of the trees. A friend, a biologist and someone whose opinion I respect, suggested that these trees might actually be Aspen, not Cottonwood. I had often pondered the same question. So, I promised to make a closer inspection upon my next visit to the trees, which just happened to be this week.

This photo was taken on Nov. 2, 2019. By the time I returned to Yosemite Valley on Nov. 13th, most of the leaves had fallen.

Identifying from a distance

The National Park Service understandably prohibits people from tromping through the Ahwahnee Meadow, so I could only study the trees from a distance. I used a long, telephoto lens from my position on the path to get a closer look. A tree’s size, habitat, range, flowers, bark, and leaves are each important clues to its identity, but blossoms are only observable in Spring, and it is currently late Autumn. So, no blossoms. Even so, a few yellow leaves were still clinging to mostly bare branches, which is important for identification.

Cottonwoods prefer wet soil, and will even tolerate standing water for a short time. Aspen prefer drier climate.

Location is a clue

Aspen and Cottonwood are both from the genus Populus, so there are similarities between the two. Although they are cousins and share some general characteristics, there are key differences. Aspen prefer to grow on dry, rocky hillsides, which is why you find them along the Eastern slope of the Sierra Nevada mountain range. Cottonwoods prefer to grow in soils that receive regular moisture, such as near meadows or along rivers banks and streams. Cottonwoods can be found on both the East and West sides of the Sierra. However, Aspen are rarely found on the West side, which receives more precipitation than the dryer Eastern Sierra, where Aspen are much more abundant.

In addition, Aspen grow at higher elevations, from 6,500 to 10,000 feet. Yosemite Valley sits at 4,000 ft. elevation on the Western side of the Sierra. There are a few Aspen groves in the park at higher elevations. They can be found on the Tioga Road and Glacier Point Road along a path near Badger Pass ski resort. As far as I know, there aren’t any Aspen groves in Yosemite Valley.

A close up reveals the mature Cottonwood’s thick, deeply furrowed bark. The younger trees growing right next to the mature tree don’t have the markings of a mature Cottonwood, but you can see a couple of the youngsters are starting to develop the signature vertical grooves.

Studying the bark

The middle, older tree at the center of the grove is definitely a Cottonwood. It has the signature dark brown, deeply grooved bark that one would expect in a mature Cottonwood. It has a wide crown, with thick, heavy branches.

I’m pretty certain that the surrounding, less mature trees, are also Cottonwood. When they are young, Cottonwood trees have light colored bark with horizontal banding, very similar to Aspen. They don’t develop the darker, vertical-ribbed, thick grooved bark until they are much older. If you look closely, you can see that a few of the trees are starting to transition from the more pale bark to the darker bark with vertical lines.

The Ahwahnee Meadow trees are also missing the signature black “eyes” — sometimes also called “beards” — on their trunks, which is a key field mark of their Aspen cousins.

Although the bark of these trees look similar to Aspen, they are lacking the dark black “eyes” that are a key field mark of Aspen. Young Cottonwoods have horizontal bands too, but they don’t develop vertical grooves until they mature.

These Aspen trees show the signature dark black “eyes” on their trunks. These were growing on the Eastern slope of the Sierra Nevada range, which is drier and rockier than the West side.

Leaves tell the story

The leaves of the trees in the Ahwahnee Meadow are somewhat triangular shaped, which is typical of Cottonwood. Aspen leaves are more round or heart-shaped.