JACKSON, Wyo. — Welcome, October! As autumn weather settles across Jackson Hole, a magnificent display of colorful foliage can be seen all over the valley.
The National Weather Service shared a helpful infographic on social media this week to help explain the chemistry that makes leaves change colors at this time of year.
In short, warm days combined with colder nights lead to the change of hue. Sugars are produced by the leaves in the warm sunshine, but the cold overnight temperatures gradually close a leaf’s veins, preventing the sugars from spreading.
Similarly, the National Park Service details the chemical breakdown on its website.
“Chlorophyll breaks down and the green color disappears allowing other pigments to become visible like carotenoids that produce brilliant yellow and orange leaves,” the park service writes. “Some leaves will generate red pigments, anthocyanins, due to excess water and sugars. Temperature and moisture control the intensity and duration of the colors.”
In the coming months, keep an eye out for these spectacular leaves in Grand Teton National Park and across the valley. The following information was provided by the National Park Service:
Quaking Aspen: These most commonly change to shades of yellow in the fall. Orange and red leaves occasionally occur, but are less common than yellow. Depending on the season, aspens can retain their color for several weeks. Stand health plays a role in whether the trees display strong colors and retain leaves later into the fall. Unhealthy aspen stands are less likely to have vibrant colors whereas a healthy stand will have bright colors. These leaves are usually one to two inches across, their trees have white bark and grow in large stands.
Quaking aspens grow throughout Grand Teton. Look for them near water, on mountain slopes or tucked in with evergreens. Aspens tend to ‘quake’ or ‘dance’ when the wind blows through them. In autumn the trees appear to shimmer as sun dances off their yellow leaves.
Where to find them: Willow Flats Overlook, Snake River Overlook, Oxbow Bend and Two Ocean Lake.
Narrowleaf Cottonwood: Narrowleaf cottonwoods turn bright yellow during the fall. As the leaves change color and fall off, cottonwoods begin a “hardening” process. Chemistry inside of the tree changes so that water is removed from cells to the intercellular spaces. There it can freeze without damaging living cells. Inside the cells there is less water and more sugar, which makes freezing far less likely.
These leaves are usually two to five inches long, the bark is yellowish-green to grayish brown, smooth on upper portions and furrowed into broad, flat ridges on older lower portions.
Where to find them: Cottonwoods are native to wetland and riparian areas and can be found along the banks of streams and rivers. They are present around the Gros Ventre River, Cottonwood Creek and Schwabacher’s Landing.
Black Hawthorn: The black hawthorn grows as a large shrub or small tree. In summer, the plant bears fruit that often attracts birds and other wildlife. Fan-shaped leaves turn to shades of red during autumn.
These leaves are usually one to two inches long, their bushes grow six to 30 feet tall and have 0.5 to one-inch thorns.
Where to find them: Black hawthorn can be found in most moist areas along streams, or in an open area that receives full sun. Look for them at lower elevations in the park. They can be seen around Moose-Wilson Road and Laurance S. Rockefeller Preserve.
Willow: Willows grow in tall bushes around the park. They are a dense plant and grow close together, making them an ideal spot for wildlife to hide. Elk and moose rely on willow as an important food source, consuming their leaves in the summer and stems during the winter months. Long leaves grow green in the summer, but turn to shades of yellow and orange in the fall.
These leaves can be two to five inches long and their bushes grow seven to nine feet tall and wide.
Where to find them: Willows grow in damp, marshy areas. Look for them near springs, around ponds and in areas of low elevation. When viewed from above, their colorful leaves appear to create a bright carpet across the valley. They can be seen at Blacktail Ponds Overlook, Willow Flats Overlook and Christian Ponds.
