Trees of Yellowstone National Park
Trees can be defined as woody, single-stemmed plants that reach over 33 feet at maturity. Their large size renders them the most conspicuous plants in the landscape. Yellowstone National Park is home to both coniferous and broadleaf species. At Yellowstone, all conifers (except the larches) are evergreen and retain their needles or scale-like leaves for more than one growing season. The larches have deciduous, needle-like leaves that turn bright yellow or orange in the autumn and fall from the tree. All broadleaf trees in Yellowstone are deciduous. Many provide dazzling autumn contrasts of yellow and orange against the background of dark green conifers.
Coniferous trees are most widespread in the park because of the high altitudes and short growing season. Lodgepole pine is by far the most common, but douglas fir, subalpine fir, engelmann spruce, blue spruce, and whitebark pine can also be found. Some hardy deciduous trees such as cottonwood and aspen can be found as well.
Whether alive, dead or decaying, trees provide habitats for many different forms of life. They were also (and are still) integral to aboriginal and other people as sources of food, medicines, tools and shelter.
The following are some of the more common coniferous and deciduous trees found in Yellowstone.
Conifers of Yellowstone
Lodgepole pine (Pinus contorta var. latifolia)
The Lodgepole pine is the most common tree in Yellowstone and grows long and straight, reaching up to 75 feet in height, and covering as much as 80 percent of the park. When they grow in thick groves, only the tops of the trees have branches since only the tops are able to access direct sunlight. The Lodgepole pine can be differentiated from all other Rocky Mountain pines by its needles, which are borne in bundles of two. Lodgepole pines rarely live for more than 300 years, and are abundant in places such as Yellowstone, where forest fires are common.
Unlike the ponderosa pine and the western larch, which are also common in the area, the lodgepole pine has a thin bark and is easily killed by fire. The lodgepole pine has adapted to this environment by producing cones sealed shut by a resin that must be melted before the seeds are released. Thus, the lodgepole pine actually depends on fire for its ability to reproduce. A tremendous amount of seed is stockpiled between fires to re-populate burnt areas.
The Native Americans around Yellowstone used the trees to make fishing spears and poles for constructing their dwellings and teepees. Furthermore, the sweet and juicy inner bark, which can be harvested in late May or June when the sap is running, was an important food source. Traditionally, it was usually eaten fresh although sometimes it was also dried to be eaten later. Some Native Americans also used the pine bark in a remedy for coughs and tuberculosis.
Douglas Fir (Pseudotsuga menziesii)
The douglas fir is actually a member of the pine family, with prickly cones and a dark, deeply etched bark. This tree, which prefers the north-facing side of mountains, has flat, flexible, single needles growing around the branch, giving it an appearance of fullness. Douglas fir cones hang downward and do not disintegrate in the air, but fall to the ground whole, littering the forest floor. This is another indication of its close relationship to pines. The douglas fir’s thick bark and tall, clear bole help protect it from fires. The great many seeds produced by this tree support large populations of small mammals and birds. Many Yellowstone mule deer rely on it for both food and shelter.
The Aboriginal people made tea from its young twigs and needles. The sap, as in other conifers was used for treating colds, and the seeds were eaten for sustenance. The boughs played a role in many ceremonial functions, including mourning, sweat lodges and the washing of twins. The boughs were also used as bedding.
Subalpine Fir (Abies lasiocarpa)
Subalpine fir is the most widespread true fir in western North America, and is the smallest of western true firs. The needles sprout individually from the branches of this tree. The cones grow upright on the branches, and instead of falling off, as do most coniferous cones, they dry up on the branch itself, and eventually blow away.
Look for the slender, conical crown of this tree. When heavy snows weigh down the lower branches, they often become rooted, forming a circle of smaller trees called a snow mat. This process, also called ‘layering,’ contributes to the development of small clusters of trees at the tree line. Subalpine firs are typically found at high elevations near the timberline.
Native Americans used subalpine fir extensively for medicine. The sap was extracted to take away blisters and to cure tuberculosis, and the bark was boiled to make a cough syrup. The sweet smelling boughs were also used as bedding and a wash.
Engelmann Spruce (Picea engelmannii)
This tree can also be found at the higher elevations, growing in shaded ravines and in the canyons of the Teton Range above 6,800 feet and sometimes much higher. It is abundant near Kepler Cascades, Spring Creek, and the south entrance of Yellowstone National Park. It can be distinguished by single needles that are square and sharp to the touch, and by cones with papery scales that are approximately 1.5 inches long.
The engelmann spruce is a long-lived tree, with a lifespan of up to 1000 years, and is also one of the world’s most cold-tolerant species. It was used by the Aboriginal people in several ways. The split roots were used for sewing baskets and bark canoes, and the pitch was used as a poultice for sores and slivers. Emerging needles were also chewed for coughs.
Blue Spruce (Picea pungens)
The engelmann spruce's cousin, this tree is most commonly found along the Snake River near Jackson. True to its name, it is characterized by its bluish appearance. It has stiff, sharp needles and cones that are twice the size of the engelmann's.
The blue spruce is renowned for its unique silver or blue-green color and even tapering shape. The silvery appearance is due to a fine white powder on the surface of young blue-green needles.
It is never abundant and usually grows below the engelmann spruce in subalpine areas. It clearly favors moist locations, but actually is drought resistant and can survive extremes of temperature.
Whitebark Pine (Pinus albicaulis)
Whitebark pine is unique among native pines in that its cones do not open until they disintegrate at maturity. Its seeds are heavy and wingless, falling near the base of the tree. Seed dispersal depends on the Clark’s nutcrackers, which in turn depend on the seeds for food. Many mammals, including grizzly bears and red squirrels also eat the seeds.
Native Americans harvested the seeds in autumn, roasting the cones overnight in pits before removing the seeds. They would then crush the seeds and either mix them with berries or pound them into flour. The fibrous roots of the tree were also used to sew bark together and to weave watertight containers and canoes.
Currently, whitebark pine is imperiled throughout its range by a host of different factors including white pine blister rust, an introduced pathogen; the endemic mountain pine beetle; and the changing climate and fire regimes.
Deciduous Trees Of Yellowstone
Aspen (Populus tremuloides)
The aspen is the most common broad-leaved tree in the park, though willow and cottonwood are also found. Aspen forests are not extensive in the area, but because of their white bark and bright green foliage, which becomes brilliantly yellow in the autumn, they are conspicuous.
The elimination of the gray wolf in the early part of the 20th century created a major disturbance in the existent ecosystem, resulting in the populations of elk and other large prey animals soaring out of control. These animals fed on new growth vegetation, including upland aspen and riparian cottonwood, which suffered greatly from over-grazing.
The resulting imbalance also affected the habitats of many other plant and animal species throughout the park. In recent years, with the reintroduction of wolves into the park, these trees have been making a comeback, and the whole ecosystem is in the process of regaining its previously lost balance.
Aspen reproduce primarily from root suckers following disturbances such as cutting or fire. Some Native Americans used rotten aspen wood as a diaper material and as a lining for baby cradles. Aspen provide important habitats for a number of wildlife species. Beavers feed on the bark and shoots, and cut down trees to construct dams and lodges. Several bird species nest in cavities of old or dead aspen. The Native Americans also used the cottony seed fluff of the aspen as stuffing for pillows. The inner bark was used to make soap and medicinal tea.
Cottonwood (Populus balsamifera ssp.)
Mature cottonwoods have a rough, thick, grey bark and large leaves that turn a beautiful gold in the fall. Greater Yellowstone has three types of cottonwoods, the black, narrowleaf and plains.
Black cottonwood can be found on the highest elevations, in the foothills and mountains, plains cottonwood grows at the lowest elevations, and narrowleaf is in between. The narrowleaf has lance-shaped leaves, while the others have larger heart-shaped ones. Narrowleaf dominates the upper Yellowstone River Valley in the park and Paradise Valley north of there. The lower Yellowstone has plains cottonwood. Narrowleaf is the common riparian tree around Jackson Hole.
Cottonwood is an important stabilizer of riverbanks, and it maintains river islands and enhances fish habitats. Along streams, it provides shade, which keeps water temperatures low, and its decaying leaves provide a rich source of nutrients for caddis flies, mayflies and other insects – the food of young salmon and trout. Its twigs and buds also provide food for deer, moose, and elk. Beavers prefer eating the inner bark and use the stems to construct dams. Woodpeckers nest in cavities in the trunks of old and decaying or dead trees.
Cottonwoods rarely exceed 200 years in age. They are the one of the area’s largest and fastest growing (up to 6.5 feet per year) broadleaf tree.
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