The Aspen Tree of Western North America

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Introduction To the Aspen Tree

The white and black trunks of Aspen trees in a forest. — Hansrico Photography / Getty Images

An aspen tree is the most widely distributed tree species in North America, ranging from Alaska to Newfoundland and down the Rocky Mountains to Mexico. Interestingly, Utah and Colorado is home to the largest portion of the natural acreage of aspen in the world.

Aspen trees are described as an all-important and community-dependent "keystone species" within its natural range. Aspen trees are the most visible of western North American hardwoods providing understory biodiversity, wildlife habitat, livestock forage, specialty forest products, and highly desirable scenery.

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Description and Identification of an Aspen Tree

A green Aspen leaf against a hand in sunlight. — Zen Rial / Getty Images

Common names of the tree are trembling aspen, golden aspen, quiver-leaf aspen, small-toothed aspen, Canadian aspen, quakie and popple. The habitat of Aspen trees occurs in pure stands on sandy, gravelly slopes. Aspen is the only transcontinental broadleaf tree growing from Newfoundland to California and Mexico.

Aspen is often associated with the Douglas fir timber type and is a pioneer tree after fires and logging. The tree has the most wind-sensitive leaf of any broadleaf species. The leaves "tremble" and "quake" during moderate winds.

The circular to triangular leaves gives this species its name, each leaf trembling in the slightest breeze at the end of a long, flattened stem. The thin, damage-prone bark is light green and smooth with bands of warty bumps. It has commercial value for furniture parts, matches, boxes, paper pulp.

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The Natural Range of the Aspen Tree

Snow falling on the branches of an Aspen tree. — Pete Lomchid / Getty Images

Aspen trees grow singly and in multi-stemmed clones over the widest distribution of any native tree species in North America.

The aspen tree range extends from Newfoundland and Labrador west across Canada along the northern limit of trees to northwestern Alaska, and southeast through Yukon and British Columbia. Throughout the western United States it is mostly in the mountains from Washington to California, southern Arizona, Trans-Pecos Texas, and northern Nebraska. From Iowa and eastern Missouri it ranges east to West Virginia, western Virginia, Pennsylvania, and New Jersey. Quaking aspen is also found in the mountains of Mexico, as far south as Guanajuato. Worldwide, only Populus tremula, European aspen, and Pinus sylvestris, Scotch pine, have wider natural ranges.

Forest Types of North America

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The Silviculture and Management of an Aspen Tree

aspen trees in autumn — Aspens during autumn along the Changing Canyon Nature Trail in Lamoille Canyon, Nevada. (Famartin/Wikimedia Commons/CC BY-SA 3.0)

"[A]n aspen tree is born of fire, landslide, and disaster. It colonizes disturbed areas, massing at the sunny edges of forests and meadows, where its white bark and gentle grace makes it one of our most highly sought trees for nature photography. It is a montane species in the West, a tree of moist sandy soils in the East and the arboreal emblem in the boreal province of the Yukon..."

"Most individual aspen trees are tall, slender, graceful trees, not known for their massive proportions. Their bark color and branching pattern contribute to the illusion of small size, but aspens can become large on favorable terrain. The largest known quaking aspen is in Ontonagon County at the western end of upper Michigan. It is 109 feet (32.7m) tall and more than 3 feet (.09m) in diameter..."

"Aspen tree seed is difficult to deal with because of its small size and perishable nature. Any damage incurred by establishing aspen trees during transplant ing will doom the trees to cankers, insect attack, bark blemishes, and premature death, so aspens are best established from root cuttings set directly into the permanent planting location." - From Native Trees for North American Landscapes - Sternberg/Wilson

The Silviculture of Aspen Trees

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Insects and Diseases of the Aspen Tree

Damaged leaves on an Aspen tree. — Алексей Tрифонов / Getty Images

Pest information courtesy of Robert Cox - Colorado State University Cooperative extension:

"Aspen trees are affected by numerous insects, diseases and cultural problems. While there are plenty of good-looking aspen around the region, it also is the most common problem tree discussed in calls or samples brought to Colorado State University Cooperative Extension's Plant Diagnostic Clinic..."

"Aspen trees are short-lived trees, as expected from their role in forest ecology. In the urban landscape, even properly cared-for aspen may not reach 20 years. Life spans can be shortened further by one or more of several insects or diseases that attack aspen. Fungal diseases, such as Cytospora or other cankers which attack the trunk, are common, as are diseases of the foliage such as rusts, or leaf spots. Of the many insects that attack urban plantings of aspen, oystershell scale, aphids and aspen twig gall fly are most prevalent."

Remember that aspens are very sensitive to many environmental problems and are host to more than five hundred species of parasites, herbivores, diseases, and other harmful agents. Aspen has been a disappointment to many when planted in the landscape.