Culture
Best grown in rich, humusy, consistently moist, well-drained soils in full sun. In the wild, this tree grows in a large variety of soils ranging from rocky soils at high mountain elevations to clay or sandy loams at lower elevations. This tree thrives in cool northern climates, but will struggle in the heat and humidity of a typical St. Louis summer. Generally intolerant of urban pollutants. In the wild, aspens typically appear in groupings or groves, with all of the stems in a grouping being clones rising from a single extensive underground root system. Large groves featuring hundreds of clones may have all originated from a single stem. Trees are dioecious, so each grouping consists of all male clones or all female clones.
Noteworthy Characteristics
Populus tremuloides, commonly called quaking aspen, is perhaps most noted for its beautiful white bark, its deep green foliage that quakes in the slightest breeze and its golden yellow fall foliage color. It has the widest geographical distribution of any North American tree, being indigenous to Alaska and most of Canada, the Pacific Northwest, New England, the Great Lakes and south in the Rockies to New Mexico and Arizona. It is a medium sized deciduous tree that typically grows 20-50’ tall with a narrow, rounded crown. Ovate-triangular to nearly round, dark glossy green leaves (to 3” long) are finely toothed. Leaves flutter in even the smallest amount of wind due to flattened leaf stalks. Leaves turn a beautiful golden yellow in fall. Aspens are dioecious, with male and female flowers appearing in separate catkins on separate clones in spring (April in St. Louis) before the foliage. Catkins are gray-green and not showy. Small drooping fruiting clusters follow the female flowers in late May. Bark of young trees is smooth and greenish white. As the tree matures, bark becomes more chalky white with black warty patching.
Genus name comes from the Latin name.
Specific epithet means resembling the trembling poplar.
Problems
Aspens are susceptible to a large number of disease problems, including dieback, leaf spots, rusts, powdery mildew and cankers. Diseased trees often suffer premature leaf drop as a result thereof. Common insect visitors include caterpillars, borers, aphids and scale. Trees stressed by St. Louis summers are particularly susceptible to diseases such as dieback and to borers.
Uses
A beautiful tree for cool summer climates. Not recommended for the St. Louis area.