Identifying characteristics:
The quaking aspen has a long, straight trunk and narrow, rounded crown at
maturity. It is a rapid-grower, is short-lived (50 years) and grows to 60
feet tall. The 1.5- to 3-inch-long, smooth leaves
are nearly round, with small, irregularly-toothed margins. They are smooth
and dark green above; paler with a whitish bloom underneath. Fall color
is bright yellow. The slender, vertically flattened petioles are up to 3
inches long. They cause the "quaking" or "trembling"
motion that gives the tree its common names. Male and female flowers occur on separate trees in catkins
before the leaves in April. The fruits
ripen 4 to 6 weeks later in the form of flask-shaped capsules which
split into 2 parts when mature, releasing about 10 seeds with cottony hairs.
Leaf scars are semicircular with 3 bundle scars. The ovoid buds
are appressed to the twig, each with the lower scale centered over the leaf
scar. Bud scales are shiny, dark brown and slightly sticky. Lateral buds
are often of two sizes. Young trees have thin, smooth, greenish-white bark with roughened, black, wartlike thickenings.
Older trees become dark brown or gray and furrowed at the base.
Similar species:
- bigtooth aspen (P. grandidentata)
- cottonwoods, eg: White polar (Populus alba)
- paper birch (B. papyrifera)
Ecology:
Distribution: Native from Labrador to Alaska, south to Pennsylvania,
Missouri, northern Mexico and California, this species is the most widely-distributed
North American tree. It is common in eastern Iowa and found scattered along
principal river valleys in southern and western Iowa.
Habitat: Quaking aspens occur on a variety of soils, from moist, loamy sand to shallow, rocky soils and clay, on bottomlands and on upland slopes. An aggressive pioneer plant, it seeds into recently burned sites on exposed mineral soils. It is very intolerant of shade, growing best in full sun on rich, porous limestone soils. Like most poplars, this species is susceptible to a number of diseases which can quickly debilitate trees, including heart rot, cankers, dieback and leaf diseases. Poplar borer, poplar tent caterpillar and scales may be problematic.
Uses:
Wood: Quaking aspen is an important timber tree in Canada and the
northern US. Wood is light, soft and weak, and used for boxes, crates,
pulp, excelsior, pallets, chipboard and matches. It is harvested and sold
with the wood of bigtooth aspen. Quaking aspen is used as a nurse crop for
more valuable timber species.
Wildlife: Quaking aspen and the bigtooth aspen (P. grandidentata) are important native trees for wildlife in the US. Grouse eat the buds and catkins in winter and spring. Rabbits and browsers eat the twigs, tender bark and foliage, and porcupines feed on the bark and wood. Quaking aspen is used by beavers to build dams and is their principal food.
Horticulture: Although this is an ornamental tree, it has a number of drawbacks and is not well suited to landscaping. The root suckers form dense thickets unless controlled; the crown produces very little shade; it is prone to pests and diseases; and the shallow roots extend far from the trunk (to 80 feet).
