Photo Credit
Photo courtesy of Rocky Mountain National Park, NPS.

Quaking aspen

Scientific name
Populus tremuloides
Also Known As
Common aspen
Plant Family
Has smooth rounded leaves which flitter in the slightest breeze. It also has bright white or cream colored bark that looks similar to birch bark except that it does not peel.
Identification Hints

Quaking aspen is unique in its smooth rounded leaves which flitter in the slightest breeze, due to the thin flattened stems (petioles) and its bright white or cream colored bark. In the Midwest and northeastern US you can also see bigtooth aspen (Populus grandidentata) which has coarse rounded teeth on the leaf margin, fine hairs on stout twigs, dusty gray buds and brown or green bark. White poplar (Populus alba) is an introducedĀ  tree from Europe that is also similar to quaking aspen but has coarsely toothed leaves that are noticeably dark green above and silvery-white beneath. Poplars and cottonwoods generally have triangular-shaped leaves.

Did You Know?

Quaking aspen is the most widely distributed tree in North America. In Minnesota, Wisconsin, and Utah quaking aspen occupies more land than any other forest type. Stands of quaking aspen are good firebreaks, often dropping crown fires in conifer stands to the ground when they reach aspens and even sometimes extinguishing the fire because of the small amount of flammable accumulation. One male clone in the Wasatch Mountains of Utah occupies 17.2 acres (43 ha) and has more than 47,000 stems! Although individual ramets /trees of a clone may be short-lived, the clone may be long-lived.

Leaves
Leaves are simple, deciduous, broadly oval-shaped to nearly round, 1.5 to 2.5 in (3.8 to 6.4 cm) long with small, rounded teeth on the margins. They have a slender, flattened petiole (leaf stems) and are dark green and shiny above, pale green below, turning yellow, orange, gold, or reddish after first frosts.
Flowers
Male (staminate) and female (pistillate) flowers are on separate trees. Each flower is borne in pendent catkins (they resemble soft caterpillars hanging from twigs). Flowering requires sustained air temperatures above 54Ā°F for about 6 days. Female trees generally flower and leaf out before male trees.
Fruits
Catkins are 2 to 5 in (5 to 13 cm) long, strings of small, light green capsules. Capsules are small, tufted, white, one-celled, each with 6 to 10 brown seeds. Seeds are surrounded by tufts of long, white, silky hairs. Water and wind disperse the seeds. Catkins appear from mid-March to June and mature in about 4 to 6 weeks. Seeds begin to disperse within a few days of ripening.
Bark
Typically smooth, greenish-white to gray-white, thin and peeling, becoming thicker and furrowed with age, especially toward the base. Large trees can have black cracks near the base.
Habitat
Quaking aspen occurs in a variety of habitats and a great range of elevations. It characteristically forms pure or mixed stands with Bigtooth aspen in eastern North America, and with Balsam poplar or Narrowleaf cottonwood in the west. It is common in dry and moist woods, but cannot tolerate shade. Quaking aspen occurs along stream sides, slopes near valley bottoms, dry mountainsides, high plateaus and mesas, talus, openings and slopes in montane and subalpine forests and woodlands. It is a pioneer in disturbed sites with bare soil.
States
AK, AR, AZ, CA, CO, CT, DE, IA, ID, IL, IN, MA, MD, ME, MI, MN, MO, MT, NC, ND, NE, NH, NJ, NM, NV, NY, OH, OR, PA, RI, SD, TX, UT, VA, VT, WA, WI, WV, WY