Northern Ontario Plant Database
Populus tremuloides Michx.
En: trembling aspen, quiver leaf, quaking aspen
Salicaceae (Willow Family)
General: A fast-growing medium-sized deciduous tree, to 25 m tall. Trembling aspen is shade intolerant, with a shallow wide-spreading root system; it often forms dense clonal populations through root sprouts. Trembling aspen is also a pioneer species that quickly colonizes disturbed soils, cutovers, and burns. Its wood is used extensively in the manufacture of chipboard and plywood.
Stems/twigs: Twigs are greenish-brown to reddish-brown and smooth (glabrous); buds are alternate, scaly, and shiny, with 6—7 dark brown imbricate bud scales. Terminal buds are lanceolate, sharply pointed (acuminate), slightly resinous, and 6—7 mm long. As in all poplars, the smaller lateral leaf buds have the first bud scale positioned directly above the leaf scar, which is elliptic and slightly curved with 3 bundle trace scars. Trunks of younger trees have smooth, non-shredding, greenish-white to light gray bark; mature trees have light to medium gray bark with horizontal ridges and short diamond-shaped furrows; the base of older trees is often deeply furrowed. Lenticels are horizontal and become more pronounced with age.
Leaves: Alternate, simple, palmately-veined with 3 main veins, and long-petiolate. Petioles are 1—6 cm long, often orange to red, and flattened at right angles to the blade, causing the leaves to flutter in the wind. Mature leaf blades are broadly oval to ovate, usually glabrous, and 3—7 cm long and wide. Leaf blades are dark green or gray-green above; lower blade surfaces are pale green. Leaf bases are rounded, very slightly cordate, or truncate; apices taper abruptly to a short point (acute); margins are finely toothed (crenate-serrate), with 18—40 irregular teeth on each side. Leaves turn yellow in autumn.
Flowers: Unisexual, with male and female catkins on different trees (plants dioecious). The densely-flowered catkins are pendant and emerge before the leaves; individual flowers are subtended by bracts with ciliate margins. Both male and female catkins are long and slender. Male (staminate) catkins are 5—7.5 cm long, their flowers have 6—12 stamens; female (pistillate) catkins are 4—10 cm long with an ovoid superior ovary that has 2 carpels and 2 stigmas. Poplar flowers are wind-pollinated. Flower buds are larger than the terminal bud, 6—10 mm long, and occur on lateral second-year branches.
Fruit: Fruiting catkins are 10—12.5 cm long. Each capsule is narrowly ovoid, green, glabrous, and 2.5—4.5 mm long. Poplar capsules split into 2 halves (valves) and have 10—14 seeds, each topped by a tuft of silky white hairs.
Habitat and Range: Open or closed forests on a variety of soils types, talus slopes, cutovers, burns, disturbed ground, and mine tailings. Trembling aspen is a boreal North American species with a trans-Canada range; it occurs throughout the Algoma District.
Similar Species: The largetooth aspen (Populus grandidentata Michx.) is similar in form to trembling aspen, but largetooth aspen has ovate leaves with coarsely dentate margins; immature leaves are densely hairy beneath and the leaves of vigorous shoots are larger with finely serrate margins. Balsam poplar (Populus tremuloides L.) has ovate glabrous leaves with finely serrate margins and a glaucous lower surface, often resin-stained to orange. The buds of largetooth aspen have bud scales with a coating of whitish hairs, while balsam poplar has very resinous buds that are long and sharply-pointed.Back to species list