Identifying characteristics:
The white poplar is a fast-growing, short-lived tree with a broad-spreading,
rounded crown growing to 70 feet tall or more, with a similar spread. Leaves are simple, alternate, nearly round
and coarsely-toothed or palmately 3- to 5-lobed. The dark green leaves are
2 to 5 inches long, with a matted coating of long, silvery-white hairs on
the lower surface. They fall early in the autumn, with little coloration
(some may turn yellowish or reddish). Male and female flowers
are produced on separate plants in elongate catkins before the leaves in
spring. Male catkins are cylindrical and 1.25 to 2.25 inches long, releasing
pollen before the leaves are fully grown. Female catkins are narrowly cylindrical
and 2.75 inches long when in fruit. Fruits
are conical, flask-shaped capsules produced in hanging clusters, which release
tiny seeds with cottony hairs that tend to clog air conditioners, vents
and screens in late summer. The small, crescent-shaped leaf scars
each have 3 bundles scars. The ovoid buds are appressed to the twig,
each with the lower scale centered over the leaf scar. Bud scales are shiny
brown with cottony down covering the bud near the base. Lateral buds are
often of two sizes. Bark on young
trees is thin, smooth and greenish-white. Older trunks are deeply furrowed
to form dark ridges near the base.
Similar species:
- bigtooth aspen (P. grandidentata)
Ecology:
Distribution: The white poplar is native from central and southern
Europe to western Siberia and central Asia. It was one if the first poplars
to be introduced to the US in colonial times and has become naturalized.
It is planted throughout Iowa, and is naturalized locally.
Habitat: Hardy from zone 3 to 8, this adaptable species requires full sun and tolerates pollution, a fair amount of salt spray, and is not pH specific. Like most poplars, this species is susceptible to a number of diseases, including cankers, dieback and leaf diseases. Poplar borer, poplar tent caterpillar and scales may be problematic. Trees are easily damaged in storms and continually drop leaves, twigs and debris.
Uses:
Wood: Wood is light, soft and weak. Heartwood is reddish-yellow and
sapwood nearly white.
Wildlife: The native quaking aspen (P.tremuloides) and the bigtooth aspen (P. grandidentata) are important to 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 beavers and porcupines feed on the bark and wood.
Horticulture: This tree is more a liability than an asset in most settings. It spreads aggressively by root suckers and breaks easily in storms, requiring constant maintenance. The roots tend to block drains and sewers, and lift sidewalks. 'Pyramidalis,' the Bolleana poplar, with a narrow, columnar crown, has all the limitations mentioned above. The gray poplar (P. X canescens), hybrid with unlobed leaves, is a hybrid between the white poplar and the European aspen (P. tremula).
