Populus is a family of trees that includes poplars, cottonwoods and aspens. There are approximately 15 Populus species native to North America, as well as species introduced from other countries as ornamentals, according to "Trees of North America." The poplars share traits such as broad, toothed leaves that develop alternately along the branches. Poplar leaves feature long stems, possess female and male flowers on separate trees, and their seeds have soft cottony tufts attached.
Bigtooth aspen (Populus grandidentata) is a short-lived poplar that experiences rapid growth during its initial 30 years, notes the National Forest Service. Native to southeastern sections of Canada, the Northeast and the Great Lakes States, bigtooth aspen prefers moist soil and grows to 70 feet. Frequently found in river bottoms and near waterways, bigtooth aspen has large leaves, up to 4 inches long, with obvious serrated edges. Bigtooth aspen serves as a shade tree and lawn tree, but the University of Connecticut Plant Database warns to keep it away from areas such as driveways and sewers, because the root system can cause damage as it expands.
The smooth white bark of a white poplar (Populus alba) gives the species ornamental quality. Native to Europe as far east as Siberia, white poplar grows to 100 feet. The poplar is hardy as far north as U.S. Department of Agriculture planting zone 3 and sheds its leaves in the fall after they turn yellow. White poplar hybrids include Globosa,' 'Riucjardii' and 'Pyramidalis.' Plant your white poplars in full sun locations in moist loam. The tree tolerates salt and dry conditions. White poplar can become invasive if it escapes cultivation, growing along roadsides, and in woodlands and open spaces.
Fremont cottonwood (Populus fremontii) is native to the Southwest, typically growing near water, according to the U.S. Department of Agriculture's National Resources Conservation Service. The tree grows to 100 feet near a reliable water source, but typically is smaller, in the 50 to 75-foot range. Fremont cottonwood’s bark is smooth on immature individuals, but develops ridges and furrows as the tree ages. Fremont cottonwood’s dependence on water makes it useful as a landscaping tree only when you have plentiful water available to support it. Fremont cottonwood foliage normally turn shades of yellow, but abruptly lower temperatures can cause the tree to drop its foliage before it turns.
The eastern cottonwood (Populus deltoids) routinely grows to massive sizes in the eastern half of the nation. Some trunks may easily exceed 4 feet in diameter, according to the "National Audubon Society Field Guide to Trees." Eastern cottonwood grows to 80 feet, possessing a broad-spreading canopy, giving the tree a vase silhouette. Eastern cottonwood’s trademark feature is its seeds, which develop in capsules on the branches that burst open in late spring or early summer. The seeds then cover the surrounding area as they drift on the wind, buoyed by the white hairs attached to them.