Populus deltoides, the eastern cottonwood or necklace poplar, is a species of cottonwood poplar native to North America, growing throughout the eastern, central, and southwestern United States as well as the southern Canadian prairies, the southernmost part of eastern Canada, and northeastern Mexico.
Cottonwood trees (genus Populus) are named for their seeds, which are covered with fluffy, cotton-like fibers. These fibers help the seeds disperse over long distances by wind, resembling cotton tufts, especially in late spring and early summer. Cottonwood trees are male and female, and only the female types form seeds (and cotton).
Cottonwood leaves are triangular, with a flattened petiole that causes them to flutter in the wind. The leaves are green on top and whitish-green underneath. In the fall, the leaves turn yellow. Young cottonwood trees have smooth, gray bark that becomes deeply furrowed and dark gray as the tree ages.
Cottonwoods are found in riparian areas, such as riverbanks, streams, and wetlands. They prefer moist, well-drained soils but can also tolerate drought and flooding. They are among the tallest and fastest-growing hardwoods in North America, adding up to seven feet in height every year. In areas with enough space, such as a ranch or acreage, a cottonwood makes a beautiful addition to a landscape.
Cottonwood wood is relatively soft and light, making it suitable for pulp and paper production. It is also used for pallets, boxes, and crates. The tree’s fast growth rate and ability to stabilize soil make it a popular choice for reforestation and erosion control projects.
Cottonwood trees are hardy and can grow in a wide range of USDA Hardiness Zones, typically from Zone 2 to Zone 9, depending on the species. This means it can tolerate temperatures as low as -40°F to as high as 20°F.
Characteristics of Cottonwood Trees
- Leaves: Cottonwood leaves are generally broad, with a simple, alternate arrangement. They have a flat petiole (leaf stalk), which causes the leaves to tremble or flutter in the wind.
- Flowers and Seeds: Cottonwoods are dioecious, meaning male and female flowers are on separate trees. The male flowers produce pollen, while the female flowers develop into seed capsules that release the cottony seeds in late spring to early summer.
- Growth Rate: Cottonwoods are among the fastest-growing trees in North America, capable of adding several feet in height each year. This rapid growth makes them valuable for quick shade and timber but can also lead to weaker wood prone to breakage.
- Wood: The wood of cottonwood is relatively soft and lightweight, suitable for pulpwood, plywood, and other industrial uses. However, it’s not as durable or strong as hardwoods like oak or maple.
Species of Cottonwood
Eastern Cottonwood (Populus deltoides)
- Habitat: Commonly found in the central and eastern United States, particularly along riverbanks and floodplains.
- Appearance: These trees can reach heights of 70-100 feet or more, with a broad, spreading canopy.
- Bark: Young trees have smooth, greenish bark that becomes deeply fissured and gray with age.
- Leaves are triangular with a broad base, dark green in summer, and yellow in fall
- Male catkins are reddish-purple, and female catkins are green, releasing cotton-like strands with seeds
Black Cottonwood (Populus trichocarpa)
- Habitat: Native to the western United States and Canada, especially along streams and moist areas.
- Leaves may have an ovate shape, and mature leaves may show a light rust color or blotches of brown
- Appearance: This species can grow taller than eastern cottonwood, often exceeding 100 feet. The leaves are more elongated and lance-shaped.
- Bark: The bark is dark gray and deeply ridged.
Fremont Cottonwood (Populus fremontii)
- Habitat: Occurs in California, east to Utah and Arizona, and south into northwest Mexico.
- Named after 19th-century American explorer John C. Fremont
- Appearance: It grows to about 40-80 feet, with a more irregular crown. The leaves are heart-shaped and shiny green.
- Bark: Rough and deeply furrowed, often lighter gray in color.
- Similar to the Eastern Cottonwood but with fewer, larger serrations on the leaf edge and differences in flower and seed pod structure.
Planting and Care Considerations by Zone
- Zone 2 to 3: In these colder zones, cottonwoods can withstand harsh winters. Eastern and plains cottonwoods are particularly hardy and can establish quickly in the short growing season.
- Zone 4 to 7: These zones provide optimal growing conditions for most cottonwood species, with moderate winters and warm summers. Black, Fremont, and narrowleaf cottonwoods thrive here, especially in riparian habitats.
- Zone 8 to 9: In the warmer zones, cottonwoods can grow rapidly, but they may require additional water during dry periods. Eastern and black cottonwoods perform well, with proper irrigation and care to ensure healthy growth.