Populus section Aigeiros is a section of three species in the genus Populus, commonly known as cottonwoods. Native to North America, Europe, and western Asia, these large deciduous trees grow 15–30 m tall with thick, deeply fissured bark and distinctive diamond-shaped leaves. Their leaves have a flattened petiole that allows a unique wind movement and lack a balsam scent. Male and female flowers appear in separate catkins before leaf emergence, with seeds dispersed on cottony structures. Exceptionally tolerant of flooding and erosion, cottonwoods are key species in their habitats, with three accepted species distinguished primarily by leaf patterns but sharing the characteristic diamond leaf shape.
Species
Populus deltoides
Eastern cottonwood (Populus deltoides) is one of the largest North American hardwood trees, although the wood is rather soft. It is a riparian zone tree. It occurs throughout the eastern United States, parts of southern Canada, and northern Mexico. The leaves are alternate and simple, with coarsely toothed (crenate/serrate) edges, and subcordate at the base. The leaf shape is roughly triangular, hence the species name, deltoides. Their winter buds are enrobed in a protective, fragrant resin that coats young leaves when they unfurl from the bud.
In the typical subspecies P. d. deltoides (Vermont south to northern Florida and west to about Michigan), the leaves are broad and triangular, 7–15 cm across at the base. Further west (Minnesota south to eastern Texas), the subspecies P. d. monilifera (plains cottonwood; syn. P. sargentii) has somewhat narrower leaves, 5–10 cm wide at the base. This is also the state tree of Nebraska, Wyoming, and Kansas. In West Texas, New Mexico, and Colorado, the subspecies P. d. wislizeni (Rio Grande cottonwood; syn. P. wislizeni) occurs.
Populus fremontii
Fremont's cottonwood (P. fremontii) is native to the southwestern United States and western Mexico.2 In the United States, the species can be found in Arizona, California, Colorado, Idaho, Nevada, New Mexico, Texas, and Utah. In Mexico, it can be found in the states of Baja California, Baja California Sur, Sonora, Chihuahua, Coahuila, Nuevo León, Mexico State, and Puebla.34 It differs from the eastern cottonwood mainly in the leaves having fewer, larger serrations on the edge, and small differences in the flower and seed pod structure. Some taxonomists formerly considered P. fremontii to be a subspecies of P. deltoides.56
Populus nigra
Black poplar (P. nigra) is native to Europe and Western Asia, is distinct in its much smaller leaves, 5–11 cm (2.0–4.3 in) across, with a more rhombic (diamond) shape.
Cultivation and uses
Cottonwoods are widely grown for timber production along wet river banks, where their exceptional growth rate provides a large crop of wood within just 10–30 years. The wood is coarse and of fairly low value, used for pallet boxes, shipping crates, and similar purposes where a cheap but strong enough wood is suitable. They are also widely grown as screens and shelterbelts. Many of the cottonwoods grown commercially are the hybrid of eastern cottonwood and black poplar, Populus × canadensis (hybrid black poplar or Carolina poplar).
Cottonwood bark is often a favorite medium for artisans. The bark, which is usually harvested in the fall after a tree's death, is generally very soft and easy to carve.
Cottonwood is one of the poorest wood fuels; it does not dry well, and rots quickly. It splits poorly, because it is very fibrous. It produces a low level of energy per unit of volume of wood.7
Cottonwoods serve as food for the caterpillars of several Lepidoptera.
External links
- Minnesota DNR big tree list. The largest tree by circumference in Minnesota is a Populus deltoides at 394 inches (1,001 centimeters) measured at the trunk 4 and 1/2 feet (137 cm) above the ground. This tree is 106 feet (32.31 meters) tall.
- Monster Ohio Cottonwood - 528 points in 2005 on YouTube
References
Isebrands, Jud G.; Richardson, Jim (February 12, 2014). Poplars and Willows: Trees for Society and the Environment. CABI. ISBN 978-1-78064-108-9 – via Google Books. 978-1-78064-108-9 ↩
"Populus fremontii (Fremont cottonwood)". Calflora Database. http://www.calflora.org/cgi-bin/species_query.cgi?where-taxon=Populus+fremontii ↩
"Populus fremontii". Germplasm Resources Information Network. Agricultural Research Service, United States Department of Agriculture. Retrieved 12 December 2017. https://npgsweb.ars-grin.gov/gringlobal/taxonomydetail.aspx?id=404966 ↩
"Populus fremontii (Fremont's cottonwood)". USDA Plants Profile. https://plants.usda.gov/plant-profile?symbol=POFR2 ↩
Schneider, Al. "Populus deltoides". Wildflowers, Ferns, and Trees of Colorado, New Mexico, Arizona, and Utah. http://www.swcoloradowildflowers.com/Tree%20Enlarged%20Photo%20Pages/populus%20deltoides.htm ↩
"Populus". North American Plant Atlas. BONAP. Archived from the original on 2012-04-25. https://web.archive.org/web/20120425154646/http://bonap.org/BONAPmaps2010/Populus.html ↩
Sweep's Library: Firewood Comparison Charts Archived 2006-08-13 at the Wayback Machine The Chimney Sweep. http://www.chimneysweeponline.com/howood.htm ↩