Everything about The Cottonwood totally explained
The
cottonwoods are three species of
poplars in the section
Aegiros of the genus
Populus, native to
North America,
Europe and western
Asia.
The name is also commonly used for any species of poplar in the
United States, including some poplars not in the section
Aegiros, notably the Swamp cottonwood
Populus heterophylla (in the section
Leucoides) and the Black and Narrowleaf Cottonwoods
P. trichocarpa and
P. angustifolia (
balsam poplars in the section
Tacamahaca).
Those in section
Aegiros are large deciduous
trees 20-45 m tall, distinguished by thick, deeply fissured
bark, and triangular-based to diamond-shaped
leaves, green on both sides (without the whitish wax on the undersides of balsam poplar leaves), and without any obvious balsam scent in spring. An important feature of the leaves is the petiole which is flattened sideways, so that the leaves have a particular type of movement in the wind. The
aspens (
Populus section
Populus) share this characteristic, but not the balsam poplars.
Male and female
flowers are in separate
catkins, appearing before the leaves in spring. The seeds are borne on
cottony structures which allow them to be blown long distances in the air before settling to ground.
The cottonwoods are exceptionally tolerant of
flooding,
erosion and flood deposits filling around the trunk.
In the past up to five or six species were accepted, but recent trends have been to accept just three species, treating the others as subspecies of
P. deltoides.
The
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 and just into southern
Canada. 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.
In the typical subspecies
deltoides (
Vermont south to northern
Florida and west to about
Michigan), the leaves are broad triangular, 7-15 cm across at the base. Further west (
Minnesota south to eastern
Texas), the subspecies
molinifera (
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 western Texas,
New Mexico and
Colorado the subspecies
wislizeni (
Rio Grande Cottonwood; syn.
P. wislizeni) occurs.
The
Fremont Cottonwood Populus fremontii occurs in
California east to
Utah and
Arizona and south into northwest
Mexico; it's similar to Eastern Cottonwood, differing mainly in the leaves having fewer, larger serrations on the edge, and small differences in the flower and seed pod structure.
The third species,
Black Poplar Populus nigra, native of Europe and western Asia, is distinct in its much smaller leaves, 5-11 cm across, with a more rhombic (diamond) shape; see the link for further details.
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, where a coarse but cheap and strong wood is suitable. They are also widely grown as screens and shelterbelts. Many of the cottonwoods grown commercially are the
hybrid between Eastern Cottonwood and Black Poplar,
Populus × canadensis (
Hybrid Black Poplar or
Carolina Poplar).
Felling a cottonwood tree usually involves making an initial deep chainsaw cut to drain the water.
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 woods to use as
Wood fuel. It doesn't dry well, and rots quickly. It splits poorly, because it's very fibrous. It produces the lowest
BTUs per
cord of wood
(External Link
).
Cottonwoods serve as food for the
caterpillars of several
Lepidoptera. See
List of Lepidoptera that feed on poplars.
Further Information
Get more info on 'Cottonwood'.
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