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Populus heterophylla - Swamp Cottonwood
Salicaceae -- Willow family
Height: to 80' Spread: 40-50' Habit / Form: Upright /
Hardy to USDA Zone 3
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Huge Swamp Cottonwood Leaf |
Swamp cottonwood (Populus heterophylla) is of
secondary importance among bottom-land hardwoods.
The species, sometimes referred to as black
cottonwood, river cottonwood, downy poplar, or swamp
poplar, may grow on sites that are too wet for other
native poplars. It is a difficult species to grow
from cuttings, a characteristic that limits its
commercial value. Swamp cottonwood inhabits the wet
bottom lands and sloughs of the Coastal Plain from
Connecticut and southeastern New York to Georgia and
northwestern Florida, west to Louisiana. It grows
north in the Mississippi Valley to southeastern
Missouri, western Tennessee, Kentucky, southern
Illinois, Indiana, Ohio, and southern Michigan.
Though most often found on heavy clays, swamp
cottonwood also grows on the edges of, but not in,
the muck swamps of the Southeast. Optimum growth and
development is in the deep, moist soils of shallow
swamps and low-lying areas near tidewater.
Sites that are too wet for eastern cottonwood
(Populus deltoides) will support swamp cottonwood.
Examples are shallow swamps, sloughs, and very wet
river bottoms where the water table remains near the
soil surface for all but 2 or 3 months in the summer
and early fall. In the southern part of its range,
low, wet flats provide the driest sites occupied by
swamp cottonwood. However, in southern Illinois it
is a dominant or codominant tree on soils with
available moisture varying from 3 to 21 percent for
the 61- to 76-cm (24- to 30-in) layer. |
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Young Swamp Cottonwood, 16 years old
Swamp cottonwood grows naturally on at least
eight major soil types common to the
Midsouth: Alligator, Amagon, Arkabutla,
Forestdale, Perry, Rosebloom, Sharkey, and
Tensas. The soils represent several families
and the orders Alfisols, Inceptisols, and
Entisols. They range from 4.6 to 5.9 in pH
and from 24 to 65 percent clay in the
surface 0.3 m (1 ft).
Flowering and Fruiting- Swamp cottonwood is
dioecious. Flowers are proteranthous,
appearing from March to May. Staminate
catkins are rather stiffly pendant, oblong,
cylindric, and 5 to 10 cm 2 to 4 in) long;
pistillate catkins are 5 to 15 cm (2 to 6
in) long, pendulous, slender, and
raceme-like. Pollination is by wind. Fruits
ripen and the seeds fall from April through
July.
Seed Production and Dissemination- Trees
start seed production at about 10 years.
Reddish-brown obovoid seeds number about
330,700/kg (150,000/lb) (9). Seeds are very
small, light in weight, and tufted with
hairs, features that allow them to be blown
over 100 in (330 ft) by wind and to float
for a considerable distance in water. Water
is an important transporting agent since the
bottom lands normally flood during the
seedfall period. Numerous seeds are produced
annually, but under natural. field
conditions they remain viable for no more
than a week or two.
Seedling Development- Germination is
epigeal. Best seedling establishment is from
seeds that quickly settle on unshaded, moist
mineral soil in shallow swamps, deep
sloughs, and along often-flooded creeks or
rivers. Seedlings require nearly full
sunlight to survive and grow. They also need
an abundance of moisture, especially during
the early part of the growing season.
Seedlings usually occur in groups but seldom
cover a large area (4). Early growth is
relatively rapid but will not match that of
eastern cottonwood. On a well-drained soil
in southern Illinois, swamp cottonwood
seedlings grew at about the same rate as
silver maple seedlings. |
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Swamp Cottonwood Bark |
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Vegetative Reproduction-
Cuttings from juvenile plants will root but
probably not as well as those of eastern
cottonwood (4). Stumps less than 30 cm (12
in) in diameter are likely to produce
sprouts.
Damaging Agents- There are no reported
insect or disease problems associated
specifically with swamp cottonwood. But the
ones that attack eastern cottonwood probably
also damage swamp cottonwood. Important
insect enemies include the cottonwood leaf
beetle (Chrysomela scripta), cottonwood twig
borer (Gypsonoma haimbachiana), poplar borer
(Saperda calcarata), and the cottonwood
borer (Plectrodera scalator). Among the more
important diseases are Melampsora leaf rust
(Melampsora medusae) and a number of canker
diseases, including Septoria, Cytospora, and
Fusarium.
Special Uses - There is no market
specifically for the small volume of swamp
cottonwood harvested. The wood resembles
that of eastern cottonwood and is generally
sold as such. Among the uses for cottonwood
lumber and veneer are boxes, crates, and
interior parts for furniture. Pulpwood is
used in high-grade book and magazine paper.
To date, few other uses have been found for
the species. It is rarely cultivated for
ornament, does not produce important
wildlife food, and is important to flood or
erosion control only in very small,
localized areas. Instead of swamp
cottonwood, a closely related species,
eastern cottonwood, is chosen for planting
because it outperforms swamp cottonwood on
all except the wettest sites.
--USDA Forest Service Fact Sheet
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Swami Ree Kavok
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