by Deborah B. Hill and John R. Shelly *
*This publication is based on an earlier version of FOR-2 published
in 1960 by James A. Newman.
Yellow-poplar (Liriodendron tulipifera)
is common throughout the United States east of the Mississippi River. Although
called "poplar" this species has no biological relationship to the true
poplar genus, Populus.
Yellow-poplar was probably named because
of the yellow color of the wood from old trees. Also called "tuliptree"
or "tulip-poplar" because of the flower and leaf shapes, it is one of only
two species of the Liriodendron genus which survived the last Ice Age.
(The other species is a native of China.)
American pioneers found yellow-poplar
trees as tall as 190 ft and up to 10 ft in diameter which they cut for
house timbers and other purposes; today trees taller than 150 ft or larger
than 3-4 ft in diameter are seldom seen in the second-growth forest. Yellow-poplar
is native to all of Kentucky, but is most common in the eastern part of
The outstanding physical characteristics
of yellow-poplar are its tulip-shaped
leaves, its yellow-orange, tulip-like flowers and the straightness
of its bole. The trees grow both tall and straight, easily attaining heights
of 80 to 100 ft and often are clear of lateral branches for two-thirds
or three-quarters of that height. The bark is thin in the early years of
growth, but develops a thick ridged appearance in later years, marked with
distinctive white areas between the ridges. The winged seeds (samaras)
are similar to those of maple trees, but the samaras are clustered together
in upright fruiting bodies that resemble conifer
are 5-6 in. long and wide, and their truncated tips distinguish them from
any other kind of leaf. Alternately arranged along the twigs, they are
smooth-edged and usually four-lobed. Dark green during the growing season,
they turn yellow in the fail, while in spring, pale green new foliage is
among the first visible. In the winter, the buds are reddish purple and
are shaped something like a duck's bill or cupped folded hands. The tulip-like
flowers usually appear in May.
Yellow-poplar trees have few insect
or disease problems. There are four major insect pests: the tuliptree scale,
the yellow-poplar weevil, the root-collar borer and the Columbian timber
beetle. The first two feed on buds, leaves and twigs, while the latter
two bore into the wood. None is fatal, but they will cause stress to the
trees and the latter two reduce the wood's value by degrading its quality.
Several fungal diseases affect yellow-poplar;
most are rots of one kind or another (e.g., heart-rot, stem canker). Although
these factors may cause death, they more commonly stress the trees' biological
activities or degrade the quality of the wood.
Yellow-poplar wood currently in use
has very little natural resistance to attack by the common wood destroying
fungi (decay) and boring insects (termites, carpenter ants, etc.). The
wood should be treated with a wood preservative whenever it is used in
high hazard conditions such as ground contact or places where it will remain
moist for extended times.
Fire is a serious problem for yellow-poplar,
particularly in young stands when the bark is still thin and easily damaged.
Even a light fire will permanently scar seedlings or saplings.
Grazing animals, either wildlife or
livestock, also pose serious problems for yellow-poplar. If the animals
do not kill seedlings and saplings outright by feeding on them, they affect
tree growth by trampling the seedlings or by compacting the soil around
the tree roots, thus restricting healthy root growth.
Vines, including grape, Japanese honeysuckle
and kudzu, can be very destructive to yellow-poplar trees by growing over
them, shading out the tree crowns, competing for moisture, nutrients and
sunlight, and causing physical damage by breaking off upper tree branches.
Climatic factors can also affect yellow-poplar
adversely. Accumulated ice from ice storms can break the tops of larger
trees. Unusual frosts or frost pocket locations can affect early growth
of seedlings and ultimately cause "shake" where the wood separates along
the annual growth rings when cut.
Management of Yellow-Poplar
A fast-growing tree, yellow-poplar
grows best in deep, moist but well-drained soils along streams and in mountain
coves. It does not grow well in dry, poor soils and in wet, poorly-drained
sites. In the best sites, its height growth out-competes any tree species
associated with it; on poorer sites, it is less competitive with its associates.
Yellow-poplar needs full sunlight to
grow and develop. In dense woods, newly-germinated seedlings will survive
only a few weeks. Harvesting trees by selection cutting, where only a few
trees are removed from a stand, will gradually eliminate yellow-poplar
as a major forest species because this practice does not open up the forest
canopy enough to provide adequate sunlight to seedlings. Forest managers
need to use different forms of harvesting to encourage the establishment
and development of yellow-poplar and similar shade-intolerant species.
Group selection or patch clear-cutting of areas larger than a half-acre
will favor light-demanding trees in the new forest stand.
Since yellow-poplar seeds are wind-borne,
dense stands often become established in abandoned fields. Many pure stands
of yellow-poplar in Kentucky occur on old corn field sites. When the trees
are too closely spaced. tree farmers should cut some of the poorer stems
to give the better quality trees more room to grow, a practice known as
thinning. Remember, however, that making several thinnings over the years
is better than cutting too many trees at one time. When pole-size (4 to
10 in. in diameter) yellow-poplar is mixed with lower value species such
as black gum, removing the trees competing closely with the yellow-poplar
will improve the value of the forest stand.
Yellow-poplar was one of the first
trees to be harvested and sold in Kentucky. Early settlers favored it for
constructing log buildings because of the abundant long, straight logs
available, its relatively light weight and because it seemed to resist
insect attack and decay. Many old yellow-poplar log structures can still
be found around the state. The younger growth logs available today are
not considered to be decay or insect resistant (see Damaging Factors).
Yellow-poplar is not as strong as Douglas-fir
and southern pine, but is stronger than many other softwood structural
species such as spruce, fir and most other pines. It also has excellent
resistance to splitting during nailing and is rated fair in nail and screw-holding
Yellow-poplar is still one of the major
hardwood species utilized today. ln 1977, the estimated harvested log volume
of yellow-poplar was 62 million board feet (Doyle scale) or 15% of the
total hardwood log volume harvested for that year. Because of its favorable
wood properties, it can be used in a wide variety of products. It is generally
described as a straight-grained, medium-textured, diffuse-porous hardwood
with a whitish colored sapwood (outer portion of tree) and yellow-green
heartwood (central portion of tree).
Yellow-poplar is considered a low density
hardwood. The density of the wood when air dried (moisture content of 12%}
is approximately 29 lb/ ft3 which ranks it denser than basswood (25 lb/cu
ft), but less dense than the oaks (40-50 lb/cu ft) and about the same density
as cottonwood (28 lb/cu ft). Because of its low density, yellow-poplar
is moderately soft, light weight and intermediate in strength compared
to other hardwood species. It also has the advantages of machining well
with both hand and power tools and is ranked high in its paintability.
Uses of Yellow-poplar
Bees collect nectar from the yellow-poplar
flowers in the spring and produce large quantities of honey from them.
The foliage, buds, twigs and tender bark furnish food for rabbits, deer,
The main commercial use of yellow-poplar
is in the furniture industry where it is used for parts, core stock and
frames. It is also used to make boxes, crates and pallets for transporting
other products. Another use is in window sashes. door frames, molding and
other trim. Veneer (rotary peeled) is also used as a core ply for some
decorative hardwood plywoods. Low grade yellow-poplar is also a major pulp
species in the state. Other minor products manufactured from yellow-poplar
include mine props, barn lumber, picture frames and wooden toys.
The "favored species" status of yellow-poplar
for building construction by early settlers has been largely replaced by
softwood species from the Southern pine region and the Pacific Northwest
and Canada. Its decline was primarily due to the abusive over-harvesting
practices of the early 1900's which virtually eliminated the large, commercially
desirable trees. Today. however, ample yellow-poplar is available and is
beginning to be used as a structural lumber once again. It has the added
advantage of growing closer to the eastern population centers than the
more common structural species. Although the young growth yellow-poplar
being harvested today has a tendency to warp when sawn into lumber, new
technology has been developed (Saw-Dry-Rip) to overcome this problem. Yellow-poplar
has a strong potential to become a major species for structural purposes
in the future.
A possible future structural use of
yellow-poplar is as a raw material for composition boards such as waferboard,
4 ft x 8 ft panels (similar to plywood} made from wafer-sized wood particles.
The relative abundance of yellow-poplar
in the eastern United States combined with its favorable wood properties
indicate its increasing importance as a commercial species. The present
situation where timber growth is greater than harvesting removals also
assures a future of improving timber value and quality for yellow-poplar.
Allison, Richard C. and E.C. Deal. Grades, Design Values and Span Tables
for Yellow-Poplar Framing Lumber. AG-351. North Carolina Agricultural Extension
Service. Raleigh, NC. 1985.
Beck, Donald E. and L. Della-Bianca. Yellow-Poplar: Characteristics
and Management. U.S. Dept. Agric., Agric. Handb. #583. U.S. Government
Printing Office. 1981.
Marketing and Utilization of Yellow-Poplar. Symposium Proceedings.
University of Tennessee, Knoxville, TN. 1978.