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Recognizing Important Tree Speciesand Their Products
HOW MANY tree species are there? When
asked, most people respond by saying
they don’t know or they never really thought
about trees being different. Yet, there is a great
diversity of tree species with different
characteristics that lend themselves to different
uses.
Objective:
� Identify important forest tree species.
Key Terms:
�
Important Tree Species
There are many tree species. Forests in one part of the country have different tree species
than forests in other parts of the country. Recognizing that trees are different and that each
type of tree has unique characteristics is important in forestry.
TREE TAXONOMY
Taxonomy is the classification of plants according to natural relationships. Trees are mem-
bers of the plant kingdom and are placed into divisions, classes, subclasses, orders, families,
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angiosperms
dehiscent fruits
dichotomous venation
dioecious
gymnosperms
hardiness
indehiscent fruits
inflorescence
leaf venation
monoecious
palmate venation
parallel venation
pinnate venation
taxonomy
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genera, and species. Carl von Linné (Linnaeus), a Swedish botanist, proposed this system of
classifying plants.
There are two divisions: Pinophyta and Magnoliophyta. Coniferous species make up the
Pinophyta, and the trees in this division are called gymnosperms. Gymnosperms are plants
that bear naked seeds without an ovary. Broad-leaved species make up the Magnoliophyta, and
the trees in this division are called angiosperms. Angiosperms are plants having seeds borne
within a pericarp.
HARDINESS
Hardiness is a plant’s ability to withstand cold temperatures. Hardiness is one of many
factors that affect plant survival in a specific area. Large bodies of water, well-drained soil, wind
protection, and adequate moisture increase plant hardiness.
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Zone 1 Zone 7
Zone 5 Zone 11
Zone 3 Zone 9
Zone 2 Zone 8
Zone 6
Zone 4 Zone 10
Below -50°F 0 to10°F
-20 to -10°F Above 40°F
-40 to -30°F 20 to 30°F
-50 to -40°F 10 to 20°F
-10 to 0°F
-30 to -20°F 30 to 40°F
1
7
2
8
3
4
9
5
10
11
11
6
FIGURE 1. A typical hardiness map.
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A hardiness map is useful in determining the average low temperatures in a given area. Both
the Arnold Arboretum and the U.S. Department of Agriculture publish hardiness maps. Har-
diness ratings are meant only as guides and should not be looked upon as limiting factors in
plant use.
TREE IDENTIFICATION
To identify woody plants successfully requires a working knowledge of taxonomic termi-
nology and concise mental pictures of leaf, bud, stem, flower, and fruit morphology. The leaf,
twig, bark, and fruit are the most commonly used characteristics for tree identification. Each
kind of tree, whether broad leaved or coniferous, has certain characteristics that make it dis-
tinctive from other species.
Leaf Morphology
Most trees can be identified by
the type, size, shape, color, tex-
ture, and arrangement of leaves.
Angiosperms have broad leaves,
while gymnosperms have needle-
like leaves.
Broad Leaves
A broad leaf consists of one or
more leaf blades and a petiole, or
leaf stem. A bud is located where
the leaf and the stem meet. Broad
leaves may be simple or compound. A simple leaf has a single leaf blade. A compound leaf has
multiple leaf blades, known as leaflets. A palmately compound leaf has each leaflet attached at a
common point. A pinnately compound leaf can have either an odd or even number of leaflets
along an extension of the petiole, called a rachis.
The arrangement of leaves and buds can be used as a basis for identification. Leaves are typi-
cally arranged in an alternate, opposite, subopposite, or whorled fashion. The arrangement in
which leaves are spaced in alternating fashion along the stem is known as alternate. An oppo-
site leaf arrangement is characterized by leaves directly across from each other on the stem.
Subopposite refers to a condition in which the leaves are not spaced sufficiently far apart to be
considered alternate, nor are they perfectly opposite. Whorled refers to a condition in which
three or more leaves are present at a node.
The pattern of veins in a leaf is called leaf venation. If the leaf has a prominent central
vein, or midrib, that extends from the base where the petiole attaches to the blade to the apex
of the leaf, the pattern is known as pinnate venation. If several main veins of approximately
equal size extend from the base of the leaf to the apex of the lobes or the margins of the leaf,
the leaf has palmate venation. In dichotomous venation, the basal veins extend for a
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FIGURE 2. This pine tree is classified as a gymnosperm.
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distance and then branch to form a “Y”-type pattern. In parallel venation, the veins run
essentially parallel to each other along the long axis of the leaf.
A tremendous amount of terminology is related to leaf shapes, bases, margins, and apices.
Needle-like Leaves
Needle-like leaves can be of different shapes. Three common shapes are scale-like, awl
shaped, and needle-like. Scale-like foliage overlaps like the shingles on a roof or the scales on a
fish. This type of foliage is relatively soft to the touch. Needles shaped like awls are usually
very sharp to the touch. Needle-like foliage can be born singly or in clusters along the stem.
The needles may be relatively flat (two sided) or angular in cross section.
Twig Morphology
During autumn and winter, tree identification is based on bud, stem, and bark characteris-
tics. Buds and stems are the principal means of identification.
The shape, size, color, and texture of buds offer interesting identification characteristics.
Leaf scars often provide distinguishing features. The shape of leaf scars and the vascular bundle
arrangement are often used to identify plants.
Lenticels, lip-shaped structures composed of corky cells, are produced through the action of
the cork cambium. They are beneficial for identification because of their different colors and
sizes.
Bud scales, by their size, color, shape, or markings, offer good characteristics for identifica-
tion. The terminal bud scale scar is the place where the previous year’s bud scales were
attached. As the buds open and expand in spring, the scales abscise and leave a distinct scar
around the stem. This scar can be useful for gauging the linear growth in a particular season or
over a number of seasons.
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ParallelVenation
PinnateVenation
PalmateVenation
FIGURE 3. Vein patterns in various leaves.
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Pith is a very valuable plant tissue for differentiating closely related plants. Pith is derived
from a primary meristem. The color and texture of pith can often be used for separating simi-
lar plant types.
Bark
On deciduous trees, bark is the most important
identification feature in the dormant winter period.
Bark varies in thickness, roughness, type of fissures,
and color. Each year the cambium lays down an
annual ring of new cork cells (bark), forcing the old
bark outward. Since the outer bark cannot stretch, it
fissures or cracks into plates, ridges, and scales, form-
ing the bark characteristic of each species.
Flowers
Flowers are important components of positive tree
identification. The flowering periods of most woody
plants average 7 to 14 days. There are numerous vari-
ations in flower shape, but the reproductive parts—
stamens and pistils—are essentially similar.
A flower that has all the parts (sepals, petals, sta-
mens, and one or more pistils) is called complete.
Incomplete flowers lack one or more whorls of floral
parts. Imperfect flowers lack either stamens or pistils.
Perfect flowers have both stamens and pistils.
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FIGURE 4. Each species of tree has its own pattern
of bark.
Petal
Anther
Filament
Stamen
Sepal
Pedicel
ReceptacleOvary
Pistil
Stigma
Style
FIGURE 5. Diagram of a perfect flower.
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Trees may be monecious or dioecious. Monoecious means that staminate and pistillate
flowers are present on the same plant but in different structures. Dioecious means the stami-
nate and pistillate flowers are borne on different plants.
Some trees have solitary flowers, and others have flowers borne on structures called inflo-
rescences. An inflorescence is a collection of individual flowers arranged in some specific
fashion.
Fruit
Fruit offers positive identification features. The longitudinal section of the typical flower
presents a representative view of the ovary. The ovary is the forerunner of the fruit and is
defined as an unripened fruit. The ovary is composed of one or more carpels. A carpel is a
highly modified leaf-like structure that encloses ovules (forerunners of seeds).
A simple fruit consists of a single enlarged ovary composed of one carpel. Simple fruits can
be divided into two major groups: dry and fleshy. Dry fruits can be divided into indehiscent
and dehiscent.
Indehiscent fruits are fruits that do not split open at maturity. There are several types,
including achene, samara, and nut. An achene is a one-seeded fruit with the seed attached at
only one place to the pericarp. The pericarp is very close fitting and does not split open, at least
along regular established lines. A samara is usually one seeded, with a membranous wing that
develops from the pericarp. A nut is a bony, hard, one-seeded fruit. The pericarp is bony
throughout.
Dehiscent fruits split open when mature. There are several types, including legume, fol-
licle, and capsule. A legume (pod) is composed on one carpel and opens along two sutures. A
follicle is composed of one carpel but splits open at maturity along one suture, exposing several
seeds. A capsule is a many-seeded fruit formed from more than one carpel. The carpels are
united.
Several types of fleshy fruits are common with forest trees, including berry, drupe, and
pome. When the entire pericarp is fleshy, the fruit is called a berry. With a drupe, the pericarp
is clearly differentiated into three layers: the exocarp, the mesocarp, and the endocarp. With a
pome, the pericarp is surrounded by the floral tube, which becomes fleshy and tasty.
Two types of compound fruit are aggregate fruit and multiple fruit. An aggregate fruit con-
sists of two or more carpels. It develops from a single flower that contains many pistils. Several
fruitlets are massed on one receptacle. A multiple fruit consists of several flowers that are more
or less united into one mass.
MAJOR FOREST TREE SPECIES
There are many forest tree species with economic importance.
The term southern pine is applied in the lumber trade to shortleaf pine, loblolly pine, slash
pine, and longleaf pine. The term yellow pine, derived from the yellowish color of the wood, is
equally common for these species. Southern pine lumber has a variety of uses. These include
heavy structural and light framing, interior finish, flooring, sheathing, crates, boxes, railcars,
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and many other industrial uses. Southern pine wood readily takes preservative treatment.
When treated, it is used extensively for poles, piling, fence posts, crossties, foundation timbers,
and other construction materials.
Ash is slightly lighter in color than oak, straight grained, and similar in appearance to plain-
sawn oak, with the exception of having no visible medullary rays. Ash wood possesses high-
strength properties. Ash wood is used to make baseball bats, polo and hockey sticks, play-
ground equipment, skis, tennis rackets, handles for shovels and rakes, trim, doors, and other
woodwork. Ash wood has extensive use in bent wood parts, as it responds to steam bending.
American beech is known for its slow growth. The beech wood is hard, dense, and light in
color. It has a diffuse-porous structure and numerous medullary rays. Flooring is the most
important product made from beech. Products of the furniture and brush industries, truck
body parts, toys, woodenware, and novelties are other uses for beech.
Cottonwood is a rapid-growing tree. The
wood of cottonwood is soft textured and light-
weight. It has especially long fiber that makes it
strong and tough in proportion to its weight.
Principal uses of cottonwood include shipping
containers, paper production, furniture, agri-
cultural implements, and veneer.
Baldcypress is a deciduous conifer, and its
wood is soft. Baldcypress does not warp or
check and may be depended on to stay in place.
It holds paint well. Principal uses of
baldcypress include interior and exterior trim,
paneling, sash, doors, and fencing.
Elms are divided into two groups, soft elm
and hard elm. Elm is difficult to split. Soft elm
is an excellent bending wood and is used exten-
sively for boats and bent parts. Furniture and
truck body parts are some other uses.
Sweetgum is the most important southern
hardwood. Many industries use the sapwood of
sweetgum for all their needs. The sapwood of
sweetgum is used in furniture, cabinets, con-
tainers, and general millwork.
Black tupelo grows slowly and has a uniform appearance, indistinct annual rings, and an
interlocking grain. It is a tough wood that is difficult to split.
Hackberry wood is creamy white, ring-porous, and uniform in texture. It has a high resis-
tance to warping and shrinkage. The wood is used extensively in the furniture industry and in
the making of veneer.
No wood compares to hickory for strength, toughness, and elasticity. Hickory is used to
make tool handles, skis, veneer, and rungs on ladders.
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FIGURE 6. Among the uses for wood from cottonwood trees
are shipping containers, furniture, and agricultural
implements.
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The wood of pecan hickories has a pleasing grain pattern and is not as hard as the wood of
true hickories. Pecan wood is used to make furniture, flooring, decking in railroad cars, trailer
parts, and expensive cabinets.
The wood of magnolia is soft, fine textured, and straight grained. The wood is excellent for
interior trim, paneling, furniture, veneer, and doors.
Soft maple is used for furniture, paneling, toys, shipping containers, and specialty kitchen
cabinets.
No hardwood is more widely known or used than
oak. Two groups of oak are the white oak group and
red oak group. Oak is a universal wood, used for
many purposes. Oak wood is well adapted to any fin-
ishing treatment. Its strength is ideal for structural
use. It is unequaled for flooring and makes the best
railroad ties. White oak is used for barrels and casts
for liquids. Other uses for oak include decking for
railroad cars, furniture, millwork, and novelties.
The wood of the sycamore is fairly hard, stiff, and
strong. Sycamore is used in furniture and furniture
parts, millwork, and novelties.
Yellow poplar is known for its ability to resist
warping and to take a smooth, lasting paint or enamel
finish. Yellow poplar is used in furniture, as core
stock in veneer, and for wood boxes, exterior trim,
piano parts, fixtures, toys, and novelties.
Black willow is one of the lightest and softest
woods in North America, yet it is a strong wood.
Black willow uses include paneling, furniture, cas-
kets, shipping containers, interior trim, veneer, and
toys.
Honeylocust wood is used in the manufacture of furniture, pallets, and skis.
Sassafras wood is a very durable, hard-textured wood used in manufacturing furniture. It is
also used in boat construction, oars, exterior trim, and general millwork.
Eastern redcedar is most commonly used in the making of cedar chests and in the lining of
closets.
Atlantic white cedar is used for boat planks, tank stock, shingles, millwork, and lumber for
crating.
Red mulberry is used in the manufacture of caskets.
At one time, red bay was in demand for use in shipbuilding.
Black walnut is used in quality furniture, gunstocks, caskets, and specialty items.
American holly is used for making piano keys, cabinets, veneer, and fancy inlays.
Southern catalpa is used to make fence posts.
Black cheery is used in quality furniture, interior trim, paneling, and cabinet making.
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FIGURE 7. Oak trees produce the most common
hardwood.
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Persimmon wood is hard and strong and is in demand for golf club heads and weaving
loom shuttle blocks.
Basswood does not significantly warp and is used for molding, Venetian blinds, core stock
for veneer paneling, excelsior, food containers, pulpwood fruit containers, and tongue
depressors.
Douglas-fir is the most important commercial tree species in the United States. The wood
is primarily used for dimensional lumber and plywood veneer.
Red alder wood is lightweight and has low shrinkage. It is used for furniture, doors, sash,
panel stock, and millwork.
Aspen wood is straight grained and easily worked. It is used for lumber, pulpwood, veneer,
excelsior, matches, pallets, boxes, crating, and particleboard.
Paper birch is used for turned products, while yellow and sweet birch are primarily used for
furniture, crates, barrels and casks, interior finish, baskets, and woodenware.
Alaska cedar is used for furniture, small boats, and novelties.
Balsam fir wood is lightweight and is mainly used for pulpwood.
Western fir wood is lightweight but strong. It is primarily used for lumber and general mill-
work.
Eastern hemlock is coarse, lightweight, and low in strength. It is primarily used for lumber
and pulpwood and in the manufacture of boxes and crates.
Western hemlock is a lightweight wood of moderate strength. The wood is principally used
for pulpwood, lumber, plywood, and the manufacture of boxes, crates, flooring, and pallets.
Incense cedar wood is lightweight, is moderately low in strength, and has a spicy odor. The
wood is used principally for lumber and fence posts.
Eastern white pine wood is lightweight and mod-
erately soft. It is mainly used for lumber.
Ponderosa pine wood is used mainly for lumber
and to a lesser extent for poles, posts, veneer, ties, and
piles.
Sugar pine wood is easy to work and is used
almost entirely for lumber products.
Western white pine wood is lightweight and mod-
erately low in strength. It is used for lumber and in
building construction.
Redwood, or sequoia wood, is easy to work and is
resistant to decay. The wood is used for building,
cooling towers, tanks, house siding, shingles, and hot
tubs.
Eastern spruce wood is moderately lightweight
and easily worked. It is primarily used for pulpwood.
Sitka spruce wood is a desirable wood for musical
instruments because of its resonance qualities. The
wood is also used for lumber, pulpwood, cooperage,
furniture, millwork, and boats.
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FIGURE 8. Ponderosa pine trees.
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Summary:
� Coniferous tree species are called gymnosperms. Broad-leaved species are calledangiosperms.
Hardiness is a plant’s ability to withstand cold temperatures.
The leaf, bud, stem, flower, and fruit of a tree are useful in identifying the species.Most trees can be identified by the type, size, shape, color, texture, and arrangementof leaves. Angiosperms have broad leaves, while gymnosperms have needle-likeleaves. During autumn and winter, tree identification is based on stem, bud andbark characteristics. Some trees have solitary flowers, and others have flowers borneon structures called inflorescences. Simple fruits can be divided into two majorgroups: dry and fleshy. Dry fruit types include achene, samara, nut, legume, follicle,and capsule. Types of fleshy fruits are berry, drupe, and pome. Two types of com-pound fruit are aggregate fruit and multiple fruit.
There are numerous tree species with economic importance.
Checking Your Knowledge:
� 1. How do gymnosperms and angiosperms differ?
2. What is hardiness?
3. What are the different types of leaf structures and shapes?
4. What features of a leaf, bud, stem, flower, and fruit are used in plant identifi-cation?
5. What are some economically important tree species?
Expanding Your Knowledge:
� Identify tree species in your area using a key or knowledge of leaf, bud, stem,flower, and fruit morphology.
Web Links:
� 680 Tree Fact Sheets
http://hort.ufl.edu/trees/
United States Forest Service Tree List
http://www.fs.fed.us/database/feis/plants/tree/
Arborday.org Tree Guide
http://www.arborday.org/treeguide/
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