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[Illustration: Frontispiece.
"Come forth into the light of things,
Let Nature be your Teacher."
--WORDSWORTH.]
STUDIES OF TREES
BY
J.J. LEVISON, M.F.
Lecturer on Ornamental and Shade Trees, Yale University Forest School;
Forester to the Department of Parks, Brooklyn, N.Y.
FIRST EDITION
FIRST THOUSAND
1914
PREFACE
In presenting this volume, the author is aware that there are several
excellent books, dealing with one phase or another of tree life, already
before the public. It is believed, however, that there is still need for
an all-round book, adapted to the beginner, which gives in a brief and
not too technical way the most important facts concerning the
identification, structure and uses of our more common trees, and which
considers their habits, enemies and care both when growing alone and
when growing in groups or forests.
In the chapters on the identification of trees, the aim has been to
bring before the student only such characters and facts as shall help
him to distinguish the tree readily during all seasons of the year.
Special stress is laid in each case on the most striking peculiarities.
Possible confusion with other trees of similar appearance is prevented
as far as possible through comparisons with trees of like form or habit.
Only such information is given concerning the structure and requirements
of trees as will enable the reader better to understand the subsequent
chapters. In the second half of the book, practical application is made
of the student's general knowledge thus acquired, and he is acquainted
with the fundamental principles of planting, care, forestry, wood
identification and nature study.
The author recognizes the vastness of the field he is attempting to
cover and the impossibility of even touching, in a small hand-book of
this character, on every phase of tree study. He presumes no further;
yet he hopes that by adhering to what is salient and by eliminating the
less important, though possibly interesting, facts, he is able to offer
a general and elementary _résumé_ of the whole subject of value to
students, private owners, farmers and teachers.
In the preparation of Chapter VIII on "Our Common Woods: Their
Identification, Properties and Uses," considerable aid has been received
from Prof. Samuel J. Record, author of "Economic Woods of the United
States." Acknowledgment is also due to the U.S. Forest Service for the
photographs used in Figs. 18, 122 to 138 inclusive and 142; to Dr.
George B. Sudworth, Dendrologist of the U.S. Forest Service, for
checking up the nomenclature in the lists of trees under Chapter V; to
Dr. E.P. Felt, Entomologist of the State of New York, for suggestions in
the preparation of the section of the book relating to insects; to Dr.
W.A. Murrill, Assistant Director of the New York Botanical Gardens, for
Fig. 108; and to Mr. Hermann W. Merkel, Chief Forester of the New York
Zoological Park, for Figs. 26, 59 and 60.
J.J. LEVISON.
BROOKLYN, N.Y.
June, 1914.
CONTENTS
CHAPTER I
HOW TO IDENTIFY TREES
The Pines
The Spruce and Hemlock
The Red Cedar and Arbor-vitae
CHAPTER II
HOW TO IDENTIFY TREES (Continued)
The Larch and Cypress
The Horsechestnut, Ash, and Maple
Trees Told by their Form
Trees Told by their Bark or Trunk
The Oaks and Chestnut
CHAPTER III
HOW TO IDENTIFY TREES (Continued)
The Hickories, Walnut, and Butternut
Tulip Tree, Sweet Gum, Linden, Magnolia, Locust, Catalpa, Dogwood,
Mulberry, and Osage Orange
CHAPTER IV
THE STRUCTURE AND REQUIREMENTS OF TREES
CHAPTER V
WHAT TREES TO PLANT AND HOW
Trees for the Lawn
Trees for the Street
Trees for Woodland
Trees for Screening
CHAPTER VI
THE CARE OF TREES
Insects Injurious to Trees and How to Combat Them
Important Insects
Tree Diseases
Pruning Trees
Tree Repair
CHAPTER VII
FORESTRY
What Forestry Is and What It Does
Care of the Woodland
CHAPTER VIII
OUR COMMON WOODS: THEIR IDENTIFICATION, PROPERTIES AND USES
Woods Without Pores (Soft woods)
Woods with Pores (Hard woods)
CHAPTER IX
AN OUTDOOR LESSON ON TREES
INTRODUCTION
A good many popular books on trees have been published in the United
States in recent years. The continually increasing demand for books of
this character indicates the growing public interest not only in the
trees that we pass in our daily walks, but also in the forest considered
as a community of trees, because of its aesthetic and protective value
and its usefulness as a source of important economic products.
As a nation, we are thinking more about trees and woods than we were
wont to do in the years gone by. We are growing to love the trees and
forests as we turn more and more to outdoor life for recreation and
sport. In our ramblings along shady streets, through grassy parks, over
wooded valleys, and in mountain wildernesses we find that much more than
formerly we are asking ourselves what are these trees, what are the
leaf, flower, twig, wood and habit characteristics which distinguish
them from other trees; how large do they grow; under what conditions of
soil and climate do they thrive best; what are their enemies and how can
they be overcome; what is their value for wood and other useful
products; what is their protective value; are they useful for planting
along streets and in parks and in regenerating forests; how can the
trees of our streets and lawns be preserved and repaired as they begin
to fail from old age or other causes? All these questions and many more
relating to the important native and exotic trees commonly found in the
states east of the Great Lakes and north of Maryland Mr. Levison has
briefly answered in this book. The author's training as a forester and
his experience as a professional arboriculturist has peculiarly fitted
him to speak in an authoritative and interesting way about trees and
woods.
The value of this book is not in new knowledge, but in the simple
statement of the most important facts relating to some of our common
trees, individually and collectively considered. A knowledge of trees
and forests adds vastly to the pleasures of outdoor life. The more we
study trees and the more intimate our knowledge of the forest as a unit
of vegetation in which each tree, each flower, each animal and insect
has its part to play in the complete structure, the greater will be our
admiration of the wonderful beauty and variety exhibited in the trees
and woods about us.
J.W. TOUMEY,
Director, Yale University Forest School.
NEW HAVEN, CONN.,
June, 1914.
STUDIES OF TREES
CHAPTER I
HOW TO IDENTIFY TREES
There are many ways in which the problem of identifying trees may be
approached. The majority attempt to recognize trees by their leaf
characters. Leaf characters, however, do not differentiate the trees
during the other half of the year when they are bare. In this chapter
the characterizations are based, as far as possible, on peculiarities
that are evident all year round. In almost every tree there is some one
trait that marks its individuality and separates it, at a glance, from
all other trees. It may be the general form of the tree, its mode of
branching, bark, bud or fruit. It may be some variation in color, or, in
case of the evergreen trees, it may be the number and position of the
needles or leaves. The species included in the following pages have thus
been arranged in groups based on these permanent characters. The
individual species are further described by a distinguishing paragraph
in which the main character of the tree is emphasized in heavy type.
The last paragraph under each species is also important because it
classifies all related species and distinguishes those that are liable
to be confused with the particular tree under consideration.
GROUP I. THE PINES
[Illustration: FIG. 1.--Twig of the Austrian Pine.]
How to tell them from other trees: The pines belong to the _coniferous_
class of trees; that is, trees which bear cones. The pines may be
told from the other coniferous trees by their leaves, which are in
the form of _needles_ two inches or more in length. These needles
keep green throughout the entire year. This is characteristic of all
coniferous trees, except the larch and cypress, which shed their
leaves in winter.
[Illustration: FIG. 2.--Twig of the White Pine.]
The pines are widely distributed throughout the Northern Hemisphere,
and include about 80 distinct species with over 600 varieties. The
species enumerated here are especially common in the eastern part of
the United states, growing either native in the forest or under
cultivation in the parks. The pines form a very important class of
timber trees, and produce beautiful effects when planted in groups
in the parks.
How to tell them from each other: The pine needles are arranged in
_clusters_; see Fig. 1. Each species has a certain characteristic
number of needles to the cluster and this fact generally provides
the simplest and most direct way of distinguishing the different
pines.
In the white pine there are _five_ needles to each cluster, in the
pitch pine _three_, and in the Scotch pine _two_. The Austrian pine
also has two needles to the cluster, but the difference in size and
character of the needles will distinguish this species from the
Scotch pine.
THE WHITE PINE (_Pinus strobus_)
Distinguishing characters: The tree can be told at close range by the
number of needles to each cluster, Fig. 2. There are *five* needles
to each cluster of the white pine. They are bluish green, slender,
and about four inches in length.
At a distance the tree may be told by the *right angles* which the
branches form with the main trunk, Fig. 3. No other pine shows this
character.
Form and size: A tall tree, the stateliest of the evergreens.
Range: Eastern North America.
Soil and location: Prefers a deep, sandy soil, but will grow in almost
any soil.
Enemies: Sucking insects forming white downy patches on the bark and
twigs, the _white pine weevil_, a boring insect, and the _white pine
blister rust_, a fungus, are among its principal enemies.
[Illustration: FIG. 3.--The White Pine.]
Value for planting: Aside from its value as an ornamental tree, the
white pine is an excellent tree to plant on abandoned farms and for
woodlands and windbreaks throughout the New England States, New
York, Pennsylvania, and the Lake States.
Commercial value: The wood is easily worked, light, durable, and will
not warp. It is used for naval construction, lumber, shingles,
laths, interior finish, wooden ware, etc.
Other characters: The _fruit_ is a cone, four to six inches long.
Comparisons: The tree is apt to be confused with the _Bhotan pine_
(_Pinus excelsa_), which is commonly grown as an ornamental tree.
The Bhotan pine, however, has needles much longer and more drooping
in appearance.
THE PITCH PINE (_Pinus rigida_)
Distinguishing characters: Here there are *three* needles to each
cluster, Fig. 4. They are dark, yellowish-green needles about four
inches long. The rough-looking _branches_ of the tree may be seen
_studded with cones_ throughout the year, and _clusters of leaves_
may be seen _sprouting directly from the trunk_ of the tree; see
Fig. 5. The last two are very characteristic and will distinguish
the tree at a glance.
Form and size: It is a low tree of uncertain habit and extremely rough
looking at every stage of its life. It is constantly full of dead
branches and old cones which persist on the tree throughout the
year.
Range: Eastern United States.
Soil and location: Grows in the poorest and sandiest soils where few
other trees will grow. In New Jersey and on Long Island where it is
native, it proves so hardy and persistent that it often forms pure
stands excluding other trees.
[Illustration: FIG. 4.--Twig of the Pitch Pine.]
Enemies: None of importance.
Value for planting: Well adapted for the sea coast and other exposed
places. It is of extremely uncertain habit and is subject to the
loss of the lower limbs. It frequently presents a certain
picturesqueness of outline, but it could not be used as a specimen
tree on the lawn.
[Illustration: FIG. 5.--The Pitch Pine.]
Commercial value: The wood is coarse grained and is used for rough
lumber, fuel, and charcoal.
Other characters: The _fruit_ is a cone one to three
inches long, persistent on the tree for several years.
THE SCOTCH PINE (_Pinus sylvestris_)
Distinguishing characters: There are *two* needles to each cluster, and
these are _short_ compared with those of the white pine, and
_slightly twisted_; see Fig. 6. The _bark_, especially along the
upper portion of the trunk, _is reddish_ in color.
Form and size: A medium-sized tree with a short crown.
Range: Europe, Asia, and eastern United States.
Soil and location: Will do best on a deep, rich, sandy soil, but will
also grow on a dry, porous soil.
Enemies: In Europe the Scotch pine has several insect enemies, but in
America it appears to be free from injury.
Value for planting: Suitable for windbreaks and woodland planting. Many
excellent specimens may also be found in our parks.
Commercial value: In the United States, the wood is chiefly used for
fuel, though slightly used for barrels, boxes, and carpentry. In
Europe, the Scotch pine is an important timber tree.
Comparisons: The Scotch pine is apt to be confused with the _Austrian
pine_ (_Pinus austriaca_), because they both have two needles to
each cluster. The needles of the Austrian pine, however, are much
longer, coarser, straighter, and darker than those of the Scotch
pine; Fig. 1. The form of the Austrian pine, too, is more
symmetrical and compact.
[Illustration: FIG. 6.--Twig of the Scotch Pine.]
The _red pine_ (_Pinus resinosa_) is another tree that has two
needles to each cluster, but these are much longer than those of the
Scotch pine (five to six inches) and are straighter. The bark, which
is reddish in color, also differentiates the red pine from the
Austrian pine. The position of the cones on the red pine, which
point outward and downward at maturity, will also help to
distinguish this tree from the Scotch and the Austrian varieties.
GROUP II. THE SPRUCE AND HEMLOCK
How to tell them from other trees: The spruce and hemlock belong to the
evergreen class and may be told from the other trees by their
_leaves_. The characteristic leaves of the spruce are shown in Fig.
9; those of the hemlock in Fig. 10. These are much shorter than the
needles of the pines but are longer than the leaves of the red cedar
or arbor vitae. They are neither arranged in clusters like those of
the larch, nor in feathery layers like those of the cypress. They
adhere to the tree throughout the year, while the leaves of the
larch and cypress shed in the fall.
The spruces are pyramidal-shaped trees, with tall and tapering
trunks, thickly covered with branches, forming a compact crown. They
are widely distributed throughout the cold and temperate regions of
the northern hemisphere, where they often form thick forests over
extended areas.
There are eighteen recognized species of spruce. The Norway spruce
has been chosen as a type for this group because it is so commonly
planted in the northeastern part of the United States.
The hemlock is represented by seven species, confined to temperate
North America, Japan, and Central and Western China.
[Illustration: FIG. 7.--The Norway Spruce.]
How to tell them from each other: The needles and branches of the spruce
are _coarse_; those of the hemlock are _flat and graceful_. The
individual leaves of the spruce, Fig. 9, are four-sided and green or
blue on the under side, while those of the hemlock, Fig. 10, are
flat and are _marked by two white lines_ on the under side.
THE NORWAY SPRUCE (_Picea excelsa_)
Distinguishing characters: The characteristic appearance of the
full-grown tree is due to the *drooping branchlets* carried on *main
branches which bend upward* (Fig. 7).
Leaf: The leaves are dark green in color and are _arranged spirally_,
thus making the twigs coarser to the touch than the twigs of the
hemlock or fir. In cross-section, the individual leaflet is
quadrilateral, while that of the pine is triangular.
Form and size: A large tree with a straight, undivided trunk and a
well-shaped, conical crown (Fig. 7).
Range: Northern Europe, Asia, northern North America.
Soil and location: Grows in cool, moist situations.
Enemies: The foliage of the spruce is sometimes affected by _red
spider_, but is apt to be more seriously injured by drought, wind,
and late frosts.
Value for planting: Commonly planted as an ornamental tree and for
hedges. It does well for this purpose in a cool northern climate,
but in the vicinity of New York City and further south it does not
do as well, losing its lower branches at an early age, and becoming
generally scraggly in appearance.
[Illustration: FIG. 8.--A Group of Hemlock.]
Commercial value: The wood is light and soft and is used for
construction timber, paper pulp, and fuel.
Other characters: The _fruit_ is a large slender cone, four to seven
inches long.
Comparisons: The _white spruce_ (_Picea canadensis_) may be told from
the Norway spruce by the whitish color on the under side of its
leaves and the unpleasant, pungent odor emitted from the needles
when bruised. The cones of the white spruce, about two inches long,
are shorter than these of the Norway spruce, but are longer than
those of the black spruce.
It is essentially a northern tree growing in all sorts of locations
along the streams and on rocky mountain slopes as far north as the
Arctic Sea and Alaska. It often appears as an ornamental tree as far
south as New York and Pennsylvania.
The _black spruce_ (_Picea mariana_) may be told from the other
spruces by its small cone, which is usually only about one inch in
length. In New England it seldom grows to as large a size as the
other spruce trees.
It covers large areas in various parts of northern North America and
grows to its largest size in Manitoba. The black spruce has little
value as an ornamental tree.
The _Colorado blue spruce_ (_Picea parryana_ or _Picea pungens_)
which is commonly used as an ornamental tree on lawns and in parks,
can be told from the other spruces by its pale-blue or sage-green
color and its sharp-pointed, coarse-feeling twigs. Its small size
and sharp-pointed conical form are also characteristic.
It grows to a large size in Colorado and the Middle West. In the
Eastern States and in northern Europe where it is planted as an
ornamental tree, it is usually much smaller.
[Illustration: FIG. 9.--Twig of the Norway Spruce.]
HEMLOCK (_Tsuga canadensis_)
Distinguishing characters: Its leaves are arranged in *flat layers*,
giving a flat, horizontal and graceful appearance to the whole
branch (Fig. 8). The individual leaves are dark green above, lighter
colored below, and are *marked by two white lines on the under side*
(Fig. 10).
The leaves are arranged on little stalks, a characteristic that does
not appear in the other evergreen trees.
Form and size: A large tree with a broad-based pyramidal head, and a
trunk conspicuously tapering toward the apex. The branches extend
almost to the ground.
Range: The hemlock is a northern tree, growing in Canada and the United
States.
Soil and location: Grows on all sorts of soils, in the deepest woods as
well as on high mountain slopes.
Enemies: None of importance.
Value for planting: The hemlock makes an excellent hedge because it
retains its lowest branches and will stand shearing. In this respect
it is preferable to the spruce. It makes a fair tree for the lawn
and is especially desirable for underplanting in woodlands, where
the shade from the surrounding trees is heavy. In this respect it is
like the beech.
Commercial value: The wood is soft, brittle, and coarse-grained, and is
therefore used mainly for coarse lumber. Its bark is so rich in
tannin that it forms one of the chief commercial products of the
tree.
Other characters: The _fruit_ is a small cone about ¾ of an inch long,
which generally hangs on the tree all winter.
[Illustration: FIG. 10.--Twig of the Hemlock.]
GROUP III. THE RED CEDAR AND ARBOR-VITAE
How to tell them from other trees: The red cedar (juniper) and
arbor-vitae may be told from other trees by their _leaves_, which
remain on the tree and keep green throughout the entire year. These
leaves differ from those of the other evergreens in being much
shorter and of a distinctive shape as shown in Figs. 12 and 13. The
trees themselves are much smaller than the other evergreens
enumerated in this book. Altogether, there are thirty-five species
of juniper recognized and four of arbor-vitae. The junipers are
widely distributed over the northern hemisphere, from the Arctic
region down to Mexico in the New World, and in northern Africa,
China, and Japan in the Old World. The arbor-vitae is found in
northeastern and northwestern America, China, and Japan. The species
mentioned here are those commonly found in America.
How to tell them from each other: The _twigs_ of the arbor-vitae are
_flat and fan-like_ as in Fig. 13; the twigs of the red cedar are
_needle-shaped or scale-like_ as in Fig. 12. The foliage of the
arbor-vitae is of a lighter color than that of the red cedar, which
is sombre green. The arbor-vitae will generally be found growing in
moist locations, while the red cedar will grow in dry places as
well. The arbor-vitae generally retains its lower branches in open
places, while the branches of the red cedar start at some distance
from the ground.
RED CEDAR (_Juniperus virginiana_)
[Illustration: FIG. 11.--The Red Cedar.]
Distinguishing characters: The tree can best be told at a glance by its
general form, size and leaves. It is a medium-sized tree with a
_symmetrical, cone-like form_, Fig. 11, which, however, broadens
out somewhat when the tree grows old. Its color throughout the year
is dull green with a tinge of brownish red, and its bark peels in
thin strips.
[Illustration:
FIG. 12(a).--Twig of Young Cedar.
FIG. 12(b).--Twig of Cedar (Older Tree).]
Leaf: In young trees the leaf is needle-shaped, pointed, and marked by a
white line on its under side, Fig. 12(a). In older trees it is
scale-like, Fig. 12(b), and the white line on its under side is
indistinct.
Range: Widely distributed over nearly all of eastern and central North
America.
Soil and location: Grows on poor, gravelly soils as well as in rich
bottom lands.
Enemies: The "_cedar apple_," commonly found on this tree, represents a
stage of the apple rust, and for that reason it is not desirable to
plant such trees near orchards. Its wood is also sometimes attacked
by small _boring insects_.
Value for planting: Its characteristic slender form gives the red cedar
an important place as an ornamental tree, but its chief value lies
in its commercial use.
Commercial value: The wood is durable, light, smooth and fragrant, and
is therefore used for making lead-pencils, cabinets, boxes,
moth-proof chests, shingles, posts, and telegraph poles.
Other characters: The _fruit_ is small, round and berry-like, about the
size of a pea, of dark blue color, and carries from one to four bony
seeds.
Other common names: The red cedar is also often called _juniper_ and
_red juniper_.
Comparisons: The red cedar is apt to be confused with the _low juniper_
(_Juniperus communis_) which grows in open fields all over the
world. The latter, however, is generally of a low form with a flat
top. Its leaves are pointed and prickly, never scale-like, and they
are whitish above and green below. Its bark shreds and its fruit is
a small round berry of agreeable aromatic odor.
ARBOR-VITAE; NORTHERN WHITE CEDAR (_Thuja occidentalis_)
Distinguishing characters: The *branchlets* are extremely *flat and
fan-like*, Fig. 13, and have an agreeable _aromatic odor_ when
bruised. The tree is an evergreen with a _narrow conical form_.
[Illustration: FIG. 13.--Twig of the Arbor-vitae.]
Leaf: Leaves of two kinds, one scale-like and flat, the other keeled,
all tightly pressed to the twig (see Fig. 13).
Form and size: A close, conical head with dense foliage near the base.
Usually a small tree, but in some parts of the northeastern States
it grows to medium size with a diameter of two feet.
Range: Northern part of North America.
Soil and location: Inhabits low, swampy lands; in the State of Maine
often forming thick forests.
Enemies: Very seldom affected by insects.
Value for planting: Is hardy in New England, where it is especially used
for hedges. It is also frequently used as a specimen tree on the
lawn.
Commercial value: The wood is durable for posts, ties, and shingles. The
bark contains considerable tannin and the juices from the tree have
a medicinal value.
Other characters: The _fruit_ is a cone about ½ inch long.
Other common names: Arbor-vitae is sometimes called _white cedar_ and
_cedar_.
Comparisons: The arbor-vitae is apt to be confused with the true _white
cedar_ (_Chamaecyparis thyoides_) but the leaves of the latter are
sharp-pointed and not flattened or fan-shaped.