Albert Francis Blakeslee.

Trees in winter; their study, planting, care and identification online

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or otherwise fastened to mounting paper. It has been the writer's
practice to require of students a small collection of leaves in the
fall and a similar collection of twigs in the winter or early spring.
Accompanying each leaf or twig is given a short characterization
emphasizing its chief marks of distinction. The specimens may be
largely collected on the field trips and the mechanical labor of
preparation is not excessive.

More elaborate individual work can be done by the student if
time is available. Keys can be worked out for various groups
of trees. A tree book may be made including some of the com-
monest forms within a limited area and representing them by spec-
imens, by drawings, by photographs or by half-tone pictures. Such
a tree book may be with or without written matter on each tree
represented, but its preparation would assuredly give one knowl-
edge of the trees studied. In the writer's experience the most ef-
fective way to learn about trees is to write a book on the subJ9ct.

A school collection for permanent exhibition is desirable and
warrants a greater outlay of time and labor than could be given
to the work by the individual students. Each tree should be rep-
sented by at least a leaf, a winter twig, a picture of the bark and
one of the habit. The fruit is also generally desirable. Among
the things that can be added to advantage are the flowers, a seed-
ling, an outline map with shaded areas showing the distribution of
the species, and a series of wood sections such as may be obtained
of R. B. Hough, Lo\wille, N. Y. These specimens of each species
may be mounted together on cotton in shallow, glass-front boxes
such as the Eiker cases, or conveniently exhibited behind glass
which is passepartouted to a firm back in the manner in which pic-


tures are frequently mounted, Ivirkwood in Kature Study
Eeview for January, 1912, describes a method of mounting
specimens in large wooden frames, but if many cases are to be
stored or exhibited the surface dimensions as also the thickness of
the mounts must be kept within limits.

Tree Study in Graded Schools — On account of their con-
spicuousness, accessibility, beauty and utility, trees have formed
an important element in outlines of nature study courses
recommended for elementary schools. Coulter & Patterson in their
Practical Nature Study, to mention but a single book, give valuable
suggestions on tree study with typical lesson plans and topical
outlines by grades and seasons. Farmer's Bulletin No. 468, en-
titled ''Forestry in Nature Study/' may be obtained free by address-
ing The Department of Agriculture, Washington, D. C, and should
be in the hands of every teacher interested in nature work.
This bulletin gives outlines for courses of study for the different
grades and a valuable list of supplementary reading and reference
books for nature study teachers together with a key to the more
common genera of trees based on leaf characters. In view of the
accessibility of this publication and the literature therein cited, it
would be inappropriate to enter into an extended discussion of the
place of tree study in the elementary schools. The present book
would draw attention to the fact that trees in winter are more
available for purposes of study than most have believed. The in-
terest shown by classes of summer school teachers in identifying
specimens of twigs collected the previous winter indicates that the
winter study of trees can be taken up with enthusiasm by teachers
in their schools. In our experience, the winter identification of
trees has proven to students one of the most interesting subjects
of their course. It is of decided value for its training in the power
of accurate observation. The work comes at a time when mate-
rial for natural history study seems scanty and might therefore be
used to bridge over the period between fall and spring which are
unfortunately considered by many the only seasons when study of
outdoor life is possible in the schools.

The markings on a branchlet enable us to read a tree's name.
They may also give us a chapter in the tree's past history as is
shown on page 38. By placing twigs in water in tlie late winter
the bud may be forced and we may learn the future possibilities


that lie bound up in a winter twig. The name of a tree and its
past and future life, however, form but an introduction to the
study of a tree. What are its relations to utility and to human
enjoyment, are questions that should not be neglected. The skill-
ful teacher will be able to correlate tree study with other work and
so direct the natural enthusiasm of children for outdoor observa-
tion that it may not become a burden to the daily program.

An appreciation of natural beauty is a recognized object of nature
study. It must in general, however, remain a valuable by-product
rather than the immediate object of pursuit. An unreasoning ap-
peal to mere wonder and admiration at the beauties of nature is
likely to have an effect opposite to that desired. The appeal must
come in the way of observations and problems and the problems
must be definite. What is the most beautiful single tree, individ-
ual group of trees, the most beautiful street or the most beautiful
home with tree surroundings in the neighborhood? What are the
elements that make them interesting? From what points of view
are they most pleasing, and what is it that gives these viewpoints an
advantage over others? Such questions, modified to suit the
grade of the pupils, have been suggested by Professor Waugh of
Amherst, and the writer can confirm their usability with students.





Before discussing the planting and care of trees, it is well to con-
sider briefly the structure, life and growth of the individual tree
itself. For a fuller treatment of the subject the reader may be re-
ferred to the current text books on botany and forestry.

A tree is a living thing and as such has the same great problems
to meet that face all living organisms — plants as well as animals.
It must have food in order to live and grow and it must provide for
a continuation of its kind. Animals are able to move about in
search for their food which they obtain ready made from other
animals or from plants. The tree, however, like other green
plants is deprived not only of the power of locomotion but also of
the power of using food made by other organisms. It has, there-
fore, to manufacture its own food. This it does by combining
food constituents from the soil with that from the air and is
therefore a manufacturer as well as a consumer of its own products.
In Chapter I, we shall consider the different organs of the tree in
relation to the manufacture of plant food, to growth and to pro-

The Parts of a Tree — There are three main parts to a tree
— roots, leaves and stem. The roots obtain water with dissolved
mineral water from the soil and anchor the tree in place.
The leaves have a double function. They gather carbonic acid
gas from the air and they combine this gaseous food constituent
from the air with the food constituents from the soil in the manu-
facture of plant food. The stem connects the roots with the leaves
and raises the latter to a position favorable for carrying on their
work. The three main parts of a tree may now be considered
more in detail. The diagram in figure 15 may serve to make the
explanations clearer.



carbon dioT^icj^


Fig. 15. Diagram to illustrate parts and functions of a tree. (Modi-
fied after Fernow).



The Root — According to their position, the roots of a tree
may be classified into tap-roots which grow directly down-
ward, surface or tracing roots which occupy a shallow layer just
below ground, and roots which take a position intermediate between
these two types. Some trees like the Hickory, the Bur Oak and
the White Oak regularly develop a strong deep-seated tap-root
and in consequence are able to draw water from the lower levels
but are difficult to transplant; others like the Birches and
Spruces have only surface roots and are therefore dependent
upon the supply of moisture in the shallow upper layers. Most
of our trees, like the Maple and Ash, are found to have a com-
bination of both kinds. Many fonns, moreover, in which one
of these two root types predominates are able to adapt themselves
to the condition of the soil in which they grow. Thus at the
Minnesota Experiment Station, a small Bur Oak growing on dry,
gravelly soil is reported to have developed a tap-root 20 feet long,

Fig. 16. Seedling- of Hornbeam, after Strasburger. r zone of root-
hairs near root-tip; hw, main roots; sw, lateral roots; 1,1, foliage leaves;
e, seed-leaves.


while on moist, fertile clay land in the same section such trees
are believed to have tap-roots seldom more than six feet long.

Absorption of water and minerals in solution is the great service
of roots, but it is only their smallest branchlets — the root fibrils
— that are capable of taking in water. The older parts are soon
covered with a waterproof layer of bark and are of service only in
conducting fluids to the stem and in holding the tree in place. The
fibrils, moreover, do not take in fluids throughout their whole ex-
tent but almost exclusively through fine root-hairs, which in the
shape of minute tabular cells form a velvety covering on their
younger portions (fig. 16). These root-hairs are short-lived, en-
during only for a few days or at most weeks. New hairs, however,
are constanly being formed toward the root tips as those further
back die and shrivel up. In some trees it has been shown that fine
threads of various species of moulds growing in the soil surround
the root fibrils and take the place of root-hairs, but it still remains
true that only the youngest parts of roots are capable of absorbing
water. It can be readily understood, therefore, how serious the
damage may be to the tree when its almost invisible root fibrils are
injured in any way as by transplanting. Fortunately roots can
rapidly regenerate lost parts and, if the need of water is lessened
by judicious pruning of the crown, the new rootlets formed will be
able to absorb enough water to keep the tree from withering.

How far roots extend from the trunk is not easy to observe.
Roots of the Elm have been found clogging up drain pipes 150 feet
from the tree, but such a distance must be exceptional. Garden -
ers claim that the parts underground extend laterally as far as
those above ground and such a condition would bring the young
feeding rootlets directly under the edges of the leafy crown. While
this is far from being strictly true, it should be remembered that the
absorbing fibrils are in a circle at some distance from the trunk. In
consequence, any such treatment of the soil, as adding water or
food constituents, should take place at some distance from the
trunk rather than at its base, in order to benefit the tree.

In order to live and grow, roots must have food. This is made

for them in the leaves and handed down through the stem and

older roots. If the supply of food is diminished by a partial loss

of leaves, some of the roots die. If the suj^ply of water and food

constituents from the soil is lessened by root injuiy a part of the

leafy crown will die. A rather definite balance exists between the

extent of the root system and that of the crown.

ma. r* aa #uu i rrr i iddkom



Fig-. 17. Cross section through a Beech leaf, after Strasburger. ep,
ep", epidermis, the protective covering- of upper and lower surface of
leaf; pi, s and sp, cells containing- little granules of leaf-g-reen or
chlorophyll — the places where plant food is made; st, opening through
the epidermis connecting- the air passages in the leaf with the free air

All parts of plants need oxygen. Eoots obtain it from the air
in the soil. If the roots are too deeply covered, as when the
ground is filled in above them in changing the grade, or if the air
in the soil is driven out by an excess of water, most trees are likely
to suffer. Some forms like the Elm, however, are naturally able to
endure such unfavorable conditions.

The Leaf — It has been already said that trees are like ani-
mals in their general food requirements, but that they have the
added characteristic of being able to make out of elements obtained
from the soil and from the air the complex food which they require.
This manufacture of plant food takes place within the leaf in mi-
nute granules of leaf-green or chlorophyll (fig. 17). Sunlight is
necessary and furnishes the energy for the process. Carbonic acid
gas from the air enters through small openings into the leaf and is
there broken down into oxygen and carbon. The oxygen is re-
turned to the air in the pure state, while the carbon is united with
the water and minerals from the soil. The complex plant food
which is thus built up, is transported to all the growing parts of the
tree and is used in the construction of new leaves, roots and wood.
Carbon is the conspicuous element in wood, comprising one-half of
its dry weight, and in the production of charcoal is left in nearly a
pure state. When wood is comjiletely burned, the process ob-
served in the leaves is reversed. The water passes off as vapor, the
mineral matter is left in the fonn of ashes, while the carbon re-
unites with the oxA'gen of the air in the formation of cabonic acid
gas. The leaf may be compared to a factory. Carl)onic acid gas,
water and dissolved minerals are the raw materials. Plant food


is the finished product. Sunlight is the energy which runs the

The fact that sunlight is necessary for the formation of plant
food in the leaves, explains the poor development of branches that
are partially shaded. The Post Oak, shown on page 101, w^as in-
terfered with by a neighboring tree on the right. The scant growth
of limbs on this side is the result. The lower branches of trees
in the woods die and are ^'^self-pruned" when their leaves are so
shaded that they are no longer able to make sufficient food for a con-
tinuation of growth. It is for this reason, that all forest-grown
trees tend to produce tall trunks with but little branching (fig. 19)
while trees in the open (fig. 18) branch more freely and are there-
fore better able to express the habit characters peculiar to the

Species of trees differ in their ability to tolerate shading. There
are "tolerant" forms like the Hemlock, the Beech and the Sugar
Maple that are able to grow under the shade of other trees, and
"intolerant" forms like the Poplars and Birches that are killed by
a relatively small amount of shading. In planting groups the rela-
tive tolerance of the forms represented should be taken into con-

Although the leaves are arranged in a position favorable to illum-
ination, they are at the same time exposed to conditions favorable
to evaporation. It has been estimated that a Beech 110 years old
"transpired" through its leaves approximately 2,250 gallons of
water during a single summer and that an Oak with some 700,000
leaves transpired about 180 gallons daily. Such a considerable
amount of water lost by the leaves must be made good by the roots
or the tree will perish from thirst. A diminished root absorption,
brought about by injury during transplanting or caused in any
other way, can be neutralized by pruning the crown and thus reduc-
ing the amount of leaf surface exposed to evaporation.
' Trees that drop their leaves all at once are called "diciduous" in
distinction to our Evergreens which retain their foliage through-
out the winter. The latter, however, are not stnctly evergreen.
In the White Pine for example (page 211), leaf scare can be found
in increasing numbers on second and third year's growth and show
that in this species the fall of the foliage is gradual and that its in-
dividual leaves usually do not remain on the tree more than three
years. The evergreen character is generally associated with cone-
bearing forms. The Holly is the only broad-leaved tree of the




northeastern United States that is evergreen, and the Larch is our
only conifer that is deciduous. Some trees, however, like certain
species of Magnolia, are deciduous in New England and evergreen
in the southern states.

The bare-twigged condition prevents the tree from suffering a
more rapid loss of water than its roots could suppply in the winter
season if the broad, thin leaves were left exposed to evaporation. In
the autumn the living substance of the leaf is broken up and with
all the food remaining is withdrawn into the branches. Only the
framework remains and the colors left by the disintegration of the
green chlorophyll. The leaf has served its function as a machine
for the manufacture of plant food and is now ready for the scrap
heap. Before it dies, however, a separating layer forms at the base
of the leaf stalk and heals the wound before the leaf is abstricted.
Cold or dryness may hasten the process, but an early frost may kill
the leaves and prevent their falling in the normal fashion.

Not only the fall of leaves but also their autumn coloring is gen-
erally independent of frost and may at times occur even in mid-
summer. The trees of the northeastern United States show a more
brilliant coloring than those in the more humid climate of Europe,
and even our native species are said to have duller foliage when
grown abroad.

The Stem — The stem of a tree has the function of connect-
ing the roots with the leafy crown and of raising the latter above
the shade of competing forms. A branchlet of the Horse-chestnut
(fig. 20) may be taken as a convenient form to illustrate the vari-
ous markings found on a young stem. The large triangular patches
resembling somewhat closed horse-shoes in shape are the leaf-scars
showing where the bases of the leaf-stalks were attached to the twig
before their fall. The little dots corresponding to the nail holes
in a horse-shoe are the hundle-scars and mark the location of the
so-called fibro-vascular bundles that run through the leaf -stalks and
connect with the veins of the leaf acting thus as the channels for
the transference of raw material and manufactured food to and
from the leaf. The leaf-scars are located at the nodes and the por-
tion between the nodes is called the internode. Scattered
along the twig are little dots, the lenUcels, which are openings that
function to a certain extent like breathing pores.



Terminal Bud ^

Axillary Bud

Fruit Scac

s Node


Leaf Scar ,
Bundle Scar-.— 1

Scale Scars «_
DormBini Bud— d

""v..l year's growth


Fig. 20. Twig of Horse-chestnut.

Above each leaf-scar is normally produced an axillary-hud so
called because located in the axil or angle, made between the twig
and the leaf-stalk when the latter was present. The lateral hud^
are in distinction to the terminal huds at the ends of the twigs.

Buds that produce shoots with leaves are called leaf huds. Cer-
tain of the buds — the floiver huds — do not continue the growth
of the twig but form the flowers which develop into fruit. AVhere
the individual fruit (in the Horse-chestnut the fruit cluster) was



attached, a fruit-scar is left, and these fruit scars furnish evidence
of the amount of fruit produced in previous years.

Each bud contains the rudiments of next year's growth with
shortened internodes and minute leaves folded together like a fan
and packed away within the protective covering of the bud-scales.
Buds begin to form by May or June, but remain during winter in a
condensed condition. Growth in the spring consists, foi the most
part, of a rapid elongation of the internodes and an enlargement
of the parts which are ^already formed in the bud, and may be com-
pleted in a few days. For most trees, the number of leaves and

Fig. 21. Diagram of three-year-old tree after Mueller, to show, on
side B, the number of branches theoretically possible if all the buds
develop and, on side A, the number actually produced. 1 and 2 mark
the end of the first and second year's g-rowth respectively. The branches
have developed from axillary buds such as are seen on the last year's
g'rowth above 2.


flowers a bud is capable of producing is determined not during the
spring elongation of the bud but during its formation the previous
3^ear. At least a single bud is usually formed above each leaf. Of
all the buds produced in a season only a very small number ever
start and grow into branchlets, and the great majority of these
branchlets eventually die and are pruned off by the tree. There
is a struggle for existence among buds and branchlets as well as
among seedlings, and the strongest alone survive. The accompany-
ing diagram (fig. 21) shows the condition that might result from
a free development of buds and branches in contrast with the con-
dition that usually exists. Dormant buds frequently retain their
vitality for many years and may be forced into development if
the growth above them is injured. Adventitious buds are those that
form outside of their regular position at the nodes. They are
responsible for the sprouts that regularly fonn on the cut stump
of Chestnut and many other of our deciduous trees. Poplars and
Willows (p. 351) produce them in abundance when the limbs
are cut back or ^^pollarded."

The bud-scales are modified leaves which protect the parts with-
in from mechanical injury and from loss of moisture, but except
for the prevention of sudden changes of temperature, they are of
little value as a protection against cold as is so often supposed. At
fallirig they leave a ring or band of scale-scars marking the limit
of each yearns growth. These bands often remain distinct for
many 3- ears (see twig of Beech p. 295) and by counting their number
the age of the branchlet may be estimated. Thus it can be readily
seen that the figure of the Horse-chestnut represents growth made
during three years. Each 3'ear a ring of new Avood is formed just
underneath the bark, and a count of the number of these annual
rings between the central pith and the bark, as seen in a cross
section of a branch or trunk, will likewise give the age of the part
investigated. The uppermost buds of a year's growth are gen^
erally the largest and most likely to develop into branches the
following spring. In some species, as many of the Evergreens,
and the Carolina Poplar (p. 261) for example, the branches com-
ing from these more vigorous buds form regular whorls along the
trunk at the upper part of each year's growth and afford for such
species a third means of estimating the age.



By aid of the markings just discussed on the stem the past his-
tory of the tree can be deciphered often for a considerable num-

}—■ - Outer Bark
Inner BarK
- Cambium^

r Summer Wood
■Spring Wood

-Medullary Raij

Med. "Ray

' — Inner Bark "">^''
Sap wood - '
-Outer BarK

^^ Spring Wood

Heart wood

Fig. 22. Diagram to iUustrate structure of a block of Oak wood.


ber of years. The parts of a twig as furnishing a means of iden-
tification is further discussed in Part II.

,A general idea of the internal structure of an older stem may
be obtained by the study of a block of Oak wood (fig. 22). Aside
from the relatively narrow pith in the center, the trunk of a tree is
made up of three general regions : — the protective covering of
harh outside, the thick cylinder of wood within and the thin sheet
of delicate tissue forming the camhium between these two regions.
The cambium layer is of special interest since it is the only part
that remains alive throughout the growth of the trees. In making
a whistle, the boy finds in this layer an easy place of separation
of wood from the bark. Each year its outer surface forms a new
layer of the bark and its inner surface a new layer of wood. By
adding an annual ring of wood the cambium itself is pushed out
by just so much each season away from the center of the tree but
always remains a narrow layer. The bark, as well as the wood, is

Online LibraryAlbert Francis BlakesleeTrees in winter; their study, planting, care and identification → online text (page 3 of 31)