insects and disease into the heart of
    the tree.  But all other pruning, whether it be for the purpose of
    perfecting the form in shade trees, or for increasing the production
    of fruit in orchard trees, should be confined to certain seasons. 
    Shade and ornamental trees can best be pruned in the fall, while the
    leaves are still on the tree and while the tree itself is in
    practically a dormant state.

Proper cutting:  All pruning should be commenced at the top of the tree
    and finished at the bottom.  A shortened branch (excepting in poplars
    and willows, which should be cut in closely) should terminate in
    small twigs which may draw the sap to the freshly cut wound; where a
    branch is removed entirely, the cut should be made-close and even
    with the trunk, as in Fig. 113.  Wherever there is a stub left after
    cutting off a branch, the growing tissue of the tree cannot cover it
    and the stub eventually decays, falls out and leaves a hole (see
    Fig. 114), which serves to carry disease and insects to the heart of
    the tree.  This idea of close cutting cannot be over-emphasized.

Where large branches have to be removed, the splitting and ripping of the bark along the trunk is prevented by making one cut beneath the branch, about a foot or two away from the trunk, and then another above, close to the trunk.

[Illustration:  FIG. 113.—­Branches Properly Cut Close to the Trunk.]

Too severe pruning:  In pruning trees, many people have a tendency to cut
    them back so severely as to remove everything but the bare trunk and
    a few of the main branches.  This process is known as “heading
    back.”  It is a method, however, which should not be resorted to
    except in trees that are very old and failing, and even there only
    with certain species, like the silver maple, sycamore, linden and
    elm.  Trees like the sugar maple will not stand this treatment at
    all.  The willow is a tree that will stand the process very readily
    and the Carolina poplar must be cut back every few years, in order
    to keep its crown from becoming too tall, scraggy and unsafe.

[Illustration:  FIG. 114.—­A Limb Improperly Cut.  Note how the stub is decaying and the resulting cavity is becoming diseased.]

Covering wounds:  The importance of immediately covering all wounds with
    coal tar cannot be overstated.  If the wound is not tarred, the
    exposed wood cracks, as in Fig. 115, providing suitable quarters for
    disease germs that will eventually destroy the body of the tree. 
    Coal tar is by far preferable to paint and other substances for
    covering the wound.  The tar penetrates the exposed wood, producing
    an antiseptic as well as a protective effect.  Paint only forms a
    covering, which may peel off