, STREET TREES. 53 
form too dense a head. The interior branches of these should be 
removed and the head made as open as possible while the work can 
be done with a knife. No attempt should be made to alter the 
natural form of a tree but only to insure its best development. A 
skillfully pruned young tree will show no evidences of the pruning 
after three or four years. 
CARE OF MATURE TREES. 
PRUNING. 
It is very little trouble to train a tree into a good shape by using 
the pruning knife while the limbs are small, but it is usually difficult 
to re-form a tree after it has grown to maturity. One who under- 
stands tree growth, however, can often reshape the top of a neglected 
tree to advantage, though many who make a business of tree trim- 
ming know so little about it that they do more harm than good. 
More mature trees have been hurt by severe pruning than have been 
helped. Of course, dead or dying wood should be removed when- 
ever it is found, no matter what the age of the tree. This should 
be done by cutting off the limb back to the nearest healthy crotch. 
A limb should not be cut off square across (fig. 21) unless the tree 
is apparently in a dying condition and the whole top is treated thus 
in an attempt to save its life. In such a case, a second pruning 
should follow within two years, at which time the stubs left at the 
first trimming should be cut off in a proper manner near the newly 
started limbs. Healthy silver maples and willows are frequently 
cut in this way, but the maples in particular would better be cut down 
at once than to subject the public to the dangers of the insidious 
decay that almost always follows such an operation on these trees 
and completes their destruction promptly. 
Trees that have been neglected a long time frequently have inter- 
fering or crossing branches, or are too low headed or too densely 
headed for the place where they are growing. Defects of this kind 
may be at least partially remedied. The removal of limbs by cutting 
them off at a crotch in such a manner that the wound is parallel with 
the remaining branch (fig. 37) inflicts the least possible damage. 
Such a wound in a healthy tree will soon heal over if the cut is made 
through the slight collar or ring that is nearly always present at the 
base of a branch. The closer this cut can be made to the trunk 
the better the appearance when the cut is healed. The closer the 
cut the larger the wound, but the difference is unimportant if the 
wood is well protected until it is healed. These operations are 
entirely different in purpose and result from the ‘‘heading in”’ or 
“heading back”’ so often practiced under the guise of tree pruning, 
either from a false notion of forming a top or for the passage of wires. 
Changing the form of a tree by pruning should not be attempted. 
Each species has its own form or forms, and no attempt should be 
