98 General Care of Trees 
and the more they lie in the length direction of the stem, 
the more readily are they covered; ze., the more live cam- 
bium borders them sideways, the more active the foliage 
above the wound, and the more directly the repairing cam- 
bium is fed. 
The severity with which a tree may be pruned depends, 
then, mainly on its capacity to cover the wounds in a reason- 
able time, and since this is a result of food elaboration, it 
depends on the growth conditions of the tree. Therefore, 
the tree surgeon, like the surgeon in the hospital, must 
consider the condition of the patient. The pruning may 
be executed in the most careful and approved manner, and 
yet the result may be disastrous if the vitality of the tree is 
not equal to the task of repair. If the pruning were accom- 
panied by attention to the vigor of the tree in improving its 
chances for nutrition, results would more often be satis- 
factory. Hence, if you prune heavily, do what you would 
expect to do with a human being that has an operation to 
undergo; make it comfortable and keep it well fed in order 
to invigorate its constitution. 
Specific Rules. Pruning of ornamental and shade trees 
is practised, then, 
(1) to remove superfluous and injurious parts, 
(2) to keep the trees within manageable shape and limits, 
(3) to train the tree to desirable form, 
(4) to modify the vigor of the tree. 
Pruning for Balance. The first pruning is to be done at 
the time of planting, when it is needful to restore the balance 
between the branch system and the root system, the latter 
often having been curtailed in the operation of transplanting 
the tree. First, all injured roots need attention. Broken 
ones must be cut with a sharp, smooth draw cut, in such a 
manner that the face is on the lower side, so that from it 
