224 TREES AND TREE-PLANTING. 
be cut off at once, as some, which it is ultimately requisite 
to trim away, may at that particular stage of growth 
be beneficial to the tree of which they are members. 
Again, it may be observed that there are many cases 
of failure from not pruning enough; so between these 
two questions the considerations of the planter must 
take a moderate tendency, in conformity, of course, with 
his own observations, in connection with the natural 
habit of the tree he is to practise on, and the purpose 
for which his exertions are designed. 
The great object of pruning is to obtain a straight 
stem, regular outline of tree, and equalize the members 
necessary to support its thrift. For the first of these 
requirements it is usual to begin training while the tree 
is young, and for this reason the nursery is the place 
best suited to start from, as the limbs of the trees in 
their infancy are smaller and their tendency more easily 
observable then than if left till of greater maturity ; 
besides, the wounds formed by the separation of young 
branches from their parent stem will not be so large as 
to require any serious attention. 
The shade necessary for the protection of the tree- 
stem from the drying influences of the sun makes it nec- 
essary that the lower branches of young trees, especially 
if growing in open ground, be preserved for the pur- 
pose to which they are best suited; generally trees so 
situated require at least two thirds of their height as a 
source of shade to their stems, and for the production of 
that vital property naturally possessed by the leaves so 
indispensable to growth. But when trees are grown col- 
lectively, and for the production of timber, so that in- 
dividually they shade each other, then they can be con- 
veniently pruned to two thirds of their height, allowing 
only the remaining one third as a requisite shade. 
The most suitable time for the pruning of trees is in 
midsummer, when the leaves are in full bloom and the 
sap in a state of quietude. They may also be pruned 
