102 General Care of Trees 
In planted groups of several species, the fact (referred to on 
pages 25 and 73) must be keptin mind that the different species 
vary in regard to the amount of light which they require 
for normal development. Some, such as the Beech, Maple, 
and Holly, are very shade-enduring and at 
the same time they themselves make a dense 
shade; if associated with such light-needing 
species as the Tulip tree, the Ash, Walnut, 
Cherry, and many others, the latter will be 
— at a great disadvantage: the shady species 
een” nw crowding them, suppressing their branches, 
pruner. and possibly shading out the entire tree, 
unless the shaders are kept within bounds. The pruner 
must study these relationships, must protect the weaker, 
and must give them at least a free upper crown, if he desires 
to keep the groups in harmonious development. A little 
observation will soon show which trees are relatively weaker 
in their shade endurance. 
The most difficult task of the pruner, because requiring 
the most judgment, a sense of fitness, and a clear concep- 
tion of the results of his pruning, is that of training trees 
to desirable outline. This refers, of course, to single trees 
on the lawn, where the form and 
outline of the crown are the 
important features. 
The “natural,” symmetrical 
form, typical of the particular *!*- Saged oa 
species, is, to be sure, the ideal 
one to be attempted in general. But it is by no means 
certain that the individual tree will. if left alone, develop 
this form. Not only do conditions of the soil, which influ- 
ence the root development, find expression in the shape of 
the crown, leading to irregular and sometimes undesirable 
