142 
TREES AS GOOD CITIZENS 
Since the object of pruning is to promote vigorous 
and symmetrical growth, it is well to be guided by the 
principle that the aim is to produce a primary frame 
toward the center, with a surrounding framework. The 
primary frame will consist of one or more main branches 
from the stem, while about this will be several smaller 
branches grouped in a way to form a symmetrical outer 
framework. The primary frame should be in harmony 
with the habits of growth belonging to the particular 
species. Branches which do not conform to the character¬ 
istic shape of the species, and cannot be made to conform, 
should be removed. Branches which develop too rapidly 
to harmonize with the general framework may be held in 
check by removal of their ends. These steps develop 
the tree along lines in keeping with the natural growth of 
the species. This is always desirable, since pruning is not 
intended to alter the normal form of the tree. The 
best pruning is that which leaves the tree most natural in 
appearance, and in the long run makes it look as if it had 
not been pruned at all. An exception to this general rule 
is to be made, of course, in trees trimmed into formal 
shape and small size for narrow, crowded streets. Trim¬ 
ming for this type of trees should always be done by an 
expert. 
It is important that the trees should have a proper 
height of branching above ground and that the trees 
should be uniform in this respect. To achieve this it is 
necessary to pursue a policy of gradual removal of the 
lower branches. The removal of the lower branches 
should proceed with the growth of the tree from year to 
year, so that within a few years there will be 10 or 
12 feet of the trunk free from branches. This height is 
necessary in street trees for the freedom of traffic, and 
it is also important in the matter of appearance. Trees 
