STREET TREES. 55 
this defect, but when it exists in mature trees it is frequently advisable 
to connect the branches by a strong chain (fig. 18) in order to prevent 
the limbs from being torn apart. | 
FEEDING. 
It is difficult to do anything to stimulate the growth of street 
trees after they are once started, because usually the only uncovered 
area over the roots is the small opening immediately about the tree; 
hence, the importance of supplying the best of soil well enriched at 
the time of planting. - Sometimes a stimulation is desirable, which 
can be accomplished by dissolving one-half to 1 pound of nitrate of 
soda in 50 gallons of water and applying from 1 to 25 gallons of the 
liquid, depending on the size of the tree. Unless the soil is damp at 
the time of application water will be needed immediately afterward. 
This material should be applied only when the tree is in full leaf and 
growing. If applied when the tree is dormant it is likely to be 
leached from the soil before it is absorbed. If applied late in the 
season, that is, within three months of freezing weather, it would 
likely stimulate a late growth that would be liable to be killed the 
following winter and might make the whole tree more susceptible 
to injury from cold. 
Water is one of the great needs of city trees, as the ground surface 
is often almost completely roofed over with water-tight coverings. 
Itis usually a help for the pavement washings to drain into the parking 
space where the tree is planted. If acurb is placed about the parking 
space, frequent, regular watering is necessary where the ground is 
thoroughly covered with water-tight pavements. 
Where growing under suburban conditions, that is, with streets 
partially pervious to water, liberal parking spaces, and adjoining 
lawns, street trees will respond to all extra care given the near-by 
open spaces, whether parkings, lawns, or gardens. If these are well 
cared for the trees should have ample sustenance from them without 
any direct applications. 
In order to prevent the soil about a tree from being packed too 
hard by trampling it is frequently desirable on business streets to 
cover the soil about it with an iron grating. 
SPRAYING. 
Street trees, like all other forms of vegetation, are subject to attacks 
of insects and diseases. Because of the unfavorable conditions under 
which they grow, spraying for biting and sucking insects and suitable 
treatment for borers or other burrowing insects require especially 
careful attention. 
In addition to a number of troubles common to street trees in gen- 
eral, each species is lable to troubles of its own; hence, the need of 
~ competent supervision by a trained man with an efficient outfit 
rather than leaving the work to individual initiative. 
