INJURIES TO SHADE TREES 151 
mutilation of roots. Such injuries require immediate 
attention. The injured parts must be removed or freed 
from ragged edges to facilitate the process of healing, and 
in extreme cases by a corresponding trimming of the top, 
to reduce the foliage demands to correspond with the 
lessened power of the root system. In planning construc¬ 
tion work which threatens damage to the roots of trees, 
the harm may frequently be averted by suiting the plan 
of work to the existence of trees. Contractors should not 
be allowed to excavate near a tree, for any purpose, with¬ 
out the approval of the civic authorities. If the commun¬ 
ity has a shade tree department, the entire work should 
be under the supervision and control of that branch of 
the local government. Through consultation and cooper¬ 
ation—and through compulsion, if need be—much damage 
can be prevented. In underground construction, and even 
in widening a street or changing a grade, it is often possible 
to modify plans in a way to save trees which would have 
been sacrificed if there had been no municipal control. 
Underground damage does not always start below the 
surface, but it may come from above, as in the case of 
salt water from ice-cream freezers emptied near the base 
of the tree or calcium chloride or sodium chloride (common 
salt) applied to the surface of roads and walks to keep 
down dust. These substances are very injurious to the 
roots of trees and other plants, as is also water in which 
much of either is dissolved. Road oils also have to be 
handled carefully in the neighborhood of trees to prevent 
injury to the roots. Salt should never be used for melting 
ice or snow on a sidewalk near trees, as the brine thus 
formed will injure any roots that it reaches. Precaution is 
necessary in connection with drainage from mortar beds 
placed near trees. Water saturated with lime must not be 
permitted to reach nearby root systems, as the lime will 
cause serious injury. 
