72 
TREES AS GOOD CITIZENS 
center row most satisfactorily. Including tree strips the 
sidewalks on Pennsylvania Avenue are 20 feet wide, 
and each of the two roadways 38 feet, leaving 44 feet 
for the parking strip. 
With streets less than 150 feet wide, it is desirable to 
use small trees, shrubs or evergreen bushes, instead of 
trees, for the center planting. Fine park effects may be 
obtained with these. 
(4) The Center Strip.—For narrow streets without 
car tracks, where the buildings restrict the admission of 
light, and traffic needs suggest a double roadway, a single 
row of trees in the center of the driveway may be advis¬ 
able. An abundant supply of light and sunshine is 
essential to the best development of trees. To place trees 
along the curb of a street where sunshine is in scant sup¬ 
ply robs the trees of their chance for proper growth. In 
general terms, trees cannot be at their best unless their 
distance from the building line is at least equal to half 
the height of the buildings. In some streets this cannot be 
achieved with trees along the side of the roadway, and the 
center strip offers the solution. 
It may sound contradictory, but the single strip of 
trees in the center is used for broad thoroughfares as 
well as for those which are too narrow for sidewalk 
plantings. A street may be 100 feet in width and yet 
have sidewalks too narrow for trees; so narrow that to 
place trees along the curb would result in shutting off 
light and air from the buildings. By placing the trees 
in a central row, the decorative and shade-giving qualities 
are obtained, and the trees have the chance for vigorous 
growth which would be lacking if they were placed on the 
narrow sidewalks. Two central rows, of course, are better 
than one and should be planted where space and traffic 
conditions permit. 
