178 SCHOOL AND HOME GARDENS 
All of the above are satisfactory for street or yard 
shade, where large trees are needed, although some of 
the quick-growing varieties are more easily broken by 
strong winds and are also more likely to be imjured 
by msects. The hard 
maple and the oaks 
make better trees 
and are not injured 
severely by insects. 
Give them their na- 
tive soil as nearly as 
possible. 
The large elms that 
have stood in the 
Harvard University 
campus for a century 
or more have nearly 
all been destroyed 
by insect pests. Some 
Fie. 98. A Red-Oak Tree in the Harvard young elm trees have 
University Yard 2 
Three months after planting been set out TeMpo- 
rarily. Elms thrive in 
ordinary soil composed of sand and gravel. For perma- 
nent trees the slower-growing red oaks are being planted. 
To prepare the soil for these, the sand and gravel is 
dug out, leaving a hole five feet deep and twenty feet 
in diameter. The excavation is filled with woodland soil 
and left to settle all winter; the following spring. while 
the wood is in a dormant condition, the trees are planted. 
