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 injured 



by insects. 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 

 young elm trees have 

 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. 



FIG. 98. A Red-Oak Tree in the Harvard 

 University Yard 



Three months after planting 



