20 



BULLETIN 205. 



should be gradually elevated by cutting back the lower branches 

 to one-half or two-thirds their length each year for two or three 

 years and then removing them entirely. In case several spring 

 from the same point on the trunk, one or two should be cut at a 



time, the others being kept 

 very short while the earlier 

 wounds are healing. In shap- 

 ing the top, select a leader and 

 make it as vigorous as possible 

 by trimming all strong shoots 

 near it and cutting back the 

 more vigorous side branches. 

 The proper form is best deter- 

 mined b*y the use of the den- 

 droscope with a dendrometer. 

 As the tree grows older, a few 

 more of the lower branches 

 will have to be removed and 

 possibly some of the upper 

 ones taken out to keep the top 

 from becoming too large or 

 too dense. 



The removal of large bran- 

 ches is always attended with 

 a certain amount of risk and 

 this risk is largely increased 

 when more than one or two are removed during the same season ; 

 but if the wounds are carefully dressed and borers kept out, decay 

 may usually be avoided, though the loss of food cannot be replaced. 

 An overgrown top should usually be corrected by thinning out 

 some of the longer branches. This is better than heading them 

 back, because the effect of the latter process is to destroy the 

 beauty of the tree and to produce a dense objectionable cluster 

 of branches as well as to open a sure road for the entrance of 

 disease. The cut end of a large branch rarely heals over, the 

 adjacent parts die, and decay gradually extends to the trunk. 



Certain large and vigorous trees that stand pruning particu- 

 larly well, such as the elms, lindens and sycamores, may best 



FIG. 22. Silver maple in Ithaca 

 " headed back." 



