162 MASS. EXPERIMENT STATION BULLETIN 170. 



Manj' of the cavities in trees are caused by leaving long stulDs on the 

 trunk of the tree, which become infected and disintegrated, the decay 

 following back into the heart of the tree. (See Fig. 21.) It is therefore 

 essential that close pruning and antiseptic treatment of the wounds 

 should be practiced in order to prevent this decay. The plastic materials 

 in a tree will not follow up a long stump and form a callus unless there 

 are some branches left upon it which bear leaves, and even then healing 

 is most likely to take place only close to the living branch of the stump. 



Two or more cuts should be made when pruning practically all limbs 

 to prevent peeling, and on limbs of any size it is necessary to make the 

 incision on the under side for the same reason. (See Fig. 22.) After re- 

 moving the limbs with a saw, a mallet 

 and chisel may be used to sniooth up the 

 cut surface. This induces a better callus 

 growth. It is well to prune carefully at 

 the time of transplanting, when all street 

 trees should be trimmed to a height of 8 

 or 10 feet or more. It is usually necessary 

 at this time to prune for the purpose of 

 Ijalancing the root and branch system, 

 and when this is done some of the less 

 desirable branches may be sacrificed, and 

 those remaining may be cut back to some 

 extent, if necessary. However, a great 

 deal of unwise and careless pruning of 

 nursery stock and young trees is done, 

 and many specimens are ruined in this 

 way. Tree pruning shears should not 

 be used in a haphazard manner, and a 

 distinct idea of the object in view should 

 be borne in mind. Moreover, species 

 differ greatly in their response to mutilation, and what may prove of little 

 consequence to one may be quite injurious to another. 



The practice of topping trees is injurious, and should never be resorted 

 to except in special cases. All of the reserve material in the tree is stored 

 in the roots, stem and branches, and in a transplanted tree this is suf- 

 ficient to develop the foliage. It is necessary that a young transplanted 

 tree should have a certain amount of foliage for growth and development, 

 since the rapidity of growth is dependent upon leaf development. 



The type of trees termed "bean poles," having the tops so cut away 

 that there are no limbs left, is not suited, therefore, to transplanting. 

 Trees like the willow will survive any amount of mutilation, but elms, 

 maples and others must be handled more carefully to obtain the best 

 results. Pruning has a marked effect on the conformation of trees. 

 Pruning the branches or secondary organs directs the energies of growth 

 to the trunk, whereas topping, or the destruction of the leader, has the 



Fig. 23. — Formation of a cavity in 

 tree caused by the removal of a 

 large limb, and wound not prop- 

 erly cared for. 



