THE PHYSIOLOGY AND PATHOLOGY OF PRUNING. 209 



THE PHYSIOLOGY AND PATHOLOGY OP PRUNING. 



BY FRANK WILT^IAMS, TECUMSEH. 



The question often arises, why do we prune? To answer this 

 question we need only visit a neglected orchard or grove of 

 shade trees. We find that trees often suffer from mechanical 

 injuries which they receive in --'arious ways. The more common^ 

 are those received from storms, animals and insects. To re- 

 pair these wounds, it is often necessary to regulate the growth 

 by taking away certain of the old limbs and adding new ones. 



The crown of a tree which is left to develop naturally, often 

 assumes a form which is disadvantageous. It produces such a " 

 number of branches that it becomes too thick at the center. 

 This shuts out the light which is essential to the formation of 

 plant food in the leaves. Then again we often find a large num- 

 ber of water shoots produced, which hinder the growth of the 

 tree, or may even stop it for a time. Therefore, it is necessary 

 to prune to regulate the crown and take away the "water 

 shoots." 



A tree cannot be removed from a nursery row without having 

 a large number of its roots cut or broken. This diminishes the 

 root system while the top is not changed. Thus if the top is 

 not pruned the diminished root system will have to supply the 

 entire top, which it cannot do satisfactorily. 



There are circumstances under which pruning is harmful, es- 

 peciaUy if large branches are removed. The removal of large 

 branches, while it may not cause a direct shock to the vitality 

 of the tree, often exposes dangerous wounds. It perhaps opens 

 the tree so much that some of the remaining parts sunscald, 

 and borers and insects gain a foothold; it may also destroy the 

 beauty and symmetry of the tree. Such branches represent a 

 certain amount of energy which should have been directed to 

 some part of the tree where it could have been used in building 

 up structure which would benefit the tree. 



My attention is often called to the abominable work of the 

 would be pruners who go about our cities horribly mutilating 



