GRAFTING 



103 



and it is principally used in working over old trees. It is 

 preferable to graft the smaller limbs which are better suited 

 to cleft grafting than to bark grafting. 



The top working of a tree is very important in many 

 instances. It enables the grower to change an inferior 

 sort to a good variety, after the tree has come into bearing. 

 Occasionally it is desirable to change a given variety after 

 the tree has become large. Top working the tree by cleft 



Fig. 48. — An apple tree top worked by cleft grafting. 



grafting is the only practical method. Sometimes varieties 

 are sterile and it becomes necessary to graft other fertile 

 varieties into these barren trees before any fruit will set. 



Whenever top working is practised to any great extent, 

 it is necessary to extend the operation over a period varying 

 from three to five years. A period of this length is necessary 

 because when a tree is severely headed back the balance 

 between the top and the root is broken. As a result of this 



