BULLETIN 231] 



WALNUT CULTURE IN CALIFORNIA. 



231 



large limbs, exposing a large surface of wood to decay and also making 

 the growth of the scions somewhat less certain than if they are inserted 

 in smaller limbs. Usually cuts of 3 or 4 inches in diameter are the 

 most desirable size, although larger and also smaller cuts can be grafted 

 with more or less success. In grafting over orchard-planted black wal- 

 nut trees it is not usually advisable to graft them before they have a 

 diameter of at least 3 inches at the point of grafting, and 4 inches is 



FIG. 34. Views of four different sides of scion for top-grafting by side cleft method. 



even better. If the trees are grafted while quite small, the tops are 

 likely to greatly outgrow the trunk and form a topheavy, undesirable 

 form of tree. In working over trees in the top less time and fewer 

 scions are required if the limbs are cut well back toward the main forks, 

 making fewer stubs to work upon, than if the limbs are cut off further 

 out where the branches are more numerous. In the latter case, how- 

 ever, the chances of success are somewhat better than when the work 



