420 



FUNDAMENTALS OF FRUIT PRODUCTION 



out is therefore more severe in one respect and less severe in another. 

 If the pruning is comparatively heavy the difference is slight, but if the 

 pruning is light the difference is correspondingly greater. 



Observation shows that when growth begins the terminal and sub- 

 terminal buds are usually the first to start and in the majority of decidu- 

 ous trees and vines (less frequently in shrubs) they produce the longest 

 and strongest shoots, though shoots may grow from many of the lower 

 buds. However, seldom do all the lateral buds start and as a rule the 



Fig. 50. — Grimes apple tree, showing a typical response to heading back. Compare with 



Fig. 51 



largest percentage of those that remain dormant are on the basal portion 

 of the shoot. Those species that bear principally on spurs form these 

 spurs mainly from buds on the median and terminal portions of the 

 shoot. Heading back, therefore, limits fruit spur formation to a greater 

 extent than a correspondingly heavy thinning out. This is obvious 

 from the data presented in Table 11, showing the amounts of shoot 

 growth and the numbers of spurs formed by vigorous 5-year-old apple 

 trees of different varieties that had been headed back or thinned out 



