HEAD FORMATION IN APPLE TREES 157 



The r;.tl:cr light pruning followed in this experiment has not dwarfed the 

 trees nor decreased yields appreciably, except where heading hack the new 

 growth has been practiced. 



Heading hack the new growth has removed more wood, made a denser top, 

 favored a more upright growth, and dwarfed the trees somewhat. It has also 

 delayed the start of shoot growth slightly and distinctly prolonged the growing 

 season of the shoots. It slightly increased the rate of shoot growth and 

 checked cambial growth. It decreased bloom and yield as long as it was prac- 

 ticed. It caused the growth of a greater number of shoots the year follow- 

 ing pruning. 



The globular headed tree was most successfully produced, but this type is 

 not desirable. The central leader tree failed in many cases, especially where 

 the side branches were not headed back, most of these becoming modified 

 leader trees. Most of the unpruned trees could be classified as modified leader 

 trees. This may, perhaps, indicate that the modified leader type is the natural 

 form for most varieties of apples. If one desires to produce a central leader 

 tree, vigorous vegetative growth and pruning the scaffold branches are 

 necessary. 



Interpretation of Experimental Evidence 



It is perhaps true that nmch of the pruning in the past was worse than no 

 pruning. It would be better to leave the young tree unpruned than to cut it 

 back severely and without discrimination. If, however, the tree is pruned 

 lightly and with understanding, growth may iie controlled and directed toward 

 the production of more satisfactory and uniform trees than would result if 

 they were left to themselves. 



The Purpose of Pruning 



In order to prune intelligently, a clear understanding of the purpose of 

 pruning is necessary. This may be outlined under the following heads: 



1. To produce a well balanced, mechanically strong tree. 



This means that the permanent scaffold brandies will be of al)out equal size, 

 well separated up and down, and evenly distributed around the leader or 

 trunk. One brancii should not be directly aljove another even if they are 

 separated by a considerable distance. It is probably not desirable to have 

 even two branches at the same height. Certainly three branches at tiie same 

 height will seriously dwarf the leader above and any scaffold branches arising 

 from it, resulting in a weak tree. 



Mechanical strength is secured by having the scaft'old branches originate 

 through a strong shoulder at the place of origin. To get this the branch 

 angles should be wide and tlie branch smaller at the point of origin than the 

 leader. The initial growth of the branch should not be too strong. Branches 

 coming out at a narrow or very acute angle are likely to develop layers of 

 bark between the branch and leader instead of a bridge of wood. The former 

 means a weak crotch that is almost sure to split with the first heavy crop of 

 fruit, while the latter gives a strong crotch that will not split. The Baldwin 

 tends to form narrow angles while Rhode Island Greening and Mcintosh tend 

 to form wider branch angles with bridges of wood across which give strength, 

 enabling the trees to carry heavy loads of fruit without splitting. 



2. To direct growth toward the production of the nuiximum quantity and 

 quality of fruit throughout the life of the tree. 



