PRUNING PRINCIPLES 115 



little that has not been known for a long time from the 

 standpoint of practice. Investigators, even if they have 

 not greatly enlarged our knowledge, certainly deserve great 

 credit for undertaking such tedious and painstaking work 

 as that discussed above. To a large extent, their findings 

 support pruning principles based upon plant physiology. 



106. 17. Fruitfulness may be induced by shortening ex- 

 cessive twig groivth, thus favoring the developrnent of fruit 

 buds and spurs. 



Since the vigor, the age and the method of handling the 

 tree and other local factors must be considered, therefore no 

 rule can be laid down as to how often or how much short- 

 ening-in may be done to secure productiveness. In propor- 

 tion as the practice tends to reduce production of woody 

 parts it favors the formation of fruit buds ; but when carried 

 beyond this point it may be equivalent to a severe pruning 

 and therefore may actually favor wood development. 



Fruit trees that are producing 1 to 1 J'2 feet of new growth 

 annually may have these growths reduced 25 to 35 per cent. 

 This statement is general enough to apply to cases other than 

 the development of fruit buds. It includes such other aims 

 as indirect fruit thinning, preventing dwarf trees from ex- 

 ceeding the development of their stocks, maintaining the de- 

 sired form and size of trees to suit the ideal of the grower 

 or the area available. So far as fruit bud development is 

 concerned, shortening-in of this kind may have small effect 

 if done only occasionally or spasmodically. 



The shortening-in of terminal twigs favors the develop- 

 ment of fruit spurs in the upper but interior part of the tree 

 tops, spurs which sooner or later develop blossom buds 

 (Fig. 173). The practice, fairly common in the commercial 

 production of dwarf pears, is perhaps properly one rather 

 of training for convenience than of pruning proper, and it 

 is doubtful whether or not productiveness, or shall we say 

 income, is enhanced by it. To be sure, the fruit may be 

 borne in a much more limited area than in the case of trees 

 not so treated. 



