PRUNING— THE SEASON 447 



winter pruning. In this way two steps in the construction of the franie- 

 work of the tree would be taken in one season and theoretically a year 

 would be saved in growing the tree to producing size and in bringing it 

 into bearing. This type of summer pruning, which includes both thin- 

 ning and heading early in the summer (about July 1) was studied with 

 apples in Oregon.-^ Though such varieties as Jonathan, Grimes, Yellow 

 Newtown and Wagener summer pruned in this way did not make the 

 equivalent of two seasons' ordinary growth in one summer, three success- 

 ive years of such treatment resulted in trees comparable in size, fruit 

 spur development and productiveness to winter pruned trees a year 

 older. In other words a j^ear had been gained in developing their frame- 

 work and in bringing them into bearing. Observation led to the belief 

 that this method of pruning is equally valuable in forcing the early de- 

 velopment of both pears and sweet cherries. This special pruning prac- 

 tice is desirable with young trees only under favorable growing conditions 

 when they are making new shoots at least 2}^ feet in length and where 

 the growing season is long enough to permit a proper maturity of the 

 late secondary shoots. 



Summer Pruning as a Conservation Measure. — It has been stated 

 before that the removal of any living portion of the top of a plant at any 

 time deprives the plant of a certain amount of elaborated food material. 

 This is true particularly of pruning in summer when the storage tissues 

 have been depleted for the building of new structures. However, the 

 removal of any portion of the top reduces somewhat the demand on the 

 root system for nutrients and moisture; under certain conditions this 

 reduction may enable the roots to supply the remaining parts with 

 amounts nearer their requirements for growth. In this way pruning 

 can be said to have a stimulating influence. In other words, it may be 

 regarded as a conservation measure, making given amounts of moisture 

 and nutrients go further; because these larger amounts of materials are 

 available, certain parts may manufacture and store more elaborated 

 foods than they could otherwise. This may be considered a concentra- 

 tion effect. The concentration is limited to certain parts and in some 

 instances other parts may suffer and perhaps the plant as a whole may be 

 weakened. Apparently one of the more important objects that may be 

 accomplished by pruning during the growing season is due to this in- 

 fluence. 



This effect of summer pruning depends on many factors. Among the 

 more important are: (1) the severity of the pruning, (2) its kind, (3) the 

 exact stage of development of the plant at the time the pruning is done 

 and (4) the soil conditions before, at the time of and after the operation. 



Independent of the other factors, it is evident that, within certain 

 limits, the more severe the pruning the greater will be its effect in diverting 

 into the remaining parts nutrients and moisture. However, a point is 



