182 MANUAL OF AMERICAN GRAPE-GROWING 



and violacea, Cipro nero, Dattier de Beirut, Cornichon, Emperor, 

 Black Ferrara, Malaga, Olivette de Cadenet, Pis-de-Chevre 

 blanc, Schiradzouli, Zabalkanski. 



These lists must not be taken as indicating absolutely for 

 all cases how these varieties are to be pruned. They simply 

 indicate their natural tendencies. Certain methods and con- 

 ditions tend to make vines more fruitful. Where these occur, 

 shorter pruning than is indicated may be advisable. On the 

 other hand, other methods and conditions tend to make the 

 vines vigorous at the expense of fruitfulness. Where these 

 occur, longer pruning may be advisable. 



The more usual factors which tend towards fruitfulness are : 



Grafting on resistant vines, especially on certain varieties 

 such as those of Riparia and Berlandieri ; 



Old age of the vines ; 



Mechanical or other injuries to any part of the vine ; 



Large development of the trunk, as in the cordon systems. 



The more usual factors which tend towards vigor at the ex- 

 pense of fruitfulness are : 



Rich soil, especially large amounts of humus and nitrogen; 



Youth of the vines; 



Excessive irrigation or rainfall (within limits). 



In deciding what system of pruning to adopt, all these factors, 

 together with the nature of the vine and the uses to which the 

 fruit is to be put, must be considered. It is best when the 

 vineyard is started to err on the side of short pruning. While 

 this may diminish slightly the first one or two crops, the vines 

 will gain in vigor and the loss will be made up in subsequent 

 crops. If the style of pruning adopted results in excessive 

 vigor of the vines, it should be gradually changed in the direc- 

 tion of longer pruning with the object of utilizing this vigor in 

 the production of crop. 



This change should be gradual, or the risk is run of injuring 

 the vitality of the vines by one or two excessively heavy crops. 



