334 PRINCIPLES AND PRACTICE OF PRUNING 



Figure 290 b, an improvement on the last system, differs only in the 

 method of treating the fruit canes. These are bent over in the 

 form of a circle and tied by their middle part to a stake which may 

 be smaller and lower than that needed for the vertical canes. This 

 bowing of the canes has several useful effects. The change of di- 

 rection moderates the tendency of the vigor of the vine to expend 

 jtself only on the terminal shoots. More shoots therefore are formed 

 on the fruit canes and as their vigor is somewhat decreased they 

 tend to be more fruitful. The slight mechanical injury caused by 

 the bending operates in the same direction (104). 



The excess of vigor thus being diverted from the fruit canes 

 causes the renewal spurs to form vigorous shoots, which soon grow 

 above the fruit shoots and obtain the light and air they need for 

 their proper development. This method is used successfully for 

 certain wine grapes such as Riesling, Cabernet and Semillon. It is 

 unsuited to large, vigorous varieties or for vines on rich soil planted 

 wide apart. In these cases two fruit canes are usually insufficient 

 and, if more are used, the grapes and leaves are so massed together 

 that they are subject to mildew and do not ripen evenly or well. 

 The bowing and tying of the canes require much skill and care. 



The body, arms and annual pruning of the system shown in 

 Fig. 265 are similar to those of Fig. 288, with the exception that the 

 arms are given a fan-shaped arrangement in one plane. It differs 

 in the disposal of the fruit canes, which are supported by a trellis 

 stretching along the row from vine to vine. This method, largely 

 used for the Sultanina (Thompson's Seedless), is the best system 

 for vigorous vines which require long pruning, wherever it is pos- 

 sible to dispense with cross cultivation. It is also suitable for any 

 long-pruned varieties when growing in very fertile soil. 



The vertical cordon system consists of an upright trunk 4^ feet 

 high with short arms and fruit spurs scattered evenly and sym- 

 metrically from the top to within 15 inches of the bottom. This 

 system is used in many Emperor vineyards in the San Joaquin 

 valley. Its advantages are that it allows the large development of 

 the vine and the large number of spurs which the vigor of the Em- 

 peror demands, without either crowding the fruit by the proximity 

 of the spurs or spreading the vine so much that cultivation is in- 

 terfered with. It also permits cross cultivation. 



One of its defects is that the fruit is subjected to various degrees 

 of temperature and shading in different parts of the vine and the 

 ripening and coloring are often uneven. A more vital defect is that 

 it cannot be maintained permanently. The arms and spurs at the 

 top of the trunk tend to absorb the energies of the vine and the 

 lower arms and spurs become weaker each year until finally no 

 growth at all is obtained below. After several years, most of the 

 vines therefore lose their character of cordons and become simply 

 headed vines with abnormally long trunks. 



The cordon can be re-established in this case by allowing a vigor- 



