BULLETIN 210. IMPERIAL VALLEY SETTLERS' CROP MANUAL. 203 



are easily broken or detached from the pedicle by a touch. The last 

 irrigation before gathering the crop, therefore, should not be later 

 than the commencement of ripening. If the irrigation and cultiva- 

 tion has been properly done up to that point the soil should contain 

 enough moisture to bring the grapes to the shipping point of ripeness. 



Second: A vine, for the best results, should have a dormant or 

 resting period. In the tropics, where the atmosphere is constantly 

 warm and the soil constantly moist, the vine becomes an evergreen. 

 The grapes produced under these conditions are of poor quality, 

 deficient in sugar and flavoring. The growth of the vine is not 

 checked completely by cold until the mean daily temperature falls 

 below 48 F. The mean daily temperature for December, the coldest 

 month at El Centre in 1909, was 50.25 F. If this alone controlled 

 the dormancy the vine should remain evergreen. There are, however, 

 one or two days each year, usually in December or January, when the 

 temperature drops to the freezing points or a few degrees below. This 

 is sufficient to make the vine lose its leaves and remain dormant for a 

 short time before the new buds swell. 



For the best results the vine seems to need about three months rest. 

 In order to insure this, the vine should commence its dormant season 

 before the December or January frost. This can be controlled by 

 suitable management of the irrigation. 



When the moisture content of the soil falls below a certain per- 

 centage the rine ceases to grow. When the soil becomes still dryer 

 the leaves turn yellow and fall and the vine becomes dormant. The 

 irrigation should be so applied, therefore, that the vines are caused 

 to become dormant by drying of the soil, sometime in November. The 

 drying of the soil should not be too early or too intense or the vines 

 may be injured. 



After the grapes are gathered a very important part of the work 

 of the leaves still remains to be accomplished. This work is the 

 ripening of the young canes and the laying up of stores of starch in 

 the buds and other organs of the vine. It is on the abundance of these 

 stores that the growth and crop of the following year depend. 



This laying up of winter stores by the action of the leaves requires 

 a month or six weeks and takes place most abundantly when the vine 

 is provided with a large number of mature green leaves but is making 

 little or no new growth. In some cases an irrigation immediately 

 after the gathering of the grapes would be necessary or advisable to 

 prevent the premature dropping of the leaves. 



