26 MANUAL OF AMERICAN GRAPE-GROWING 



selecting a site near water, on slopes or in a warm thermal belt 

 must be exercised. 



The limits of grape culture are also determined by early 

 autumn frosts. The grape stands two or three degrees of 

 frost, but anything lower usually destroys the crop. Here, 

 again, the only precaution is to take pains in selecting the site. 



The use of weather data and dates of life events of the grape. 



These considerations of length of season, humidity and 

 spring and fall frosts make it plain that the grape-grower must 

 synchronize these phases of climate with the life events of the 

 grape. In particular, he must study weather data in relation 

 to the blooming and ripening of grapes. Usually, the neces- 

 sary weather data may be secured from the nearest local weather 

 bureau, while the date of blooming and ripening may be ob- 

 tained from the state experiment stations in the states where 

 the grape is an important crop. 



Winter temperature. 



Varieties of native grapes are seldom injured in America by 

 winter-killing, since they are usually planted in climates in 

 which wild grapes withstand winter conditions. Native vari- 

 eties follow the rule that plant and climate are truly congenial 

 in regions in which the plant thrives without the aid of man. 

 A few varieties of native grapes fare badly in the winter's cold 

 of northern grape regions, and the tender Vinifera vine is at 

 the mercy of the winter wherever the mercury goes below zero. 

 In cold climates, therefore, care must be exercised in selecting 

 hardy varieties and in following careful cultural methods with 

 the tender sorts. If other climatic conditions are favorable, 

 however, winter-killing is not an unsurmountable difficulty, 

 since the grape is easily protected from cold, so easily that the 

 tender Viniferas may be grown in the cold North with winter 

 protection. 



