1911.] PUBLIC DOCUMENT — No. 31. 181 



sections of the temperate zones. The apple achipts itself under 

 cultivation to a considerable range of rainfall, and in districts 

 of deficient precipitation irrigation is practiced. Therefore, 

 the question of rainfall has comparatively little weight in the 

 general cultivation of the apple. Sunshine has considerable; 

 effect, but it is not a limiting factor anywhere in the apple belt. 

 The great clinuitic factor which limits the distribution of apples 

 in general, and of the different varieties in particular, is tem- 

 perature. 



Over the greater part of the i^orth American continent the 

 northern limit of successful apple growing is fixed by the min- 

 inuim winter temperature. Different varieties of the common 

 a})ple vary greatly in their ability to withstand minimum win- 

 ter temperatures, and the condition of the tree, particularly as 

 regards moisture content at the time minimum temperatures 

 occur, has great influence in determining whether the tree 

 survives. Very few, if anv^ varieties will withstand a tem- 

 perature much below — 40° F. without being killed back more 

 or less. In many cases a considerably less severe temperature 

 is fatal to even the hardiest varieties. With the possible excep- 

 tion of the extreme northern Pacific coast, under conditions of 

 a maritime climate, there is nowhere in ISTorth America a region 

 where certain varieties will not produce fruit in summer, pro- 

 vided they can withstand the cold of winter. In other words, 

 the summers are warm enough to mature fruit of short-season 

 varieties, provided the winters do not kill the tree before it has 

 reached the bearing age. 



The a]iple does not succeed in the southern portions of 

 North America, although fruit may be produced in every State 

 of the Union, and probably in portions of Mexico. The diffi- 

 culty in the way of the southern extension of apple growing 

 seems to be largely the heat during the summer. The trees fail 

 to grow during hot periods in the growing season, and fail to 

 set, or at least to mature fruit. The latter is especially true of 

 winter sorts, and many varieties grown in the south are short- 

 season ones, which are able to mature fruit before the hot pe- 

 riods of Tulv and August arrive. 



