WINTER INJURY 279 



of soda or sulfate of ammonia, as a means of stimulating 

 growth. Thorough cultivation should, of course, be followed 

 when conditions permit. 



Special repair work may also be necessary, such as bridge- 

 grafting and cleaning and disinfection of the wounds.^ 



249. Variation in hardiness of fruits. — While the vari- 

 eties within any given kind of fruit vary widely in hardiness, 

 yet there is a rather marked difference between species and 

 genera of the common fruits. The apples as a class are the 

 most hard}'' of the commonly grown tree-fruits, followed by 

 the American plums, Japanese plum, sour cheriy, European 

 plum, pear, sweet cheriy, apricot, and peach. It is true 

 that the currant and gooseberry and certain species of Amer- 

 ican plums are more hardy than the apples. There is so 

 much variation in different localities and in different sea- 

 sons, however, that such a classification cannot be con- 

 sistent. 



250. Hardy and tender varieties, — As with the different 

 s])ocies and genera, so the varieties of fruits are variable in 

 hardiness, depending on a multitude of conditions.^ The 

 following lists are an attempt to rate some of the more com- 

 monly grown varieties, the hardiest being in the first column 

 and those in the other columns decreasingly hardy. 



1 Purdue Univ. Agr. Exp. Sta. Circ. 87. 1918. 



- XI. S. Dept. Agr. Bur. Plant Ind. Bull. 151. 1909. Fruits recom- 

 mended by the American Pomological Society for cultivation in the 

 various sections of U. S. and Canada. 



