WINTER INJURY 263 



ten ^ and Howard - in this country. This phenomenon can be 

 observed with different varieties of the same kind of fruit by 

 the early swelling of buds and time of starting into growth. 

 For the more southern peach-growing sections that are in 

 the danger belt for spring frosts, the length of the rest-period 

 becomes of serious importance, for the more forward vari- 

 eties are most likely to be lost from freezes and frosts. In 

 order to shift the resting-period to later in the winter, a 

 series of experiments were conducted by Whitten to cause 

 the trees to enter their rest-period at a later time and hence 

 make them correspondingly later in awakening from this 

 state. By means of late cultivation, it was possible to delay 

 the rest-period and as a result the trees were a few days later 

 in blossoming than was the case under normal conditions. 



FACTORS INVOLVED IN FREEZING 



234. Maturity. — Reference has already been made to 

 the importance of having the tissues well matured if injury 

 from low temperatures is to be avoided. It has been estab- 

 lished experimentally ^ as well as by extensive observation 

 that maturity is the most important single factor involved. 

 While the nature of the season is beyond the control of man, 

 certain horticultural practices should be followed in order 

 to bring about as great a degree of maturity as possible. 

 These will be considered later. 



It has been observed that the hardiest varieties mature 

 early in the season. Macoun has studied the effect of winter 

 on a large number of plants at Ottawa, Canada, for a period 

 of twenty-two years, having under his obsei-vation over 

 3000 species and varieties, many of which kill back more or 



1 Whitten, J. C. Mo. Agr. Exp. Sta. Bull. 38. 1897. 



2 Howard, W. L. Mo. Agr. Exp. Sta. Res. Bull. 1. 1910. 



' Neb. Agr. Exp. Sta. Bull. 79 and 92. 1903, 1906. Ohio Agr. Exp. 

 Sta. Bull. 192. 1908. N. Y. (Geneva) Agr. Exp. Sta. Bull. 269. 1905. 



