CHAPTER XVI 

 WINTER INJURY 



Macoun'2o enumerates ten manifestations of winter injury in orchard 

 fruits, viz.: root-killing, bark-splitting, trunk-splitting, sunscald, crotch 

 injury, killing back of branches, black heart, trunk injury, killing of 

 dormant buds and winter-killing of swollen buds. As one form of bark- 

 splitting, Macoun includes a condition considered here as crown rot. 

 These forms may occur singly or in varying combinations; some are 

 products of severe conditions that almost of necessity entail other forms 

 characteristic of less severe freezing; some may be responses of varying 

 plant conditions to the same weather and some may be responses of 

 identical plant conditions to varying weather. Still other manifestations 

 are recorded occasionally. 



Conditions Accompanying Winter Injury. — Nine of the ten forms of 

 winter injury distinguished by Macoun ^^'^ appear above ground. This 

 diversity is due probably to a wider range of internal conditions in the 

 tops and to a wider range in above-ground environmental factors. It 

 may be attributed also to the greater facility with which top injuries are 

 studied; were observations of parts below ground more easily made, 

 what is now referred to simply as root injury might be found to consist of 

 several kinds. Above ground so diverse are the manifestations of 

 winter injury that the whole condition seems confusion confounded, 

 abounding in contradictions. Certain trees in an orchard suffer winter 

 injury and others do not. Excess soil moisture causes winter injury in 

 one instance and lack of soil moisture causes it in another. Cold leads 

 directly to winter injury yet sometimes high temperatures induce it 

 hardly less directly. At times young trees suffer more; at others, older 

 trees. Orchards in high wind-swept spots are damaged; again it is the 

 low-lying orchards that are afflicted. Late maturing trees suffer in one 

 locahty; somewhere else it is the early maturing trees. Now it is trees 

 weakened by neglect that lack hardiness; again it is the highest cultivated 

 trees that fail. An early winter freeze is the cause at one time; in another 

 case a late winter freeze brings destruction. An early freeze has been 

 known to kill peaches while pecans survived. 



Table 18, arranged from data assembled at the New York Agri- 

 cultural Experiment Station, at Geneva''*" and showing climatic condi- 

 tions at that point, is designed to show the varying conditions that may 

 induce or accompany winter injury. Unusual climatic features that 

 have, conceivably, a bearing here, are shown in heavy type. The 



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