346 



FUNDAMENTALS OF FRUIT PRODUCTION 



that very few orchard fruits have less than one chance in 10 of encoun- 

 tering frost. 



The data here presented arc introduced as suggestive rather than 

 for their absohite value. As pointed out elsewhere, a frost recorded as 

 "killing," though damaging to tender vegetation, may do little or no 

 damage to fruit blossoms; similar data based on the last occurrence of 

 30° or 29°F. would be of more direct value to the fruit grower. Neverthe- 

 less the general liability of certain regions to frosts damaging to fruits 

 holds true, whatever criterion be adopted, and though it would be hazard- 

 ous to apply the present data unreservedly to any one point they serve 



Fig. 35. — Computed dates when the chance of killing frost falls to 1 in 10. After these 

 dates killing frost will occur only 10 years in a century. {After Reed^^^) 



adequately for comparison between different points. Arranged on a 

 slightly different basis and in conjunction with accurate blossoming 

 charts, which are not available, they would have even greater value. 

 At present only generalizations are possible. The tendency of blossoming 

 to advance more rapidly in the central than in the Atlantic states and the 

 irregularity in the recession of last frosts, with a general tendency toward 

 faster recession on the Atlantic seaboard, makes a given fruit more 

 liable to frost damage in the Mississippi valley region than on the 

 Atlantic coast, if local variations do not intervene. 



INFLUENCE OF SITE ON MINIMUM TEMPERATURES 



The air in the neighborhood of radiating surfaces has been shown to be 

 cooled by conduction and the air temperature on a still night to increase 

 with distance from the surface. As the air in contact with radiating 



