316 The Principles of Fruit-growing 



are somewhat more resistant to cold than has been reported by 

 observers from other parts of the United States. The data further 

 show that the degree of resistibility to frost varies with different 

 stages of growth. The peach is least resistant when it is about the 

 size of a pea, when the calices are falling off. Contrary to the findings 

 of other observers, the bloom is not the most tender stage of growth. In 

 other words, the data indicate that the newly set peach is more deli- 

 cate than the newly opened blossom. In the majority of cases, a 

 temperature of 26, lasting only a short time, did little or no in jury- 

 to the opening bud, newly opened blossom or newly set fruit of the 

 peach, native plum, pear and apple; while one-half a degree below 

 this, or 253/6, although lasting only a few minutes, killed a large 

 percentage of the opening buds, newly set blossoms and young 

 fruits of the peach, in a number of cases. In other words, 26 was 

 the danger-point and any temperature below this is liable to do 

 more or less injury, depending on how low it gets and how long it 

 remains at that temperature. In some cases, however, a temperature 

 of 24, lasting only a short time, left about 25 per cent of the blooms 

 and 9 per cent of the newly set fruits uninjured. 



Three important factors that influence the amount of damage 

 done by spring frosts are: The degree of killing temperature, the 

 time of day at which it occurs, and the length of time the temperature 

 remains below the danger-point. ... As the young fruit develops, it 

 seems to get more tender, until it grows beyond a certain size, when 

 it seems to get hardier again; so that the later frosts which come after 

 the young fruits have made quite a growth are liable to do more 

 injury than the same degree of cold in the earlier part of the season, 

 when the fruits are less developed. At this stage of growth, 26^ to 

 27 would probably be dangerous to peaches. The very late frost 

 of 25 on May 4, 1912, killed practically all the peaches in the 

 experimental orchard, while 24% on April 17, 1910, left about 

 30 per cent of the Elbertas. 



"On the whole, apples and pears seem to be more resistant than 

 peaches and plums." 



All the studies of this subject indicate that local con- 

 ditions greatly modify the effect of cold, and probably no 

 generalizations can be made that will warrant a grower in 

 withholding smudging or fires when the mercury indicates 



