276 NEBRASKA STATE HORTICULTURAL SOCIETY. 



or 3 degrees below the freezing point. Just at this stage the 

 apple is perhaps in more danger than the peach, apparently 

 for the reason that the fruit is borne on long stems which 

 seem peculiarly susceptible to injury from cold. From now 

 on after the flowers have been fertilized, with the petals 

 dropped, and the young fruit increasing in size, the slender 

 stems which support the apples are unable to resist a temper- 

 ature lower than the freezing point. At tliis stage it is a 

 curious fact that the apples seem to be more hardy than their 

 stems, but if the latter are injured of course the fruit also 

 suffers. 



In giving danger points for the various stages of develop- 

 ment in both the i^eaeh and apple the writer has tried to be 

 conservative, lilxperience in artificially freezing thousands 

 of peach buds has shown that in the various stages mentioned 

 they will often withstand lower temperatures than those 

 given as danger points. However, so far as the practical 

 fruit grower is concerned, the figures will serve him as a 

 guide as to when the fires in the orchard Should be lighted. 



TRACTICABILITY OF USING ORCHARD HEATERS UNDER MISSOURI 



CONDITIONS. 



The good results which have been attained by the use of 

 the orchard heaters in Colorado have almost always been in 

 the valleys. A gTeat many of the orchards in Missouri, both 

 peach and apple, are planted on high ground which is often 

 rolling. Since cold air is heavier than warm air, and there- 

 fore has a tendencv to drain awav from the high ground to 

 the lower levels, the orchards located on high ridges and hill- 

 tops A\ould be much less apt to be endangered from frosts, and 

 hence there would be less necessitv for heating. AA'ai'm air 

 being lighter has a tendency to rise, and great loss of heat 

 from the fires Avhich are kept burning in the orchard results 

 because the air Avhen warmed may quickly rise above the level 

 of the trees. This is particularly true of still, cold nights 

 when frosts are likelv to occur. When the wind is blowing 



