124 The Commercial Apple Industry 



causes of crop failures. Official weather reports will as- 

 sist the investor in determining whether damp rainy 

 weather and days of low temperature are common during 

 the blooming period. A commercial project embracing 

 several thousand acres of orchard land has developed in 

 a region where frost occurs in practically every month of 

 the year and where the minimum temperature during the 

 blossoming time clearly indicates that frost-injury is un- 

 avoidable. An occasional dip in temperature to a point 

 slightly below freezing does not necessarily signify exces- 

 sive frost-injury, but recurring temperature at this criti- 

 cal period of 27 F. or lower is significant of probable 

 injury. 



The question of a particular site within a given region 

 very often has an important bearing on susceptibility to 

 frost-injury. A north or northeastern slope is usually 

 preferred on account of its tendency to retard growth in the 

 spring until danger has passed. Frost-injury is extremely 

 erratic at times, striking here and there in an almost in- 

 explicable manner. A fatal temperature on one occa- 

 sion may result in very slight damage at other times. 

 Other things being equal, higher elevation is preferable 

 on account of better air drainage, and also soil drainage. 

 The tendency of cold air to settle from high to lower land 

 makes pockets and valleys without broad outlets compara- 

 tively dangerous. An example is afforded in the Rogue 

 River Valley near Medford, Oregon. The orchards on the 

 higher land, known as the foothill orchards, are much less 

 susceptible to frost-injury than those on the floor of the 

 valley; sufficiently so that the practice of smudging, still 

 common in the latter orchards, has been largely discon- 

 tinued on the foothills. 



