70 APPLE GROWING IX CALIFORNIA. 



CHAPTER XII. 



INJURY AND PROTECTION OF APPLES FROM FREEZING. 



It has already been stated that one of the chief limiting factors in 

 the production of apples throughout the various states of the Union is 

 frost. It is true that there are certain sections of the country where 

 frosts have seldom or never occurred to the detriment of the fruit crop. 

 Experience of orchardists in California and elsewhere has led to the 

 conclusion that no section, no matter how free it has been from killing 

 frosts during the danger period of trees in the past, can be said to 

 possess immunity, and there may come a time when the temperature 

 will drop so low that buds, blossoms and fruit, if not trees, must suc- 

 cumb. There are, of course, many places where fine fruit is grown dur- 

 ing favorable seasons that are visited by killing frosts periodically, and 

 the chances for and against raising a crop are about even. Such sections 

 do not offer the best advantages for commercial orcharding unless some 

 practical means of protecting the crop during the danger period may 

 be employed. 



PERIOD OF GREATEST DANGER FROM KILLING FROSTS. 



In the case of apples, the injury is usually done either to the buds, 

 blossoms or small fruit in the early spring, about blossoming time, 

 although a severe freeze during the winter season may kill the buds, 

 which often stand temperatures ranging from ten to thirty degrees or 

 more below zero. The period of greatest danger corresponds very 

 closely to the time from when the buds begin to swell in the spring 

 until the fruit has reached a diameter of a half inch. This time is, 

 of course, subject to variations in climate, due to altitude or local 

 conditions. 



BUD INJURY. 



Winter or early spring injury to buds may be detected by a discolored 

 area seen in the center upon cutting them open. The pistil or central 

 organ of the blossom is usually the first part to freeze and, once frozen, 

 fertilization is rendered impossible. Blossoms so injured will sometimes 

 develop, and the trees will come out in bloom and be just as beautiful 

 as if nothing had happened. An examination of such blossoms will show 

 the blackened pistil in the center. A peculiar form of freezing of apple 

 blossoms, which has come to my notice in another state, destroys the 

 petals entirely. The rest of the parts of the blossom develop normally, 

 fertilization takes place as usual, and a good crop of fruit may set 

 on the trees. 



FRUIT INJURY. 



Often fruit develops from frost-injured blossoms, but as a rule only 

 when fertilization has taken place prior to the injury. In Bulletin 91 

 of the Montana Experiment Station, Prof. O. B. Whipple gives an 

 interesting account of the parthenocarpic development (development 

 without fertilization) of apples, most of which were seedless and core- 



