268 UNIVERSITY OF CALIFORNIA EXPERIMENT STATION 



While the above instances would indicate that considerable pro- 

 tection might be obtained from running water through a grove during 

 a freeze, it should be stated that, in very many instances, little dif- 

 ference could be seen between the groves that were under water and 

 those that were dry, and in but few cases did the trees under water 

 show any greater vigor in putting out new growth. 



In general it seems that one should not rely upon the use of run- 

 ning water to protect the fruit from freezing. In case of emergency 

 no harm will come from running it, and if the temperature does not 

 go too low a slight benefit may result. 



Effect of Spraying Water on Trees. In a few places, and on a 

 few trees only, water was sprayed upon trees in order to keep them 

 from freezing. This soon gave the trees a heavy coating of ice, and 

 spraying was stopped so that the ice would not become thick enough 

 to break the limbs. In the few cases which were found where this 

 spraying had been done the practice seemed to have little value. 



In the case of seed-beds or small nursery stock that would not be 

 injured by a heavy coating of ice this method of protection might be 

 very effective. In a freeze, such as that under consideration in 

 California, it may be questioned whether the injury that would be 

 caused by such a protective treatment would not in general be as 

 great as the damage resulting from the frost injury. Again, it will 

 never be possible for all groves to have a sufficient supply of water 

 for such protection at the same time, unless a reserve water supply 

 is retained in special reservoirs for each grove. 



Effect of wrapping Trees. The difficulty of artificially heating a 

 young grove is greater than with older groves, where the trees are 

 larger and the hot air is more easily retained. The results obtained 

 by .wrapping the trunks of young trees are therefore of much practical 

 importance, for if there are ways of protecting young trees which are 

 cheaper than heating the best of these ways should be known. 



The principal substances used during the freeze for trunk wrap- 

 pers were cornstalks, tule, newspapers, and tar paper. Many young 

 trees had protectors about their trunks made of yucca, tar paper, or 

 perforated paraffined paper. These protectors are rectangular pieces, 

 which had been bent around the trunks, forming hollow cylinders, 

 there being an air space between the trunk and the protector. They 

 had been put around the trees during the summer to prevent the 

 sunburning of the bark or its mechanical injury, and were not gener- 

 ally regarded as frost protectors. 



Cornstalks afforded a good measure of protection when enough of 

 them were used, and when they were bound firmly enough to keep 



