A STUDY OF THE EFFECTS OF FREEZES 

 ON CITRUS IN CALIFORNIA* 



BY H. J. WEBBER AND OTHERS 



CONTENTS 



PAGE 



INTRODUCTION 247 



I. A STUDY OF THE FREEZE OF 1913 IN CALIFORNIA BY C. S. MILLIKE.V, A. R. 

 TYLOR, W. W. BONNS AND H. J. WEBBER 



Methods of investigation 249 



General and metcrological observations 249 



The effects of the freeze on citrus trees and fruits 255 



Effect on citrus trees 255 



Effect on external appearance of fruit 256 



Effect on internal condition of fruit 257 



How to determine the extent of fruit injury 258 



Effect on quality and uses of fruit 259 



Effect on foliage 259 



Effect on wood. 259 



Effect on bark 260 



Relative hardiness of different varieties and species of Citrus fruits 261 



Relative hardiness of trees 261 



Relative hardiness of fruit 263 



Natural factors influencing the temperature 264 



Elevation 264 



Protective hills 265 



Influence of canons 265 



Water protection 265 



Protection afforded fruit by location on tree 265 



Artificial methods of protecting groves 266 



Windbreaks 266 



Effect of running water or irrigating during.freeze 267 



Effect of spraying water on trees 268 



Effect of wrapping trees 268 



Protection by lath houses, burlap or cloth coverings 269 



Protection by artificial heating 270 



Acreage and general results 270 



Equipment and material 270 



Methods 273 



Temperature at which to fire.... 274 



Value of combined effort '. 274 



Causes of failure 274 



Costs of heating 275 



* Paper No. 55, University of California, Graduate School of Tropical Agricul- 

 ture and Citrus Experiment Station, Riverside, Cal. 



210384 



