UNITED STATES DEPARTMENT OF AGRICULTURE 



m BULLETIN No. 821 *,, 



'^sl|2v>^i^^ Contribution from the Bureaa of Plant Indnstry ^3^ 



^J^'^^Sl WM. A. TAYLOR. Chief ^^^'"^^t. 



Washington, D. C. 



June 4, 1920 



FROST PROTECTION IN LEMON ORCHARDS. 



By A. D. Shamel, Physiologist, L. B. Scott, Pomologisl, and C. S. Pomeroy, Assist- 

 ant Pomologist, Office of Horticultural and Pomological Investigations.^ 



CONTENTS. 



Climatic conditions in the Corona district. . . 



Method of orchard heating 



Objects of the investigations 



Plan of the Investigations 



Method of securing records 



Presentation of data 



Pago. 

 Lessons taught by the investigations in 1913. . 22 

 The behavior of heated and nonheated plats 



in 1914 25 



Comparison of the Eureka and Lisbon vari- 

 eties 27 



10 Summary. 



29 



CLIMATIC CONDITIONS IN THE CORONA DISTRICT. 



ON DECEMBER 25 and 28, 1912, and during January 5, 6, 7, 8, 

 11, 12, 15, 22, and 23, 1913, many lemon trees in California 

 were severely injured by low temperatures and the accompanjong 

 adverse atmospheric conditions, including violent winds and very 

 low relative humidity. As the writers were then stationed in southern 

 California in connection with the citrus-fruit improvement investiga- 

 tions of the United States Department of Agriculture and were 

 spending considerable time in the lemon district near Corona, it 

 seemed advisable to study the effect of these low temperatures in 

 this particular region. 



The maximum and minimum temperatures, the rainfall, and notes 

 upon wind and other climatic conditions for December, 1912, and 

 January and February, 1913, in the immediate region where these 

 studies were made are shown in Table I. These data were gathered 

 in accordance with the rules of the LTnited States Weather Bureau, 

 and- the climatological instruments were housed in a shelter, as shown 



iThe writers are especially indebted to Miss Katharine G. Bonner, of the Office of Horticultural and 

 Pomological Investigations, for the computations and the preparation of the tables in this bulletin. 

 140207°— 20— Bull. 821 1 



