UNITED STATES DEPARTMENT OF AGRICULTURE 
JS^J^'^^^J-U 
I BULLETIN No. 821 
Contribution from the Bureau of Plant Industry 
WM. A. TAYLOR, Chief 
Washington, D. C. 
June 4, 1920 
FROST PROTECTION IN LEMON ORCHARDS. 
By A. D. Shamel, Physiologist, L. B. Scott, Fomologist, and C. S. Pomeroy, Assist- 
ant Fomologist, 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 
Page. 
1 
3 
5 
7 
9 
10 
Page. 
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 
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 accompanying 
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 United States Weather Bureau, 
and the climatological instruments were housed in a shelter, as shown 
iThe writers are especially indebted to Miss Kiitharine 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 
