Akea of possible dey-land olive culture. 30 



Caruso" states that the olive sap begins to stir at a temperature 

 of 10.50° to 11° C. (which is equivalent to 51° to 52° F.) and flowers 

 at 18° to 19° C. (equivalent to 64.4° to 66.2° F.). Accor(hng to this 

 author, we must regard the zero point of the olive as about 51° to 52° 

 F., but the temperature figures in Table IX indicate that for such 

 localities as Palm Springs and Los Angeles in California and Phoenix 

 and Tucson in Arizona the zero point must be somewhat higher, 

 probably 55° to 56° F. 



To ripen the fruit within a period of safety from autumn frosts, 

 there must be a sum of about 16,400 heat units within six or seven 

 months from the starting of vegetation. Allowing seven months 

 this would be equivalent to about 16,400 units from, say, the middle 

 of March. In order to correlate this seasonal estimate with the 

 summation of average annual heat units, as shown in Table IX, 

 we will add to the above sum the number of heat units from January 

 1 to March 15 for Pisa, Italy, a typical olive locality, and we have a 

 summation of 20,070 units, which would throw the olive ripening at 

 Pisa to about November 20. 



Hidalgo Tablada '' gives the temperature for the flowering of the 

 olive at 19° C. (66.2° F.) and states that at Seville this is reached about 

 ]\Iay 1. From that statement, the accumulation of 3,978 units C. 

 (12,376 F., allowing one hundred and sixty-three days) is sufficient to 

 mature the fruit, which will be accomplished early in October, after a 

 growing season of 27.3° C. (81.14° F.) mean temperature. These 

 dates of seasonal activity of the olive can be regarded only as 

 approximations, there being variations due to localities as well as to 

 varieties of fruit. 



Data regarding the olive in relation to climate in the United 

 States are rather meager, but wduit we have coincide in a very inter- 

 esting way with the European observations. 



Figure 10 is a graphical showing of the data of Table IX, summing 

 up the heat units in columns for each locality, the monthl}^ sumrna- 

 tions being carried between the heavy black lines across the chart. 

 The heavy dotted horizontal lines show approximately the seasonal 

 activity of the olive as it relates to these summations. 



The phenological records for the olive at Phoenix, Ariz.,'^ for the 

 year 1907-8 show the average date of full bloom of the olive to be 



a Caruso, G. Dell' Olivo, Turin, 1883, p. 34. 



& Hidalgo Tablada, Jose de. Tratado del Cultivo del Olivo en Espana y Modo de 

 Mejorarlo, Madrid, 1899, p. 74. 



cSee the phenological records for Phoenix, Ariz., for December, 1907 and 1908, 

 in the Arizona section of the Climatological Service of the Weather Bureau, U.S. Dept. 

 of Agriculture. 

 192 



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