40 DROUGHT RESISTANCE OF OLIVE IN SOUTHWESTERN STATES. 



about May 1, at mean temperatures of 66° to 71° F., shown by line 

 (7, figure ]0. 



The ohve harvest is noted as beginning from October 8 to 10 and 

 as completed during the latter part of December. The growing 

 period from flower to earliest ripe fruit averages one hundred and 

 sixty-three days at a mean temperature of 81.6° F., giving a sum- 

 mation of 13,314 units, which corresponds very closely with the fig- 

 ures of Caruso and Tablada. Adding the means, 7,050 units from 

 January 1 to May 1, we have a total of 20,364 units. 



For the full maturing of the crop of medium varieties, 24,000 to 

 25,000 units will be needed at this station, while late-maturing sorts 

 will not ripen till well into the winter. Ileferring to the diagram 

 (fig. 10) the line I) indicates 20,364 units, which occur early in October 



Fig. 10.— Diagram showing the monthly means and summation of heat units of places in the olive-growing 

 regions, illustrating the seasonal activity and heat requirements of the olive, arranged from Table IX. 



for Phoenix, late in November for Los Angeles and Fresno, and barely 

 within the year at Bologna, Italy. Caruso states that the latter place 

 is too cool for the olive, on account of the frosts of December and Jan- 

 uary, but that the fruit matures in sunny localities on the hillsides not 

 far from the town. In localities having low summer means but with 

 little or no frost in the winter months, such as San Jose and Santa 

 Barbara, Cal., where the re([uisite number of heat units for the first 

 ripening of the fruits will barely be accumulated b}^ the end of 

 December, the olives may remain on the trees throughout the suc- 

 ceeding winter months. Where the summation of about 21,000 de- 

 grees can not be reached before such low autumn temperatures prevail 

 as will injure the fruit, olive growing should not be undertaken. 



192 



