The Olive in Arizona 497 



COLD 



Well established olive trees withstand comparatively low tempera- 

 tures. Bearing trees at Tucson survived a temperature of 6 degrees 

 F. in 1913; but the outer foliage, buds, and young twigs were injured 

 and bore no fruit the next year. At the same time young trees were 

 frozen to the ground. It is inadvisable to attempt commercial plant- 

 ings where the temperature falls below 15 degrees F. The fruit is 

 injured with temperatures of 24 to 26 degrees F., but the crop is 

 usually harvested before temperatures as low as these begin. Light 

 frosts during blossoming do not injure the crop, but heavy frosts are 

 disastrous. Temperature is perhaps the most important factor • in 

 Arizona in successful olive culture. 



HUMIDITY 



Arizona is especially suited to olive growing on account of its dry 

 climate. The olive has never been able to accustom itself to high 

 atmospheric humidity. In humid climates it is often seriously affected 

 by insects and diseases, and the fruit is late in maturing. Rain at the 

 time of blossoming or ripening of the fruit is a disadvantage, but 

 rains seldom occur during these periods in Arizona. 



TOPOGRAPHY 



Olives succeed at various elevations in the State below 2500 feet. 

 However, the suitability of localities between 2000 and 2500 feet 

 elevation is largely dependent upon local topography. Often a high 

 mesa may be comparatively free from severe freezes, while nearby 

 valleys, on account of poor air drainage, are too cold for olives. The 

 writer has observed a locality having an elevation of 2400 feet where 

 olives are never injured by cold ; whereas a short distance away in a 

 narrow river valley all attempts to establish orchar is have met with 

 failure, because the trees were frosted. On high mesas and foothill 

 slopes the trees bear earlier than in rich valleys ; although in the latter 

 they grow more rapidly and attain larger size. 



SOIL 



The olive is a comparatively shallow-rooted tree, and draws heavily 

 upon the plant food of the surface soil. This does not permit the 

 inference, however, that it will succeed on shallow, barren soils. 



