10 DROUGHT KESISTANCE OF OLIVE IN SOUTHWESTERN STATES. 



manner against the desiccating effects of dry air and intense heat? 

 We may even inquire whether its cycle of growth in rehition to the 

 seasons does not undergo an adjustment adapting itself to periods of 

 drought and rainfall. 



The present bulletin is an attempt to answer such questions in 

 relation to the olive, and the material upon which it is based has been 

 furnished by a number of plantations of olives made in the more arid 

 parts of Arizona and California, where through failure of the irriga- 

 tion systems the trees were thrown on their own resources. It is 

 noteworthy that in all such cases where besides olives other fruit 

 trees were planted, few of the olives died and almost without excep- 

 tion all other fruit trees perished. 



DRY-LAND OLIVE INVESTIGATIONS. 



In the writer's study of the possibilities in dry-land tree growth in 

 southern Arizona and southern California his attention has been 

 called to several cases of abandoned plantations where, along with 

 other fruit and ornamental trees, considerable blocks of olives had been 

 planted. With the failure of the irrigation canals and the consequent 

 cessation of care and culture of the trees, almost all kinds died. 



The survival of the olives, and not only their survival but continued 

 growth and luxuriant appearance, was so notable a feature as to 

 attract the attention of observing ranchmen of the vicinity, for it must 

 be kept in mind that these were localities where irrigation was not 

 simply a convenience, but an absolute necessity to the growing of 

 every crop at present known to them. 



The examples given below showing not the results of careful test 

 and experimentation but results obtained unwittingly and in the face 

 of disaster seem worthy of careful record when studied in the light 

 of the remarkable dry-land olive culture in Tunis, for the first time 

 brought to the attention of this country by Mr. Thomas H. Kearney,*^ 

 of the Bureau of Plant Industry. 



EXAMPLES OF DROUGHT RESISTANCE OF THE OLIVE IN THE 



UNITED STATES. 



AN ABANDONED O^IVE GROVE AT CASA GRANDE, ARIZ. 



The first of the abandoned plantations noted was that known as 

 the Bogart-Degoha ranch, 2 miles south of Casa Grande station in 

 Pinal County, Ariz. (See fig. 1.) The altitude of the station is 

 about 1,396 feet, and the olive orchard is only a few feet higher. 

 The mean annual temperature for the twenty-three years recorded is 

 72° F., and the average annual rainfall is 6.88 inches. 



"Roo " Dry-land Olive Ciiltnro in Northern Afrira," Bnllotin 12,5, Bureau of Plant 

 Industry, U. S. Dept. of Agriculture, 1908. 

 192 



