B. p. I.— 596. 



DROUGHT RESISTANCE OF THE OLIVE IN 

 THE SOUTHWESTERN STATES. 



INTRODUCTION. 



Olive culture in the United States has passed through many vicis- 

 situdes. Hence, for the fullest knowledge of this industry to-day 

 we should study not only those cases where olive planting has been 

 a financial success, but the frequent instances where a more or less 

 successful growth of olive trees has been obtained without a remuner- 

 ative production of fruit. The olive tree may maintain life and even 

 make considerable growth under conditions of drought and heat so 

 severe that only the most hardy types of desert trees are able to survive 

 them, yet the margin between such a purely vegetative growth and the 

 production of fruit in remunerative quantities may be a very wide 

 one, so wide that to invest money in the planting and care of olive 

 trees on a commercial scale under such conditions would be sheer 



folly. 



Again, it may occur that one olive grove is producing bountifully 

 while another near by, under substantially the same conditions as to 

 temperature, rainfall, and soil may give but a scant return. Here the 

 choice of varieties, the distance of planting, and the methods of cul- 

 ture and pruning, factors all within the control of the grower, may be 

 quite sufficient to explain the difference between success and failure. 



In fact with any given example of olive trees which do not fruit, 

 especially if they are distant from productive trees for comparison, 

 only the closest study and thorough experimentation can determine 

 how narrow the margin may be between thpir present conditions and 

 those of profitable fruit production. 



When any plant of economic value is found to possess great ability 

 to resist drought or heat that fact in itself becomes a matter worth 

 close investigation. How does it obtain its supply of moisture ? By 

 means of deeply penetrating roots or of superficial roots exploring 

 great areas? Has it some provision for the storage of moisture in 

 time of surplus? Does it possess peculiarities of stem or leaf struc- 

 ture by which the small moisture su])ply is conserved to the utmost 

 and the living cells insulatetl and protected in the most effective 

 192 9 



