182 UNIVERSITY OF CALIFORNIA EXPERIMENT STATION. 



a slaughter, however, just as soon as the tops begin to reach out and 

 touch each other, he should not consider interplanting with walnuts. If 

 double planting is practiced in both directions, using four times the 

 number of permanent trees per acre, the cutting may be extended over 

 at least three years, taking out one fourth of the trees each year. Inter- 

 planting is frequently done with peaches, apricots, grapes, berries and 

 other quick-maturing fruits, also with all sorts of vegetables and annual 

 crops. There is no objection to any of these, so long as the walnut 

 trees are protected from injury and do not suffer for moisture. The 

 latter is one of the greatest dangers and should be carefully guarded 

 against. Interplanting with alfalfa is a common practice and a very 

 desirable one if the alfalfa does not rob the walnut trees of moisture. 

 The latter, however, is frequently the case. In order to guard against 

 this, the walnuts should not depend for irrigation upon the water 

 which they get along with the irrigation of the alfalfa. A cultivated 

 strip should be maintained on each side of the walnut rows and water 

 should be run in separate furrows for the irrigation of the trees. 



CULTURE. 



SOIL HANDLING. 



The various operations of stirring the soil, such as plowing and culti- 

 vating, do not appear to be of as much importance in walnut culture as 

 in the case of some other trees. In relation to the conservation of soil 

 moisture cultivation has its importance, particularly where the water 

 supply is somewhat limited, but given plenty of moisture and suitable 

 soil the walnut tree is one which seems to flourish and produce satisfac- 

 tory crops whether the ground be thoroughly cultivated or not. It is, 

 indeed, a matter of common observation to see large, thrifty walnut trees 

 producing the best of crops while standing in the hard-packed soil of the 

 dooryard or roadside with no cultivation whatever. In fact, trees in 

 such situations seem sometimes to flourish actually better than those in 

 neighboring orchards where some degree of cultivation is practiced. 

 Many growers call attention to trees standing in the dooryard or about 

 the buildings where they receive no cultivation and little or no irriga- 

 tion, which are noticeably in better condition and more productive than 

 trees near by planted in orchard form. The superiority of such trees 

 is not due, however, to their lack of irrigation and cultivation, but rests 

 largely upon the fact that being planted away from other trees they 

 have better exposure to the light and air than trees in the orchard, 

 which appears to be a very essential factor with the walnut. Again, it 

 is true that walnut trees, if they stand in fairly good soil, actually do 

 better without any cultivation than they do if the ground is plowed or 

 cultivated occasionally in a superficial, unsystematic manner. The tree 



