BULLETIN 231] 



WALNUT CULTURE IN CALIFORNIA. 



381 



of a root for the walnut. Also the selection of soil upon which to 

 plant this crop. Land having a sandy or gravelly subsoil within four 

 or five feet of the surface should, if possible, be strictly avoided for 

 planting a walnut orchard. The same is true of soil underlaid by 

 hardpan. In any case it is very desirable to blast each hole with 



FIG. 96. Placentia walnut tree on English root, affected by yellows. Trees like 

 that shown in Fig. 63, on southern California black root, are of same age 

 and interplanted alternately with these. 



dynamite before planting in order that the subsoil may be shaken up 

 and easy access of water permitted. No tree already affected with 

 this disease should be grafted, either in the nursery or in the case of 

 black walnut trees planted in orchard form. The pervalence of this 

 trouble is another argument in favor of the hybrid root or the southern 



