WALNUTS 189 



conclusion that lime simply helped to unlock from 

 the soil a certain amount of potassium, phosphoric 

 acid and nitrogen. When these three essential ele- 

 ments were added in fertilizer the lime was not 

 needed at all. 



Persian walnut trees are frequently self-sterile. 

 A single tree standing alone far from its kind may 

 not bear a nut until company is furnished. For that 

 reason it is well to have at least two varieties of the 

 species in any one orchard. Species will sometimes 

 suffice for social purposes instead of varieties. For 

 example, the black walnut hybridizes freely -with the 

 Persian walnut. 



None of the nuts from hybrids between the 

 Persian walnut and other walnuts have as yet shown 

 any especial value, but we have at least one remark- 

 able timber tree resulting from a cross between this 

 species and the California black walnut. 



The Persian walnut comes fairly true to type from 

 seed, but seedling trees are so prone to be unfruit- 

 ful, or to represent inferior ancestors, or to require 

 many years before coming into bearing that nothing 

 but grafted trees should be planted by the orchardist 

 unless he feels that he can afford to experiment. 



BLACK WALNUT 



Which one of our trees is to be the "National 

 Tree" ? The Editor of American Forestry has asked 

 to have the matter put to a vote. The press is now 

 asking readers for expressions of choice. Many 



