BULLETIN 231] WALNUT CULTURE IN CALIFORNIA. 163 



nuts grafted upon them do not grow as well as a rule as those on straight 

 black walnut roots. This subject will be discussed more fully in con- 

 nection with root stocks. 



ROYAL HYBRID WALNUTS. 



The name Royal, as we have explained, was first given by Mr. Bur- 

 bank to a supposed hybrid between the northern California black and 

 Juglans nigra, the eastern black. From the first published description 

 of this variety, however,* it would appear that the staminate parent, 

 supposedly a northern California black walnut, was in reality itself a 

 Royal hybrid, as the illustration of the nut of this tree shows a very 

 rough, small nut which must certainly contain more or less nigra blood. 

 Such trees are quite common about the streets of Santa Rosa. The Bur- 

 bank Royal is presumably, therefore, at least three quarters nigra and 

 one quarter northern California black. 



Following Mr. Burbank's naming of this hybrid, the term Royal has 

 come to be applied in California to all hybrids resulting from crossing 

 between different black walnut species. There are many of these trees 

 in the State, particularly about the older towns like Santa Rosa, San 

 Jose, Vacaville, Winters, Chico, Red Bluff and other points in the Sac- 

 ramento Valley, Stockton, Santa Barbara and other places. It is indeed 

 difficult to find in the State a straight Juglans nigra, except those 

 grown from nuts brought directly from the East. It is rather remark- 

 able that the California species should hybridize so freely with nigra, 

 inasmuch as their blooming periods are quite distinct, the true nigra 

 coming out much later than any other black walnut. Such great varia- 

 tion exists indeed in these seedlings of California nigra trees that in 

 some cases it seems difficult to account for all this variation on the 

 basis of hybridization. For example, there are some nigra trees in the 

 State planted from nuts which came from the East, which have all the 

 charactertistics of the species. They are of slow growth, very late in 

 coming out in the spring, early in shedding their foliage in the fall and 

 bear the typical deep-grooved, sharp-ridged nigra nuts. When nuts 

 from these trees are planted it often happens that almost none of the 

 resulting seedlings are of the true nigra type, but they are hybrids, 

 freaks, variations, mutants, or whatever we may call them. We were 

 at one time inclined to the opinion that such variation was the effect 

 of environment, causing a breaking up of the original species, but 

 further study has brought us to believe that these are really hybrids. 

 We are led to this opinion from the fact that the percentage of these 

 unusual trees varies from year to year and that among the seedlings 



* Supplement to New Creations in Fruits and Flowers, Burbank, 1898. See Pacific 

 Rural Press, Feb. 5, 1898. 



