648 Journal of Agriculture, Yictoria. [11 Nov., 1918. 



APPLE CULTURE IN VICTORIA. 



(Continued from page 462.) 



By J. Farrell, Orchard Supervisor. 

 Gnarl of the Qravenstein Wood. 



Before passing on to the study of the pests and diseases of apple 

 trees and their fruit, it might be well to consider the matter of the 

 undesirable irregularity which appears in the wood of most Gravenstein 

 trees. This objectionable development is commonly known as the 

 " gnarl," or twisting of the wood. The Gravenstein has long been 

 regarded as one of the best and most profitable of apple trees under 

 cultivation in Victoria. This should be a sufficient incentive for all 

 those interested in its cultivation to endeavour to find a means by which 

 the twisting habit may be prevented, or, at least, minimized. 



The gnarled wood is produced by the premature hardening of a 

 lengthy section or sections of the cambium, thus preventing sap activity 

 in these parts. Depressions, which run with the length of the affected 

 stem or branch, are thus formed. The free passage of the sap promotes 

 strong growth in the healthy portions, causing elongated protuberances 

 to apj)ear. These depressions, interspersed with the elevations running 

 longitudinally in the surface of the wood, give it a corrugated appear- 

 ance. This peculiar habit of growth, although generally regarded as 

 being exclusively confined to the Gravenstein, is occasionally noticed in 

 trees of the Missouri Pippin variety. Gnarl in the latter usually 

 supervenes on variety degeneration and general debility, whereas robust 

 specimens of the former are most liable to its attack. 



A high percentage of Gravenstein trees become affected, and tlie 

 twisting of the wood usiially commences early in the life of the trees. In 

 many instances, after a few years' growth, the stem is so extensively cor- 

 rugated, and the sap flow so seriously interrupted, that the whole super- 

 structure collapses for Avant of plant nutriment. When the main arms 

 or sub-leaders only are affected, the stem being healthy, the case is not 

 so serious, because corrugations of the virulent form can bring about 

 the destruction of individual branches only. Scientific pruning will 

 often obviate the production of those undesirable sections or replace 

 them by others of more befitting character. 



Plate 178, Figs. 1 and 2 show specimens of three-year-old Graven- 

 stein wood, and the cross sections cut from the ends of each depict 

 the corrugations even more clearly than do the long sections. When 

 trees suffer from ordinary hardening or tightness of the bark, they are 

 said to be bark-bound. This impediment is often relieved by making 

 longitudinal incisions in the bark with a grafting knife or other suit- 

 able instrument, thus enabling the sap to become more active. Experi- 

 ments have proved, hoAvever, that this treatment of the gnarled wood, 

 instead of bringing about an improvement, rather exaggerates the 

 evil. The specimen illustrated in Fig. 2 (b) shows that the bark did 

 not respond to the incision in the depression, while it opened freely on the 

 swelled parts (a) and (c). This incision was made when the wood was 

 two years old, and the photograph was taken the following year. 



