CALIFORNIA AVOCADO ASSOCIATION 



67 



one is well aware of the condition the tree weis in prior to the frost can he 

 judge the normal frost resistance of the tree. Anything that has prevented 

 the tree from making a normal growth has aided the cold in its injurious 

 work. These injuries can, in a large majority of cases, be traced to poor 

 soil, hardpan too near the surface, drouth, severe late summer pruning, 

 cultivator injury, lack of cultivation, etc. For example, in the center of 

 a large planting of three year old Harmon trees, I found ten trees with 

 not a trace of injury caused from the fall in temperature to 10 to 20 

 degrees above zero at that point, while the surrounding trees were badly 

 frozen back or killed entirely. It developed that the soil in the field in 

 general had practically no humus and both the surface and subsoil dried 

 out badly and became very hard, but the small plat where the ten uninjured 

 trees stood was of dark loamy soil, apparently very fertile and which 

 retained moisture well. This was in a level field where air drainage could 

 not have been responsible for the condition of this isolated spot. I was 

 of the impression that there had been, in years past, a stable or sheep pen 

 on this fertile spot where the trees were much larger than the surrounding 

 ones, but was told that this was not the case. 



I found a number of cases where vigorous breuiches which had been 

 cut back severely during the fall frosted badly. 



Numerous instances of cultivator injury to branches have also been 

 observed to have resulted in increasing cold injury. Every leaf on branches 

 which were barked on one side by an implement during the last season's 

 cultivation were killed by the cold entirely ; no other leaves on the same tree 

 showing any injury from the cold. Some of these cultivator injuries were 

 so small that one would pass them unnoticed were it not for the frosted 

 leaves. It was observed that not only the condition of the entire tree but 

 even of individual branches determine the amount of resistance to frost. 



In view of this, and many other observations, it seems clear to me 

 that with the great diversification of treatment practiced by orchardmen, 

 and the variation in environment which is found from tree to tree, that we 

 are far from having secured sufficient conclusive evidence to allow us to 

 classify correctly the different varieties so far as cold affects them. 



That the many conditions for thriftiness that affect so markedly the 

 cold resistance of the tree also affects the time of ripening of the crop is 

 probable. Some varieties have not ripened their crop just at the time 

 appointed for them this season, and it seems probable that ripening days 

 should be corelated with the treatment given the tree to determine the 

 normal ripening period. 



Generally speaking, some varieties of the Mexican type have with- 

 stood the past severe winter remarkably well; only the tips of the tender 

 growing branches having been killed by the cold. This condition was 

 observed at different points in Sacramento, San Joaquin, and Santa Clara 

 valleys as well as in this part of the state. Where planted at most desirable 

 elevations and sites, trees of this type are given encouragement. While 

 but few, if any, of the varieties of this type are suitable for commercial 

 planting, they promise something for the home garden and many local 

 markets, especially in parts of the state where there is not a demand for 

 the very high priced fruit and sections which are not sufficiently frost-free 

 to make plantings of the more tender kinds an attractive proposition. The 

 West Indian type promises nothing so far for encouraging their planting 



