278 UNIVERSITY OF CALIFORNIA EXPERIMENT STATION 



killed half way to the ground, while trees that had not started were 

 uninjured. In another grove of two-year-old trees some resets, that 

 had been planted in the fall, mere green sticks, were uninjured, while 

 the two-year-old trees all about them were killed to the ground. 



Dryness. It was very common to find trees which on account of 

 being dry were less injured than those which had received more water. 

 If the trees had become so dry during the summer, however, that 

 they had shown the effects of drought, they were often severely in- 

 jured by freezing. In a grove of young trees three or four years old, 

 that had received scant irrigation during the summer, the trees 

 farthest from the head ditch had become, before the freeze, yellow- 

 leafed and looked as if they were dying. These trees were frozen 

 to the ground, but nevertheless most of the trees of this grove were 

 less injured than those in near-by groves that had received more 

 water. Of course it would not be desirable to keep a grove dry and 

 dormant all summer in order that it might live through the winter. 

 These cases are referred to merely to show that dormancy in some 

 cases was induced by dryness, and that it is best not to give a young 

 grove too much water in the fall of the year. 



Irrigation. It was found that even when trees had been well 

 supplied with water during the summer the interval that had elapsed 

 between the freeze and the time of the previous irrigation frequently 

 influenced their hardiness. A number of places were found where all 

 of the factors were the same except the time of irrigation and where 

 there were marked differences in the injury which the differently 

 irrigated portions had sustained. In these cases the trees that had 

 been irrigated about two weeks before the freeze were damaged more 

 than trees which were about six weeks from irrigation. Even when 

 it is likely that all of the trees had their conducting vessels well sup- 

 plied with moisture there was sometimes a difference in condition 

 among these trees corresponding to the differences in the intervals 

 that had elapsed since the previous irrigation. To illustrate, in one 

 grove water was running over the entire grove at the time of the 

 freeze. Most of the grove had not been irrigated before for about 

 six weeks, but a few rows at one side of the grove had been given an 

 extra run of water about two weeks before the freeze. These rows 

 were much more damaged than the rest of the grove. 



While the number of conflicting cases observed make it difficult to 

 deduce any general rules, it seems safe to conclude that trees which 

 were suffering from lack of water and trees that contained the maxi- 

 mum quantity of water were more severely injured than trees that 

 contained a medium amount of water. 



