EFFECTS OF FREEZES ON CITRUS IN CALIFORNIA 283 



yearling lemon tops on sour stock (buds had been inserted several 

 inches above the ground) alongside of sour seedlings. While a slight 

 injury to the foliage was the only harm experienced by the latter, 

 the lemon tops were killed, and the frozen wood extended three to 

 four inches down on the sour stock. Similar conditions were found 

 on pomelo stock, while the pomelo seedlings were scarcely touched. 



Individuality of Trees. One of the most pronounced features of 

 the freeze was the greater resistance of some individual trees to frost 

 injury than of other trees, of the same age and kind and growing 

 under the same conditions. This perhaps was more apparent in young 

 orchards than in old ones, and many instances have been seen in which 

 the majority of trees in a young lemon grove have been killed to the 

 bud, while here and there scattered irregularly through the grove 

 were individual trees retaining a certain proportion of green foliage. 

 The same individuality of trees occurs in old groves, but is not always 

 so well defined. 



In no case was it possible to determine whether the escape of 

 these trees from injury was due to accidental conditions, rendering 

 such trees more dormant and thus more resistant, or whether due to 

 inherent frost-resistant qualities. 



TREATMENT OF FROZEN TREES 



Soon after the freeze it became apparent that the citrus groves 

 had been very seriously injured and growers were confronted with 

 many important problems connected with their rejuvenation. No 

 experience was available to serve as a guide, and thus many different 

 methods were tested that appeared to give promise of value. The 

 trees given these different treatments were watched, and it has been 

 possible to reach definite conclusions regarding the value of most of 

 the practices which followed the freeze. 



Binding Loose Bark. In many places where loose bark was bound 

 back to the tree again apparently nothing was gained, for the loosened 

 bark died. Many growers, however, reported that they had trees the 

 bark of which was loose immediately after the freeze but which later 

 reunited with the wood. 



Considerable uncertainty exists regarding most of these reports, 

 but it is probable that some of them are true, inasmuch as there were 

 many examples where the bark had split and separated from the tree 

 without being killed. This bark not only remained alive but devel- 

 oped a layer of wood on its inner surface, and a new bark was devel- 

 oped next to the wood of the tree. 



