288 UNIVERSITY OF CALIFORNIA EXPERIMENT STATION 



through the kindness of the Arlington Heights Fruit Company, seven- 

 year-old lemon trees that were rather severely injured were pruned 

 in several different ways. About ten trees were treated by each 

 method, the pruning being done about the middle of March, 1913, 

 thus somewhat over two months after the freeze. Kow 1 was left 

 entirely unpruned. In row 2 the trees were pruned moderately, 

 limbs being removed as far back as they were thought to be injured. 

 In row 3 without reference to injury, the trees were cut back to the 

 principal branches, thus being very severely pruned. In row 4 the 

 trees were cut off below the crown, leaving thus only the trunks. 



No further pruning was given until May, 1914. At this time it 

 was clearly evident that row 1, unpruned, and row 2, lightly pruned, 

 had developed the largest tops and the most fruit, there being no fruit 

 on the other rows. The dead branches on row 1 had up to this time 

 caused no injury and could be easily distinguished and removed. 

 The growth on these trees after pruning seemed to be, as a whole, 

 better, more vigorous, and more fruitful than on any other row, 

 though scarcely any better than row 2. Eow 2, however, required 

 a second severe pruning, the treatment thus being much more expen- 

 sive than the one pruning given row 1. The pruning in rows 3 and 4 

 had clearly been too severe to give the best results. 



The treatment of limbs on which large patches of bark were killed 

 is very perplexing. Where a limb was partially girdled, it was a 

 question how wide a strip of living bark it should have in order to 

 give satisfactory growth. No positive directions can be given regard- 

 ing such variable cases, as judgment must be used in every case. It is 

 thought, in general, that where a limb is more than half girdled, it 

 would be better to remove it and allow a strong new branch to take 

 its place. 



It must be remembered that in pruning frozen trees, it is highly 

 important to treat the large cut surfaces with a fungicide, such as 

 Bordeaux paste or Bordeaux mixture, followed with asphalt paint. 



The results obtained in these experiments correspond entirely with 

 the experience of growers all over the state, and demonstrated con- 

 clusively that early pruning after a freeze is unnecessary, does no 

 good, and increases the expense, as a second pruning is necessitated. 

 It may do damage to some extent, by causing sunburning. Far the 

 best method is to delay the pruning for from five to six months or 

 longer, until the trees have had time to throw out new growth and 

 plainly delimit the dead portion. All necessary pruning can then be 

 done at one time. The early pruning of lightly frozen trees, in lemons 

 especially, is likely to remove uninjured fruit wood and lessen the 

 following crop. 



