346 CITRUS FRUITS AND THEIR CULTURE. 



in spring until all danger of frost injury is passed. It is 

 preferable that the bulk of the nitrogen applied in the fer- 

 tilizer should be given early in spring and that the 

 amounts be gradually lessened in each successive applica- 

 tion as the season progresses. 



Cultivation should not be continued late into the sea- 

 son as it has a tendency to prolong the period of growth. 

 Cutting the surface soil with a cutaway harrow or a shal- 

 low plowing after the cessation of growth, will not affect 

 the trees to any appreciable extent but it must be car- 

 ried too far. 



Liberal amounts of potash have a decided effect on 

 hardening and maturing the new growth, and this feature 

 should not be overlooked in fertilizing. 



Effects of the Stock on the Hardiness of the Top. 

 That there exists a mutual inter-relation between the 

 stock and cion, cannot be doubted. A hardy stock has, 

 in many cases, a marked influence on the power of the cion 

 to withstand cold without injury. 



As pointed out in the chapter on stocks, they vary 

 considerably in their resistance to cold. In order of frost- 

 resistance they may be arranged as follows: trifoliate 

 orange, sour (Bigarade) orange, sweet orange, pomelo 

 and rough lemon. It is probably not too much to say that 

 other things being equal, the hardiness of the tops worked 

 on these stocks will stand in the same order. 



The gain in many cases may be scarcely appreciable, 

 but in others it is well marked. In colder regions, the 

 distinct superiority of sour (Bigarade) orange over rough 

 lemon is quite noticeable, even on young trees, while Citrus 

 trifoliata imparts its hardiness to the top worked upon it 

 to such an extent as to make a very decided difference 

 in its favor. 



