October 



SCIENTIFIC AGRICULTURE 



47 



simply iudieates that, although we may not 

 be able to determine actual differentiation 

 before July, to influence such deterinina- 

 tion treatment must be given mucli earlier 

 in the season. Crow's trees blossomed about 

 the 27th of May. 



Biennial Bearing. 



Roberts' work has been in connection 

 with alternate bearing. We all know that 

 many trees of many varieties and even 

 many orchards have the bad habit of bear- 

 ing heavily every other year. Formerly it 

 was considered that bearing a heavy crop 

 one year was the reason wh}' a tree could 

 not produce a crop the following season 

 and consequently that thinning the fruit 

 after it had formed on the tree would in- 

 duce regular bearing by lightening the 

 load for the tree that season. This practice 

 has not resulted in regulating biennial 

 bearing, although it is a very valuable 

 feature of orchard management. 



There is more evidence that fruit or blos- 

 som bud formation is due to nutritional 

 conditions within the tree, whic^ cannot be 

 altered late in the season to give any im- 

 mediate relief. 



Roberts was able to prevent blossom bud 

 formation by removiing the leaves from 

 the spur and here is a lesson to those who 

 take little care of the foliage of their trees. 

 Not only do they lessen the crop of the 

 current year but they ruin their chances of 

 a crop the following season. 



Other points brought out in these in- 

 ve.stigations of Roberts and others are 

 worth considering. 



Magn^ss showed that not only do apples 

 produce fruit on spurs, but also on axillary 

 or side buds produced on wood of the 

 previous season's growth and some on 

 terminal growths which could hardly be 

 classed as spurs being too long to fall in 

 that category. At Ottawa we found tliat 

 most varieties when young produced from 

 fifty to seventy-five per cent of their fruit 

 on axillary or terminal buds, whereas 

 these same varieties when older produced 

 a very small proportion of their fruit on 

 these kinds of buds. 



Young Dudley trees produced most of 

 their fruit from terminals and axillaries. 

 young Wealthys produced 60 per cent 

 from these types of buds, and so on. 



The point to be made here is that as 

 these would largely be removed when a 

 severe system of heading back is practised 

 after a tree is three or four years of age, we 

 have another reason added for not adopt- 

 ing too vigorous a system of annual head- 

 ing back. Further that as old trees are 

 not so dependent upon this type of fruit- 

 ing wood, heading back without being car- 

 ried to a point where it would upset the 

 nutritional balance would not lessen mat- 

 erially the actual number of blossom buds 

 by removal. 



Some of the more salient, features in 

 Roberts' work, including those already 

 mentioned, are: (1) that biennial bearing 

 appears to be related to nutritional condi- 

 tions and not to overbearing, and that 

 thinning of the fruit does not give regular 

 bearing, (2) that fruit spurs have a very- 

 short period of growth and that the blos- 

 som buds are formed nearly a year in ad- 

 vance of blossoming, (3) that spurs act 

 largely as individuals, that is, irrespective 

 to a large extent of the rest of the spurs 

 on the tree, (4) that blossom bud forma- 

 tion depends upon nutrition; it is related 

 to spur length, the longer spurs producing 

 blossom buds and the length of the spur 

 being determined by the nutritive elements 

 avilable, (5) biennial bearing is related to 

 spur growth, that is, when all the spurs 

 on a tree are blossoming heavily, as has 

 been pointed out earlier in this paper, no 

 long spur growths for the next year's crop 

 are produced, the spurs not functioning in 

 a vegetative manner to any extent, (6) a 

 full crop of fruit may be borne when 35 

 per cent of the spurs on the tree blossom ; 

 that is, it is not necessary for all the spurs 

 to blossom to set a full crop of fruit, and 

 liere it should be pointed out that the per- 

 centage of blossoms setting fruit is in in- 

 verse ratio to the percentage of spurs blos- 

 soming. In other words, when 20 per cent 

 of the spurs are vegetative or non-fru-iting, 

 only 36.4 per cent of the blossoming spurs 

 set fruit, whereas when 41 to 60 per cent 

 of the total spurs were vegetative. 81 per 

 cent of the blossoming spurs set fruit. 



Think of the needless waste of blo'>m on 

 a tree that is overloaded with it, or one 

 which has all its spurs blossoming. It now 

 remains for us to .see what suggestions may 

 be offered to regulate biennial bearing and 



