12 N. H. Agr. Experiment Station [Bulletin 304 



be significant under the conditions of this experiment. Production 

 was heavy in all plots. It remains to be seen whether or not these trees 

 will all revert to biennial bearing in 1938. This is a very important ques- 

 tion from a practical point of view. It is hoped that the Mcintosh can 

 be maintained in reasonably good annual production by thinning only 

 in those years when weather conditions produce an exceptionally heavy 



set. 



Since it was evident before the blossom period of 1936 that blossoming 

 in the Mcintosh had been controlled to a considerable extent by thin- 

 ning, the experiments were extended in the spring of 1936 to a num- 

 ber of Baldwin trees in Amherst, N. H. At the time of the first visit, 

 three weeks after the blossoms had been thinned by removing three- 

 quarters of the blossom clusters, it was found that practically every 

 fiower in the blossom clusters left on the trees had set fruit. Since this 

 number would produce a heavy crop, all but one fruit was removed from 

 each spur. The results were exceedingly disappointing— blossom bud 

 formation in every case being so low that it was not worthwhile in the 

 spring of 1937 to make counts of the percentage of spurs blossoming. 

 None of the trees had more than one per cent, bloom. 



Another series of 18 heavily laden Baldwin trees was thinned be- 

 tween three and four weeks after the blossom period to about 75 leaves 

 per fruit. This is a rather severe thinning. The average yield of these 

 trees was 236 pounds, while their unthinned controls produced an aver- 

 age of 352 pounds. The size of the apples was increased from 2.63 to 

 2.86 inches diameter, and the proportion of the surface having a good 

 shade of red was raised from 48% to 56%. In spite of this fact blos- 

 som bud formation on both thinned trees and controls was so meager 

 that, on examination in the spring of 1937, it was considered not worth- 

 while to make counts of the fruit spurs to determine the proportion of 

 bloom. It was found at harvest that there was more fruit on the 

 thinned than on the unthinned trees. 



These thinning experiments have demonstrated that removal of the 

 fruit three weeks after bloom has a very definite effect upon blossom 

 bud formation in the Mcintosh but little or none in the Baldwin. The 

 cultural treatment, of course, must make itself felt through some change 

 which it brings about in the nutrition of the tree. It seems clear that 

 in the Baldwin a longer period is required to create this change or a 

 greater change is necessary in order to influence blossom bud formation. 

 In tests incidental to pollination experiments, L. P. Latimer has gath- 

 ered data on the percentage of spurs blossoming in 1936 on individual 

 branches of a single Mcintosh tree, following removal of the blossoms 

 from different proportions of the spurs in 1935. 



Branches in which every spur was allowed to set fruit in 1935 pro- 

 duced no blossoms in 1936. When blossoms were removed from every 

 other spur on the branch, 10.9% of the spurs produced blossoms in 

 1936. With blossoms remaining on only one spur out of four on the 

 branch in 1935, 27.2% of the spurs blossomed in 1936. With only one 

 out of eight spurs containing blossoms in 1935, 49% of the spurs blos- 

 somed in 1936. In the case of the removal of 15 out of 16 of the blos- 

 som spurs, 78% of the spurs bloomed in 1936. As a check certain un- 



