2 BULLETIN 1448, U. S. DEPARTMENT OF AGRICULTURE 



Because of the many varying factors which enter into a determina- 

 tion of the best time for picking different varieties and the variation 

 in the tests for best time of picking, it is believed that a detailed dis- 

 cussion of the matter as it relates to the main commercial apple 

 varieties might well be dealt with in a separate bulletin. 



The ripening process in apples consists of numerous changes which 

 take place more or less together, but which may also vary somewhat 

 in their relation to one another. The changes which occur in apples 

 as they ripen on the tree have been dealt with in some detail in a pre- 

 vious publication. 2 Since the discussion in this bulletin will deal 

 very largely, however, with the application of these changes to the 

 time of harvesting of different commercial varieties, it is essential 

 that they be reviewed in this connection. 



CHANGES IN APPLES AS THEY APPROACH PICKING MATURITY 



INCREASE IN SIZE 



Studies on six varieties of apples when growing in various parts of 

 the country have shown 2 that as long as the apples are holding on to 

 the tree a very nearly uniform rate of growth in size continues. 

 Thus, delaying the picking of the apple crop will result in somewhat 

 larger sized fruit. In the tests carried on, the volume of the fruit on 

 the tree increased about 6 to 8 per cent during the 10 days immedi- 

 ately preceding best picking condition. The individual apples, then, 

 are larger if late picking is practiced. A very considerable drop must 

 occur prior to picking before the total tonnage will be materially 

 decreased, as compared with that obtained from earlier picking. 



COLOR OF SEEDS 



The browning of the seeds in apples as they approach picking ma- 

 turity has often been suggested as an index for the best time for 

 picking the fruit. The seeds of the winter apples, however, usually 

 become brown a considerable period prior to the optimum picking 

 date. The time of the coloring of the seeds in relation to the 

 maturity of the fruit varies so greatly with the variety and season 

 that this change is of little value in determining when to pick the 

 fruit. It may be stated, however, that winter apples are practically 

 never ready to pick before the seeds have reached a full brown 

 color. 



CHEMICAL COMPOSITION 



There are marked changes in the chemical composition of apjjles 

 as they approach picking maturity. In general, as the fruit ripens 

 on the tree the astringent substances, including tannin, tend to de- 

 crease, the acidity of the fruit decreases, and there is an increase 

 in sugar content. Because of the wide variations which exist in 

 the chemical composition of apples, aside from those induced by 

 ripening, a chemical test for time of picking appears to be of little 

 practical value. The quantity of sugar will vary with the quantity 



2 Magness, J. R., and Diehl. H. C. physiological studies on apples in storage. 

 Jour. Agr. Research 27 : 1-38, illus. 1924. 



