jpiS 



BETTEP.FRUIT 



p 



Summer Pruning of a Young Bearing Apple Orchard 



By L. D. Batchelor and W. E. Goodspeed, Riverside, California 



THF majority of horticultural writ- 

 ers seem to favor the summer 

 pruning of apple trees. The prac- 

 tice and the arguments made in its 

 favor vary widely and in some in- 

 stances seem almost contradictory. On 

 (hi' other hand, some experimenters and 

 practical workers have obtained nega- 

 tive results by summer pruning from 

 the viewpoint of crop production and 

 tree growth. Dickens (Kansas State 

 Bulletin 136, p. 181, 1906) caused un- 

 productive ten-year-old apple trees in 

 Kansas to bear satisfactorily during the 

 fourth year of summer pruning. The 

 Gardner's Chronicle (Gardner's Chron- 

 icle, 3, Ser. 11 (19071. No. 1009, pp. 

 400-403, 406, 107) compiled the opinions 

 of more than one hundred and eighty- 

 live fruit growers who practiced sum- 

 mer pruning, and about 82 per cent of 

 these orchardists reported satisfactory 

 results, while the remainder expressed 

 doubts as to the value of the practice. 

 Opinions compiled from English fruit 

 growers by the Journal of Royal Hor- 

 ticultural Society (The Summer Prun- 

 ing of Fruit Trees. Jour. Rov. Hort. 

 Soc. 33, part 2, pp. 487-49!), 1908) 

 showed that the consensus of opinion 

 was uncertain as to the effects of sum- 

 mer pruning and thai much depended 

 upon soil, climate, varieties and season 

 of practice. Drinkard (Ya. Sla. Tech. 

 Bull. 5, p. 119, 191.")) checked wood 

 growth and greatly stimulated the for- 

 mation of fruit buds by summer prun- 

 ing but one year. Vincent (Pruning for 

 Increased Color and Yield, Better Fruit, 

 December, 1915, p. 27) found summer 

 pruning to be profitable in Idaho, as it 

 increased the total yield, size and color 

 of the fruit; these trees were not irri- 

 gated, however. 



The lack of unity on this subject only 

 points out the many factors which 

 must be considered in giving advice on 

 this matter or in planning investiga- 

 tional work which is intended to throw 

 light on this problem. Any treatise on 

 summer pruning of apples must take 

 into consideration many of the follow- 

 ing factors, which will bear directly on 

 the results obtained: Nature of both 

 the summer and winter pruning prac- 

 tice, variety, slock, root development, 

 age of trees, soil and climatic condi- 

 tions. If the orchard is within the irri- 

 gated sections the amount and season 

 of available water must also be consid- 

 ered. Willi these factors in mind the 

 writers planned an investigation on 

 this subject during the summer of 1911. 

 The soil conditions of the orchard 

 were mosl favorable to apple produc- 

 tion, namely, a well drained, deep, rich, 

 sandy loam. The soil was of much the 

 same consistency to a depth of six or 

 eight feet willi a water table about 58 

 feel from the surface. In the virgin 

 state this soil was covered with a heavy 

 growth of sage brush, which vouches 

 for its natural fertility. Since being 

 brought under cultivation it has been 

 devoted to grain, alfalfa, orchard and 

 the growth of sugar beets as a com- 



panion crop to the trees. The soil is in 

 a high state of fertility for the growth 

 of fruit or genera! farm crops. The 

 varieties include the Jonathan and 

 Gano. The trees had been annually 

 pruned during the dormant season and 

 presented an excellent example of vase- 

 shaped trees, a type common to the 

 Intermountain States. The length of 

 the growing season is sutlicient for the 

 production of the late-maturing apples, 

 such as the Gano or Winesap. An 

 abundance of irrigation water is avail- 

 able. It has usually been necessary to 

 water the orchard four times during 

 the latter part of the growing season, 

 from July 1st to September 15th. Much 

 more water could lie used if necessary. 



In outlining the work it was planned 

 to compare plots pruned only in the 

 dormant season, with similar plots 

 pruned during the dormant season and 

 at different intervals during the sum- 

 mer. Nine similar plots were laid off, 

 and pruned as follows: 



Plot 1, to be pruned in February or 

 March, cutting out the cross limbs, 

 crotches, opening up the center, and 

 thinning out the bearing wood of the 

 tree. No limbs to be headed back and 

 no pruning to be done other than at the 

 above season. 



Plot 2, pruned as Plot 1, during Feb- 

 ruary or March, and all the suckers to 

 be removed from the center of the tree 

 from time to time during the summer. 



Plot 3, same as Plot 1, except the ex- 

 cessive growth in the top of the tree is 

 to be cut back to lateral outside limbs 

 in an endeavor to make the tree take a 

 more spreading and less upright form. 



Plot 4, pruned as No. 1, during Feb- 

 ruary and March, and summer pruned 

 in a similar manner to remove suckers 

 and open up the dense growth of the 

 tree during the third week in June. 



Plot 5, pruned similarly to Plot 4, 

 except summer pruning was done the 

 first week in July. 



Plot 0. same as Plot 4, except summer 

 pruning was done the third week in 

 July. 



Plot 7, similar to Plot 4, except sum- 

 mer work was done the first week in 

 August. 



Plot 8, all pruning similar to Plot I, 

 except summer pruning was done the 

 third week in August. 



Plot 9, unpinned. 



Thus live plots were pruned during 

 the summer, one every two weeks inter- 

 val from the third week in June until 

 the third week in August. 



The summer pruning was similar in 

 every way to the nature of the winter 

 pruning. Crossing and parallel limbs 

 were removed, and the fruiting wood 

 thinned out here and there where it 

 seemed to be crowded. In removing 

 water shoots from the center of the 

 tree, the cut was always made close to 

 main limbs and no stubs were ever left. 

 (Pruning the water shoots to stubs has 

 been persistently practiced by some of 

 the orchardists of the locality, bid al- 

 ways with negative results as far as 



crop was concerned, according to all 

 observations the writers have been able 

 to make.) Measurement of the crop 

 production of marketable fruit has been 

 the chief means of determining the 

 effect of the several types of pruning. 

 General notes were also kept on the 

 size and color of the fruit and vigor of 

 the trees. There was sufficient crop of 

 Gano apples to warrant thinning all the 

 plots to a minimum distance of five 

 inches during the years 1912 and 1914. 

 The Jonathans were similarly thinned 

 during the latter season only. 



The crop productions for the Jon- 

 athan plots are shown by Table 1. The 

 variation between Plots 1 and 2 was 

 only slight, the average production per 

 tree for the four years for the above 

 plots being 067 and 645 pounds, re- 

 spectively. Rubbing the water shoots 

 off of Plot 2 had little or no influence 

 on crop production. Water shoots, how- 

 ever, are so much more readily and 

 cheaply removed during the growing 

 season that it will usually pay to re- 

 move them at this time because of the 

 saving in labor. Plot 3, which was 

 pruned to cause the trees to spread as 

 much as possible, averaged 88 pounds 

 less fruit per tree during the four years 

 than Plots 1 and 2, on which no head- 

 ing back was practiced. The summer 

 pruned Plots 4 to 8 averaged 191 pounds 

 of fruit less per tree for the four years 

 than Plots 1 and 2, which were pruned 

 during the dormant period only. The 

 summer-pruned plots also averaged 112 

 pounds of fruit less per tree than the 

 unpruned plots for the four years. 

 Plots 1 to 2, which yere pruned in the 

 ordinary manner during the dormant 

 season only, averaged 79 pounds of 

 fruit per tree more than the unpruned 

 Plot 9. The variation among the total 

 production of the summer pruned 

 Plots 4 to 8 is within the realm of 

 chance except for i'lols li and 1.. which 

 were noticeably low. This was thought 

 to be caused by the fact that these two 

 plots, through causes of no interest 

 here, were more severely pruned dur- 

 ing the summer of 1013 than the other 

 plots in question. 



Turning now to Table II, which 

 shows the crop production of the Gano 

 plots, much the same comparisons and 

 relative results can be seen. Plots 

 1 and 2 varied only as much as might 

 be expected between any equal number 

 of trees picked at random in the 

 orchard. These I wo plots averaged 

 1,055 pounds per tree while Plot 3 aver- 

 aged 905 pounds, or 90 pounds less per 

 tree. This was due in part at least to 

 the character of pruning which aimed 

 to spread the trees id' Plot 3 as much 

 as possible by culling hack the long 

 terminal growth in the tops of the trees. 

 to the lateral branches. The same re- 

 sults were seen on the Jonathan plots. 

 By the continued efforts of trying to 

 make low-spreading Irecs, more of the 

 future fruiting wood was removed, and 

 there was a continual attempt on the 

 part of the trees lo resume their more 



