158 MASS. EXPERIMENT STATION BULLETIN 238 



This statement attempts to summarize the chief economic purpose of grow- 

 ing fruit trees. Wliat sort of a tree will accomplish this purpose? The first 

 step in fruit production is the formation of fruit buds. It seems to be true 

 that fruit bud formation accompanies the accumulation of starch in the tissues. 

 Ample leaf area and good exposure to sunlight are essential to starch forma- 

 tion. If spur leaves are shaded, or if some or all of them are removed, the 

 chances of fruit bud formation are reduced. But if active growth is going on 

 in the vicinity of potential fruit buds, the accumulation of starch is lessened, 

 even though it is being formed in liberal amounts; it is used up in new growth. 

 Hence, to secure fruit buds we must have a large spur leaf area well exposed 

 to sunlight and a relatively early cessation of shoot growth. These conditions 

 are found in trees producing a heavy bloom. 



Not only must there be an accumulation of starch but also an .adequate sup- 

 ply of water and mineral matter, especially nitrogen, coming up from the soil. 

 This must be abundant enough early in the season to insure leaf growth, but it 

 should be restricted soon or it will favor too long continued growth with 

 heavy consumption and lessened accumulation of starch. 



In pruning young trees so as to prepare the way for future fruitfulness the 

 development of many spurs should be the first objective. It has been shown 

 that heading back one-year wood and shading decrease the number of spurs. 

 The converse of this avoiding heading back and securing good exposure to 

 light, should increase the number of spurs. In order to get good light exposure 

 the branches should come out at a fairly wide angle, perhaps from 45° to 90°. 

 The leaves on an upright branch are shaded by the leaves above, and if there 

 are several upright branches they shade each other. It is often claimed that a 

 dense head will so decrease the light exposure as to interfere with fruit bud 

 formation. This may be true, but there is no indication that the rather dense 

 heads of the unpruned trees in this experiment have bloomed less freely than 

 the more open pruned trees. Perhaps the real trouble witii dense trees that 

 fail to bloom well is often a too prolonged period of growth. This results in 

 a heavy blanket of foliage which shades the spur leaves more than would a 

 greater number of shoots making a short annual growth. 



3. To secure the maximum growth commensurate with strength and future 

 fruitfulness. 



The more rapidly young trees grow, the sooner they will be of a size to pro- 

 duce profitable crops. Early bearing may or may not be profitable when it is 

 secured at the expense of growth. It has been shown that a large shoot growth 

 comes through length of growing season rather than through rapid growth. It 

 may be that very late shoot growth is more liable to winter kill, yet we have 

 seen soft tips come through rather severe winter weather without injury. Late 

 cambial activity is more dangerous than late shoot growth. Probably it is not 

 dangerous if tenninal bud formation is delayed until late September or early 

 October, though as has been shown fruit bud formation is likely to be less in 

 such trees. Late growth is sought after in nursery trees, and winter injury to 

 the tips rarely follows though bark splitting at the base of the trunk of late 

 growing trees is often seen when rather severe cold occurs in November. This 

 frequently occurs in Mcintosh, which is one of our hardiest varieties. It seems, 

 then, that a long season of shoot growth in young trees is desirable, but cam- 

 bial activity should cease in late September. Such conditions are brought 

 about by soil management rather than by ordinary pruning. 



There are objections to too rapid growth. It favors upright growth and 

 narrow branch angles. Probably very rapid growth is not desirable the first 



