PRUNING PRINCIPLES 105 



color, we may readily see how greatly summer pruning has decreased 

 the efficiency of the food factory of the plant (29). 



Much of this loss of vigor we expected, but we also expected a 

 compensating increase in fruitfulness. In the old orchard the data 

 are conflicting. In the young orchards we have attempted to corre- 

 late summer pruning with early bearing, but the correlation is nega- 

 tive. Merely corrective dormant pruning far "exceeded all forms 

 of summer pruning in bringing about early bearing, and in some 

 cases the moderate and heavy dormant-pruned blocks produced 

 more bountifully than did the summer-pruned trees. The writer 

 has serious doubts as to the wisdom of deliberately impairing the 

 vigor and the vitality of a tree to throw it into bearing. 



98. /j. A check which does not impair the health or the 

 strength of a 'plant tends to fruitfulness. 



Too severe pruning, over-tillage, a too liberal supply of 

 nitrogenous plant food in the soil, whether due to over- 

 tillage, over-manuring, or the too constant use of leguminous 

 cover crops, all may produce the same effect; excessive 

 wood growth at the expense of the fruiting habit. All but 

 the first of these may be corrected by reverse practices, as 

 already noted (80, 81, 83). The bad effects of heavy prun- 

 ing and how to correct them are also discussed in the same 

 sections. 



Other methods of checking growth, mainly of very local 

 application, depend upon checking the flow of elaborated 

 plant food; for, as already noted (Chapter II), this food, 

 when in abundance, tends to fruit bud development, whereas 

 abundance of crude sap tends to increase wood development. 

 Among the ways adopted to secure this result are notching 

 the stem below a bud to encourage the formation of a fruit 

 spur, and above a bud to secure a long woody twig. Shallow 

 girdling and ringing i. e., no deeper than the cambium 

 favor fruit bud formation above the cut ; when through the 

 cambium and the young wood the girdle favors the pro- 

 duction of woody shoots below it, but generally results in 

 the death of the upper parts of the stem so cut. When the 

 girdle is placed lower on the branch than the leafy area, 

 such twigs as may develop must do so upon the supply of 

 elaborated food stored in the tissues below the wound. If 



