PRUNING PRINCIPLES 87 



82. 5. Plants of the same species or variety vary in habit 

 according to their age, hence must be pruned more or less 

 differently at different ages. 



The tendency for young plants is to make vigorous erect 

 growths rapidly. As they more and more nearly approach 

 the height at which the variety may be said to have reached 

 maturity the more does the rate and extent of growth de- 

 crease. Nothing perhaps has so marked an influence in this 

 respect as fruit bearing. The Kieffer pear, one of the most 

 striking of instances, prior to fruit bearing, shoots upward 

 rapidly and forms an erect tree ; but when fruit bearing be- 

 gins these long limbs bend over and spread the tree often 

 widely. Hence it is necessary to bear Principle S in mind so 

 as to avoid injuring young trees by injudicious pruning. 

 Later when the trees begin to bear or are in full bearing the 

 treatment may be considerably changed to suit the new type 

 of growth. 



83. 6. Severe pruning of the branches favors or increases 

 vegetative growth (i. e., wood production); hence it may 

 be employed to help invigorate iveak plants. 



From plant physiology (Chapter II) it is evident that 

 every plant which is growing normally has a perfect balance 

 between its roots and its top. The root supplies the top 

 with crude food materials and the top supplies the root with 

 elaborated plant food. Thus each furnishes the other with 

 nourishment. As the roots increase in number and extent, 

 therefore, the larger the quantity of crude food taken in the 

 larger must become the leaf development and consequently 

 that of the whole plant. 



Should a considerable amount of the top be removed , for 

 instance, by breakage due to an overload of fruit, or ice, by 

 storm (Fig. 94), by excessive pruning or by such tree 

 butchery as telegraph, telephone and electric linemen and 

 others too often practice (Figs. 64, 65), the amount 

 of crude food taken up by the roots will be distributed 

 in larger proportion to the remaining parts, unless 



