146 THE PHYSIOLOGY OF PLANTS 



§ 30. When is pruning harmful ? 



It is contrary to good arboriculture to prune a tree too 

 much, so that it is covered with cuts. In our nurseries and 

 gardens trees are often too closely pruned, a procedure which 

 often diminishes productivemess and causes many diseases, not 

 infrequently indeed kills our pyramid trees. 



The excessive pruning is caused as often by too frequent 

 application of the knife as by removing too great an amount 

 of wood. 



We must give the tree an opportunity of developing a few 

 strong woody shoots, which will only be shortened after the 

 wood has ripened and the leaves have fallen, otherwise the tree 

 will become weakened. To remain in good health and eon- 

 tinuously productive, the tree must have a sufficiently large 

 supply of leaves, and these must remain active as long as possible, 

 so as to store up a large amount of food material in the stem. 

 But if every strong shoot is pinched as soon as it exceeds 

 the desired length, and the lateral buds are thus caused to 

 grow out, and if they in their turn have their tips removed, 

 the tree will not have a sufficient supply of well-developed 

 leaves, and a large portion of the food material formed by them 

 will be used up by the developing lateral branches. It must 

 not be forgotten that at the commencement every young shoot 

 draws like a parasite upon the food matter of the older branch ; 

 this applies as much to the consumption of water as to the 

 atored-up food material. The need of a strong root or shoot 

 system for a sufficient supply of foliage is often seen in the 

 case of cordon apple-trees. An exceptionally vigorous leafy 

 shoot will suddenly make its appearance, and if removed, will 

 cause the production of a number of vertically growing 

 suckers. 



Pruning " to excess," however, may also be caused by the 

 untimely removal of older branches, as was formerly often the 

 case in the raising of standard fruit-trees. By cutting away 

 the lateral branches at a very early period, the stem, it is true, 

 would grow very rapidly in height, but the annual rings were 

 only feebly formed, and the stem was often too slender to bear the 



