246 



Principles of Plant Culture. 



The general principle involved is the suppression of 

 growth in all parts that tend to grow beyond the lines of 

 symmetry (Fig. 158). This is best accomplished by 

 pinching (416 a) during the growth period, thus econo- 

 mizing the plant's energy; but when the pinching has 

 been neglected, the shoots that grow out of symmetry 

 may be cut back during the dormant period. 



In pru n i 11 g 

 for symmetry, 

 the plant 

 should gener- 

 ally be encour- 

 aged to develop 

 the form that 

 is natural to 

 the particular 

 species or va- 

 riety; e.g., the 

 American elm 

 tree,* which 

 naturally d e- 

 velops an open, 

 somewhat 

 spreading head 

 tending to be 

 b r o a d e s t to- 

 ward the top, 

 should not be pruned to the same form as the sugar 

 maple f that develops a more roundish and compact head. 

 Evergreens are sometimes pruned to ideal forms, as in 

 topiary work, a practice that is generally condemned by 

 good taste. 



* Ulmus Americana. f Acer saccharinum. 



FIG. 158. Pruning for symmetry. The branches 

 growing beyond the ideal outline, indicated by the 

 dotted line, should be cut off at the points indicated. 



