160 MASS. EXPERIMENT STATION BULLETIN 170. 



although in the process of development trees need constant attention. 

 It is desirable that antiseptic methods of treatment following pruning, 

 mechanical injuries, etc., shall be adopted. 



Pruning. 



Besides the necessary pruning at the time of transplanting, the removal 

 of dangerous dead wood and branches every two or three years is essential. 



In the case of street trees the lower branches 

 frequently need removing or lightening up. 

 When limbs are so close as to interfere, thin- 

 ning out is necessary to prevent their injuring 

 one another; but tliis thinning may be over- 

 done so as to affect the beauty of the tree. 

 Some make a practice of tliinning and shaping 

 trees when young, thus preventing too much 

 thinning when the tree reaches maturity. The 

 amount of dead wood annually produced in 

 trees is quite large, and it costs about as much 

 to dispose of it as it does to prune it away. 



In towns a distance of 10 or 12 feet or 

 more may be left between the roadway and 

 the lowest limbs, but in cities the nature and 

 amount of traffic necessitate higher pruning. 

 When street trees are growing close together 

 high pruning is often necessary in order to let 

 in sufficient sunlight, and when different types 

 of trees are planted together, such as maples 

 and elms, the pruning is often high in order 

 that the high canopy or Gothic arch effect 

 formed bj^ the elm trees may not be destroyed. 

 If a more or less symmetrical type in indi- 

 vidual specimens is desired, the removal of 

 certain limbs often changes the contour of the trees. We do not believe 

 it desirable to prune the feathery growths often found on the trunks of 

 elms, as they are apparently protective in nature; moreover, in our 

 opinion they add to the beauty of the tree, taking away much of its con- 

 ventional appearance. 



As a rule, the limbs of vigorous maple trees will droop a foot or more a 

 year owing to their increased weight, and in a short time they become 

 too low. Limbs over a sidewalk may be left lower than over roadways. 

 During rain and sleet storms limbs are heavily weighted and often give 

 trouble when too near the ground. 



On country roadsides pruning should be high enough so that the limbs 

 will not interfere with hay and wood traffic. All limbs should be cut as 

 close as possible to the tree, and cuts over 1§ to 2 inches in diameter 



FIG. 20. —Specimen showing 

 poor pruning. Note the long 

 stubs. 



