No. 4.] TREE SURGERY. 457 



the moisture and the outward pressure of the flow, which 

 forces the dressing off the face of the wound in spots, form- 

 ing "blisters" beneath the drying paint or tar. This 

 ' ' bleeding " in itself probably does not greatly sap the vital- 

 ity of the tree, neither does it "poison " the bark below the 

 wound, as has been so frequently asserted ; but pruning at 

 this season often loosens and injures the bark beneath the 

 wound, the sap runs into the cavity thus formed between 

 wood and Imrk, which is kept constantly filled with this 

 watery fluid, which can only induce decay. Another objec- 

 tion urged to s})ring or summer pruning is that it lets in too 

 much sunlight and heat, thereby inducing sun-scald. But if 

 we propose pruning in autumn or winter, we are met with the 

 objection that the wound may be injured by frost ; we must 

 remember, however, that large wounds must withstand the 

 frosts of many winters before they can be healed. Injuries 

 by frost may, and probably do, occur in some regions ; but, 

 having examined thousands of wounds in Massachusetts dur- 

 ing an experience of ten years, I have never yet seen any 

 injury that I could positively attribute entirely to this cause. 

 The effects of sun, rain and drying winds appear to be more 

 serious than those ordinarily experienced from severe or 

 protracted cold. Having had this matter in mind for years, 

 I am led to the belief that trees maj^ be pruned at any sea- 

 son with safet}^ ; but by preference I prune my own trees 

 either in the late fall before the weather becomes too cold 

 to work in comfort, in the late winter, or very early in 

 spring before an}" growth starts. In winter the whole con- 

 formation of the naked tree can be studied much better than 

 in summer when it is covered with foliage. The wounds on 

 most trees at this season are comparatively dry, and there 

 is no ' ' bleeding," therefore the dressing penetrates and 

 adheres well. The bark does not separate readily from 

 the wood in the fall or winter. Still, there are some trees 

 which should not be pruned in late fall or early spring. 

 The American maples are likely to ' ' bleed " if pruned late 

 in the fall, or during warm or moderate \veather in the late 

 winter or early spring. These trees can be pruned mod- 

 erately in July, when the sap no longer flows from the 



