SHADE TREES. 



205 



mined quite accurately. Sometimes frost cracks open 4 or 5 inches or 



more in winter and close pretty well in summer. They usually extend 



rather deeply into the wood. 

 The best way to treat frost cracks is to staple 



them together. (See Figs. 77 and 78.) Since 



the cracks open more in cold weather than in 



warm, this operation should be done in the spring 



or summer, when the cracks are more or less 



closed. Staples made from iron three-eighths to 



five-eighths of an inch in diameter and 4 to 5 



inches wide, with prongs of the same length, are 



best suited to this purpose. The size of the 



staples depends upon the nature of the frost 



cracks to be treated. In making up the staples it 



is a good idea to have the ends of the prongs bent 



inward a trifle, as they are more likely to hold. 



The staples are driven into the tree at a distance 



of from 15 inches to 2 feet apart, as the case re- 

 quires, and this is best done by first boring holes 



about the size of the staples. The bark and 



wood should be removed sufficiently to allow the 



staples to be driven in flush with the wood, 



and the exposed tissue should be treated with 



some antiseptic substance, such as paint or 



creosote. If it becomes necessary to treat the 



cavity of the frost crack it should be done in 



the winter when the crack is open, and such materials as creosote, coal 



tar and elastic cement or oakum may be employed for this purpose. Dis- 

 infecting the wood is a most important 

 treatment, but filling the crack is of 

 secondary importance and is not abso- 

 lutely necessary. In our experiments the 

 use of staples in large trees has been suc- 

 cessful in holding the crack together so 

 that healing of the tree may follow. If 

 the cracks are not held securely together 

 their constant opening and closing, due to 

 the changes of temperature, rupture the 

 healing tissue and prevent the callus from 

 joining. Trees are sometimes so severely 

 injured by frost cracks that they bleed 

 to death, and we have observed maples 

 that had bled to death in a few weeks 

 from this cause. Occasionally the cracks 



extend from the very top of the tree down to the base, when there is small 



chance of the tree surviving. 



Fig. 77. —Effective method 

 of treating frost cracks 

 liy iron staples. (See 

 Fig. 78.) 



Fig. 78. — Section of tree sliowiug 

 frost cracks and iron staple method 

 of preventing opening, thus facili- 

 tating healing. 



