TREE PROTECTION 27 



re&pond readily. In the course of time a nearly normal tree symmetry may be 

 developed by gradually reshaping the outline of profuse dense growth, and later 

 the tree's symmetry may be further improved by grafting if this practice proves 

 necessary. The result will commonly be the production of a dense head growth. 

 To a limited extent, this growth is often an f fifective contribution to the landscape. 



Cavities. Certain general suggestions for the repair of cavities have alieady 

 been indicated. In special cases, complete treatment involving excavation, 

 sterilization, bracing and filling may be desirable, but it is most doubtful whether 

 an inexperienced worker is ever justified m undertaking to complete the entire 

 series of operations independently. In many cases, cavity enlargement can be" 

 checked by removing the obviously diseased wood and sterilizing and protecting 

 the exposed surfaces. It is almost impossible to eliminate all infected wood, but 

 debris and decayed tissue should be removed so as to expose a reasonably sound 

 and smooth wood surface which can be treated with antiseptics and protected 

 with wound dressing as already indicated. Careful consideration should be given 

 to the matter of the ultimate shaping of cavities in order to prevent the accumula- 

 tion of small reservoirs of water. 



Mechanical Support. Any one of a variety of factors may indicate the need 

 for supplying add-tional mechanical support in trees. Specifically, attention 

 has been directed toward the following conditions of a tree and the environment 

 which make bracing advisable: decay, split crotches, weakened sharp-pointed 

 crotches, borer infestation, injured or pruned roots, poor or limited shallow root 

 systems, profuse top growth, proximity of damageable property, exposure to 

 strong wind, or loss of sheltering structures. 



Considerable progress has been made recently by professional tree workers and 

 students of mechanics in the matter of bracing trees. Experimentation and ex- 

 perience have pointed out certain errors in early work (Fig. 13). 



The use of steel rods as rigid braces with or without washers and nuts is com- 

 monly termed bolting of trees. In cases where parts of a tree must be drawn 

 together for bolting, the hole bored for a prescribed screw rod should be larger 

 than the screw rod. Therefore, washers and nuts must be used on both ends of 

 the rod. For other purposes it is evident that holes drilled for screw rods should 

 be rod size or smaller. Holes smaller than rod size should be drilled when washers 

 and nuts are not used on ends of screw rods. In this case dependence is placed 

 upon the grip of the screw rod in the self-threaded channel. When the size of 

 the hole drilled to receive the screw rod is identical with the size of the rod, 

 washers and nuts should be used on both ends of the rod. Screw rods serve in 

 crotch bolting, holding limbs together or apart, and cavity bracing. Also, as 

 "lip bolts", these rods draw together a long split or frost crack in trunk, branch 

 or cavity. Specific conditions will determine the number and location of screw 

 rods needed to insure the relative safeness of trees. 



Steel cable instead of rigid rods is often used for bracing trees. A simple 

 method of cabling employs the fastening of a lag hook or e3'ebolt into each of the 

 two limbs forming a crotch so that the hooks or eyes face each other. The hooks 

 or eyebolts are then tied with steel cable. Where lag hooks are used, provision 

 should be made so that a final quarter turn will make the cable secure. 



When trees require additional structural support, guying may solve the prob- 

 lem. In such cases wires are appropriately affixed to the tree and connected 

 with four strong posts set firmly in the ground on the north, east, south, and 

 west sides. If the guying is temporary, broad bands of leather or other strong 

 material are sometimes wrapped around the tree and supporting wires attached. 



