ARBORICULTURE 



ARBORICULTURE 



355 



grows old, the white pine is likely to bare its trunk in 

 spite of other training. Spruces and other coniferous 

 trees are ruined if pruned to show the trunk. Figs. 

 318, 319. Many deciduous trees are also most attrac- 

 tive when their lower limbs rest on the ground, as 

 beeches, the Norway maples, hornbeams and many 

 more, any tree in fact whose natural habit will permit 

 such a form. 



Old trees, owing to neglect, or more often, improper 

 pruning, frequently need the saw. Protruding stubs 

 should never be left, whether the tree is large or small. 

 The cut should always be made close to the remaining 

 limb and parallel with it. It will not require over two 

 years for the callus to show all around a properly made 

 cut. If it does not show then, the work should be done 

 over again. All dead wood should be kept out. Crossing 

 limbs, even if large, should be removed, A tree should 

 not be dehorned, i.e., cut back to stubs 3 or 4 inches or 

 more in diameter, except as a last resort for a failing 

 tree. 



Pruning is employed for two distinct ends: to train 

 and shape a young tree as it grows; and to re-form or 

 adapt a tree of some maturity, especially if somewhat 

 decrepit. The so-called "tree-doctoring" or "tree- 

 surgery" is applied especially to the latter phase. A tree 

 that has become weakened by transplanting, or from 

 lack of proper nutrition, from lack of proper fertility, or 

 scarcity of water, or from other undetermined causes, 

 may often be forced into active vigorous growth by a 

 severe cutting-back. It may even be allowable, in such 

 cases, to pole or dehorn a tree; that is to remove most of 

 the small limbs, cutting the large ones so close to the 

 tree as to leave stubs as large as one's wrist or arm or 

 even larger. It never happens that several trees in a row 

 need such treatment unless their feeding-ground has 

 been greatly depleted. 



Trees that have been badly pruned, broken by wind, 

 storms or otherwise bruised or mistreated, frequently 

 have badly decayed spots in their trunks and limbs. 

 It has become the custom to "doctor" such trees, 

 that is, thoroughly to clean put rotten wood, treat the 

 exposed surface with a solution of corrosive sublimate 

 or sulfate of copper to kill any fungous growth that 

 may be present, with bisulfide of carbon or other 

 insecticide for insects, and then coat the surface with 

 tar as a preservative. After this the cavity is carefully 

 filled with concrete of the strength commonly used in con- 

 struction work. It is absolutely essential to success that 

 the joint between the wood and cement be water-tight. 

 The surface should also be given a smooth finish of the 

 general outline that the tree would assume had it grown 

 normally. The finished surface should coincide with 

 the inner edge of the cambium layer so that the growth 

 of the tree will proceed over the cement just as it would 

 over a properly cut stub. Zinc caps are frequently 

 used both to cover cement fillings to keep out the 

 water and to cover large cuts when the wood is solid 

 but when it will take several years to heal on account of 

 the size of the wound. Cavities must be absolutely 

 clean, thoroughly disinfected, and the filling positively 

 water-tight or decay will begin behind the filling and 

 the tree will be destroyed while every confidence is 

 being felt that it is safe. The cement work is frequently 

 reinforced with rods of iron. Its principal value is to 

 hold the cement from cracking. The only value of such 

 cement work is as a preventive of decay where there 

 are cavities. When properly done, it gives a smooth 

 surface over which the growth may proceed. The sup- 

 porting value of the cement to the tree is slight. 



\Yith many hardwood trees in important locations 

 such treatment is warranted, but at the present time 

 many trees are thus treated that should be cut down, 

 while many others are left that should have attention. 

 The first requisite to warrant the treatment of a large 

 cavity is a good type of tree in an important location, 

 for example a large tree protecting the home from the 



mid-afternoon sun, or a bad individual in an avenue of 

 otherwise good specimens. In large plantations, treat- 

 ment of a preventive nature is of course warranted, 

 but the filling of large cavities is not worth the cost 

 except to those to whom money is little object. It is 

 better to start new trees than to spend fifty dollars on 

 patching up an old one. One must exercise careful judg- 

 ment in selecting old trees for treatment, to make sure 

 that the tree is worth it. Trees worth doing work on are 

 the oaks, sugar, swamp and Norway maples, hickory, 

 ash, elm and the slow-growing native trees. Those not 

 worth treating in this way are the poplars, willows, 

 silver- and ash-leaved maple and sycamore or plane 



314. Picturesque old apple trees. 



tree. A street tree with a large cavity would better not 

 be doctored unless it is of special value and of a kind 

 likely to last a long time. 



Badly branched trees often show a tendency to split 

 in the crotches. It is well to attend these trees before 

 they begin to split and either chain or bolt the offending 

 limbs together. They may be chained by putting lag- 

 screws in the limbs, drawing the limbs together and 

 dropping a link of the chain over the turned up end of 

 the screw. Rods and turn-buckles may be used in the 

 same way, the bolts for the rods being put through the 

 limbs, not around them. Because bolts have to be 

 placed closer to the weak point than the other reme- 

 dies, they are not so effective but are often useful. If a 

 tree splits, there is danger of decay. The splitting 

 should be anticipated and prevented whenever possible. 



The best time for pruning is not a question of invari- 

 able rule. The period of most active growth, in most 

 places June, is usually regarded as the best time. The 

 period of starting into leaf is probably the worst time, 

 although the maples are about the only good shade 

 trees that seem much affected by pruning at this season. 



Large cuts or wounds should be immediately painted 

 with a good grade of paint or with tar, care being taken 

 to cover the exposed wood but not to allow the paint 

 to come into contact with the cambium layer, or grow- 

 ing part of the bark. 



Root injuries should be as zealously guarded against 

 as injuries to the top. If a large part of the roots must 

 be removed, the top should be correspondingly thinned. 

 Changes of grade are a great source of damage to shade- 

 trees, even when the roots are not actually touched. 

 The filling of 2 or 3 feet of soil over the roots of a tiee is, 

 for most varieties, as sure death to the roots as cutting 

 them off close to the trunk. This filling prevents the 

 aeration of the soil and smothers the soil fife on which 

 healthy root-action seems to depend. This may be 



