HOW FAR TO GO IN CAVITY FILLING 



By J. J. Levison, M. F., Forester for the City of New York 



READERS of American Forestry often ask us djjbout 

 cavity filling just how it should be done, and, 

 what is more important, when to do it and When 

 not to do it. We shall now have a heart to heart talk on 

 this question and see if we cannot come to a mutual under- 

 standing on its limitations and advantages. 



Generally speaking, there are two classes of cavities: 

 those which are shallow and afford no chance for the 

 accumulation of moisture and those which are deep and 

 afford opportunity for the accumulation of moisture. 



The treatment of the shallow group of cavities is a 

 very simple one. All soft and decayed wood should be 

 chiseled off so that the water falling on the surface of 

 the wound will naturally run off. The exposed wound 

 should then be thoroughly covered with a coat of coal- 

 tar mixed with creosote; nothing else should be done to 

 it for a year or two, when another coat of tar and creosote 

 may be applied. 



In case of deep cavities 

 where moisture lodges, the 

 treatment is different. With 

 these we must not only elim- 

 inate all decayed and dis- 

 eased wood but we must 

 also fill the cavity or part of 

 it so as to drain water. The 

 absolute elimination of dis- 

 eased wood and the pre- 

 vention of any possible ac- 

 cumulation of moisture are 

 the two main considerations 

 in all cavity filling. This in- 

 volves considerable experi- 

 ence and knowledge of fun- 

 damental principles and for 

 this reason if one has not 

 had enough experience him- 

 self it may often be prefer- 

 able to call upon some one 

 of the tree expert com- 

 panies. Before filling the 

 cavity, the operator should 

 determine whether it is 

 worth doing the work at all 

 or whether it is more prac- 

 ticable to cut the whole 

 tree or branch off. A cavity 

 may be so permeated with 

 disease or so deep or the 

 tree so old and weak that 

 the entire elimination of 

 disease is impossible; also 

 the condition may be such 

 100 



FILLING A TREE CAVITY 



It is essential that every bit of decayed and diseased wood shall be cut or scraped 

 out and also that the cavity is filled so as to drain water, for when this work is 

 improperly done it is wasteful and often injurious. 



that the tree or limb may break soon after the filling is 

 put in. In that case it is wiser to sacrifice the tree and 

 not to fill the cavity. 



Where, however, a filling can be put in with advan- 

 tage, the process should consist in removing all diseased 

 wood from it with the free use of the knife, chisel or gouge. 

 It is far better to enlarge the cavity by cutting out every 

 bit of diseased wood than it is to leave a smaller hole in 

 an unhealthy state. Disease left within the cavity will 

 continue its destructive work behind the filling with more 

 vigor than if there had been no filling at all. Where there 

 are boring insects within the cavity, their destruction 

 must be assured before filling is commenced. 



When the cavity is absolutely freed from disease and 

 insects, its walls should be washed with corrosive sublimate 

 and covered with white lead or with Bordeaux mixture. 

 The interior should be studded with nails and solidly filled 

 with bricks, stones, and cement or with charcoal, bricks, and 



cement. When that is done, 

 the outer edge of the cavity 

 is interlaced with wire to 

 assist in holding the solid 

 material in place, and a 

 layer of cement, mixed with 

 one-third sand, is then 

 placed over the wire. When 

 dry, this layer should be 

 covered with coal-tar. The 

 exposed face of the filling 

 must not be brought out to 

 the same plane with the 

 outer bark of the tree, but 

 should rather recede a little 

 beyond the growing tissue 

 which is situated immedi- 

 ately below the outer bark. 

 By this method the growing 

 tissue will be enabled to ex- 

 tend over the cement and 

 cover the whole cavity, if 

 it be a small one, or else to 

 grow out sufficiently to 

 overlap the filling and hold 

 it as a frame holds a 

 picture. The growth of this 

 living tissue can be much 

 accelerated by cutting 

 around the border of the 

 orifice immediately before 

 the season of growth com- 

 mences. Of the many fail- 

 ures in filling cavities, the 

 great majority are due to 



