FOREST PROTECTION 109 



CHAPTER III: PROTECTION AGAINST PLANTS. 



Par. 6. Protection Against Weeds, 



Weeds are plants, herbaceous or lignaceous in character, the pre- 

 sence of which in the woods is financially undesirable. 



A. Influencing Factors. 



I. A plant may appear as a weed in one locality whilst 

 it is useful in another. Kalmia, e. g., is useful 

 on steep slopes by holding the soil; whilst it is 

 harmful on areas in regeneration. Grasses and 

 herbaceous weeds are valuable on forest pas- 

 tures; they may interfere, however, with natural 

 regeneration from seeds. 



II. A plant may be considered as a weed at a certain 

 stage of certain sylvicultural operations. This 

 is the case with black gum, witch hazel, box 

 elder, halesia which forms a superstructure in- 

 terfering with the regeneration of yellow poplar, 

 chestnut, and yellow pine. On the other hand, 

 these same species may be valuable as an un- 

 dergrowth or as a companion growth with yel- 

 low poplar, chestnut, pine and oak after the 

 thicket stage. 



III. A plant of a usually valuable kind may be classed 

 as a weed when it is hopelessly deformed; e. g., 

 decrepit, hollow, burned chestnuts; fire shoots 

 of hickory and oak. 



Thus the forester might distmguish between " ab- 

 solute weeds," which are always damaging, and 

 "relative weeds," which are damaging only 

 under a given set of conditions. 



B. Most weeds injure the forest only indirectly. Direct damage is 



done by parasitic weeds, in rare cases. The most note-worthy 

 cases of indirect injury are the following: 



I. Smilax, grapevine, blackberry interfere with the 

 transportation of wood goods and with the ease 

 of access to the woods. 



II. Sedge grass, heather, blueberry form a matting through 

 which water or air cannot pass. 



