CHAPTER I 

 WEEDS: INJURY TO CROPS AND NATURE OF 



What Is a Weed? A weed has been defined as a 

 plant out of place. If we accept this definition, pump- 

 kins growing in a cornfield, if they are not wanted, are 

 weeds ; oats and barley growing in with wheat are to be 

 regarded as weeds. Perhaps we may define " weed " by 

 saying that it is a plant injurious to agriculture and hor- 

 ticulture, but I am reminded that many people have dif- 

 ferent notions in regard to weeds. 



A great many people call every plant a weed the flower 

 of which is not ornamental. The plants found in a for- 

 est would thus be regarded as weeds. As a matter of 

 fact, these very plants found in the forest are important 

 for the forest and cannot be regarded as weeds ; they are 

 a part of that particular plant community. 



Weeds a Money Loss to the Farmer. Weeds are of 

 tremendous economic importance to all tillers of the soil. 

 A crop shortage on many farms in this country is in part 

 due to the growth of weeds. Farmers everywhere could 

 increase their crops at least one-third by preventing the 

 growth of weeds. The loss to farmers in every state 

 would pay the taxes. 



In the fall of 1908 the writer had some of his students 

 make an estimate in different parts of the state of the in- 

 juriousness of weeds to a corn crop. It was found, for 

 instance, that corn fields kept clean produced a one-third 

 larger crop and that an estimate of the loss of corn from 

 the growth of weeds in the state of Iowa amounts to 

 $7,000,000 to $9,000,000 annually. In all of our great 

 crop-producing states the losses are equally great. The 

 injury from weeds in the United States is not far from 



