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, pumpkins 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 horticulture, but I am reminded that many people have different 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 forest 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 injuriousness 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 |