WEEDS. 163 



CHAPTER VIII. -WEEDS. 



1. In all gardening and agricultural oper- 

 ations the careful cultivator makes it his 

 constant care to destroy weeds. These are 

 wild plants which invade the cultivated land 

 and impede the growth of the crop. Weeds 

 act injuriously in several ways. They crowd 

 out cultivated crops by their leaves overshad- 

 owing and robbing the crop of the necessary 

 sunlight, which, as we have seen, plants make 

 efforts to secure, and which is essential to their 

 growth. The roots of the weeds rob the soil 

 of moisture, thus retarding the crop's growth. 

 At the same time the weeds use up some of 

 the available plant food thus leaving the crop 

 insufficiently fed. This is particularly the case 

 with the nitrogen, as when there are many 

 weeds in the soil their roots compete with 

 those of the crop in taking up the nitrates 

 as fast as they are formed in the soil, and thus 

 the crop may be unable to secure a sufficient 

 supply for the purposes of vigorous growth. 



2. When a piece of land is^newly brought 

 under cultivation much trouble is often expo- 



