WEEDS AND PLANT DISEASES 



199 



the crop. Hence, the wisest plan is not to have the 

 weeds. Those that do grow should not be allowed 

 to go to seed ; and great care should be taken not to 

 plant weeds with the seeds of the crop. 



Weeds and rotation. - - The system of cultivation 

 and rotation, the kinds of crops raised, and the time 

 of planting and har- 

 vesting may be partly 

 determined by the 

 presence of weeds. 

 The farmer who prac- 

 tices the right system 

 never worries about 

 weeds, for he can usu- 

 ally control them with- 

 out much difficulty. 

 Some crops, as millet, 

 for example, may be 

 planted so early and 

 may grow so quickly 

 that the weeds do not 

 get a chance. Alfalfa, 



which grows rapidly and is cut several times a year, 

 will keep the land free from almost all kinds of weeds. 

 This is especially true after the first year. 



Kinds of weeds. - - There are many kinds of weeds. 

 Ragweeds, cockleburs, purslane, Canada thistles, dan- 

 delions, wild mustard, sorrel, dodder, and jimson weeds 

 are a few of the most common species. What other 



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