THE ERADICATION OF WEEDS 533 



their stringency and efficiency, some states being practically 

 without legal means of weed control. 



METHODS OF ERADICATION 



703. Annual Weeds. One of the most effective means of 

 eradicating annual weeds is to prevent them from producing 

 seeds. As they have no other means of living over from year 

 to year, annual weeds would soon be destroyed if seed pro- 

 duction were entirely prevented. This, of course, is not 

 practical, but every possible means should be used to reduce 

 the number of seeds which mature. Weeds of all kinds are 

 killed very easily when they are small by stirring the soil 

 sufficiently to expose their roots to the sun. Harrowing or 

 disking will destroy weeds soon after the seeds germinate, 

 which perhaps would survive much more severe treatment 

 a few weeks later. The frequent use of the cultivator helps 

 to keep down annual and other weeds in cultivated fields. 

 Various methods of preventing annual weeds from producing 

 seed are suggested in the paragraphs which follow on the 

 treatment of weeds in special crops. 



704. Biennial Weeds. Biennial weeds are neither as 

 numerous nor as difficult to eradicate as the annuals with 

 their great powers of seed production, or the perennials with 

 their persistent roots. Cutting off the plants below the 

 'crown during the first year or at any time in the second before 

 the flowers are produced will kill biennial weeds. Biennial 

 weeds are seldom troublesome in cultivated fields, for they 

 are usually destroyed by plowing. In other locations, the 

 quickest and easiest method is to cut off the plants below the 

 surface of the ground with a small spade. 



705. Perennial Weeds. Cultivation is the most efficient 

 means of destroying perennial weeds. Smothering the 

 roots by preventing them from producing leaves by frequent 



